diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ec5d1961f1a1c..bcaa21d9469af 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -27424,11 +27424,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 type = narrowTypeBySwitchOnTypeOf(type, flow.switchStatement, flow.clauseStart, flow.clauseEnd);
             }
             else if (expr.kind === SyntaxKind.TrueKeyword) {
-                const clause = flow.switchStatement.caseBlock.clauses.find((_, index) => index === flow.clauseStart);
-                const clauseExpression = clause && clause.kind === SyntaxKind.CaseClause ? clause.expression : undefined;
-                if (clauseExpression) {
-                    type = narrowType(type, clauseExpression, /*assumeTrue*/ true);
-                }
+                type = narrowTypeBySwitchOnTrue(type, flow.switchStatement, flow.clauseStart, flow.clauseEnd);
             }
             else {
                 if (strictNullChecks) {
@@ -28043,6 +28039,36 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             return getUnionType(map(clauseWitnesses, text => text ? narrowTypeByTypeName(type, text) : neverType));
         }
 
+        function narrowTypeBySwitchOnTrue(type: Type, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number): Type {
+            const defaultIndex = findIndex(switchStatement.caseBlock.clauses, clause => clause.kind === SyntaxKind.DefaultClause);
+            const hasDefaultClause = clauseStart === clauseEnd || (defaultIndex >= clauseStart && defaultIndex < clauseEnd);
+
+            // First, narrow away all of the cases that preceded this set of cases.
+            for (let i = 0; i < clauseStart; i++) {
+                const clause = switchStatement.caseBlock.clauses[i];
+                if (clause.kind === SyntaxKind.CaseClause) {
+                    type = narrowType(type, clause.expression, /*assumeTrue*/ false);
+                }
+            }
+
+            // If our current set has a default, then none the other cases were hit either.
+            // There's no point in narrowing by the the other cases in the set, since we can
+            // get here through other paths.
+            if (hasDefaultClause) {
+                for (let i = clauseEnd; i < switchStatement.caseBlock.clauses.length; i++) {
+                    const clause = switchStatement.caseBlock.clauses[i];
+                    if (clause.kind === SyntaxKind.CaseClause) {
+                        type = narrowType(type, clause.expression, /*assumeTrue*/ false);
+                    }
+                }
+                return type;
+            }
+
+            // Now, narrow based on the cases in this set.
+            const clauses = switchStatement.caseBlock.clauses.slice(clauseStart, clauseEnd);
+            return getUnionType(map(clauses, clause => clause.kind === SyntaxKind.CaseClause ? narrowType(type, clause.expression, /*assumeTrue*/ true) : neverType));
+        }
+
         function isMatchingConstructorReference(expr: Expression) {
             return (isPropertyAccessExpression(expr) && idText(expr.name) === "constructor" ||
                 isElementAccessExpression(expr) && isStringLiteralLike(expr.argumentExpression) && expr.argumentExpression.text === "constructor") &&
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue.symbols
deleted file mode 100644
index 6461b7c88b263..0000000000000
--- a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue.symbols
+++ /dev/null
@@ -1,144 +0,0 @@
-//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue.ts] ////
-
-=== narrowByClauseExpressionInSwitchTrue.ts ===
-// https://github.com/microsoft/TypeScript/issues/37178
-
-type A = { type: "A" };
->A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue.ts, 0, 0))
->type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 10))
-
-type B = { type: "B" };
->B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 23))
->type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 10))
-
-type AorB = A | B;
->AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 23))
->A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue.ts, 0, 0))
->B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 23))
-
-const isA = (x: AorB): x is A => x.type === "A";
->isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue.ts, 6, 5))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 6, 13))
->AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 23))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 6, 13))
->A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue.ts, 0, 0))
->x.type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 10))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 6, 13))
->type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 10))
-
-const isB = (x: AorB): x is B => x.type === "B";
->isB : Symbol(isB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 5))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 13))
->AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 23))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 13))
->B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 23))
->x.type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 10))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 13))
->type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 10))
-
-function test1(x: AorB) {
->test1 : Symbol(test1, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 48))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 9, 15))
->AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 23))
-
-  switch (true) {
-    case isA(x):
->isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue.ts, 6, 5))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 9, 15))
-
-      x;
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 9, 15))
-
-      break;
-    case isB(x):
->isB : Symbol(isB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 5))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 9, 15))
-
-      x;
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 9, 15))
-
-      break;
-  }
-}
-
-function test2(x: AorB) {
->test2 : Symbol(test2, Decl(narrowByClauseExpressionInSwitchTrue.ts, 18, 1))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 20, 15))
->AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 3, 23))
-
-  switch (true) {
-    case isA(x):
->isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue.ts, 6, 5))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 20, 15))
-
-      x;
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 20, 15))
-
-    // fallthrough
-    case isB(x):
->isB : Symbol(isB, Decl(narrowByClauseExpressionInSwitchTrue.ts, 7, 5))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 20, 15))
-
-      x;
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 20, 15))
-
-      break;
-  }
-}
-
-let x: string | undefined;
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 31, 3))
-
-switch (true) {
-  case typeof x !== "undefined":
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 31, 3))
-
-    x.trim();
->x.trim : Symbol(String.trim, Decl(lib.es5.d.ts, --, --))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 31, 3))
->trim : Symbol(String.trim, Decl(lib.es5.d.ts, --, --))
-}
-
-type SomeType = { type: "SomeType" };
->SomeType : Symbol(SomeType, Decl(narrowByClauseExpressionInSwitchTrue.ts, 36, 1))
->type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue.ts, 38, 17))
-
-declare function isSomeType(x: unknown): x is SomeType;
->isSomeType : Symbol(isSomeType, Decl(narrowByClauseExpressionInSwitchTrue.ts, 38, 37))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 39, 28))
->x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue.ts, 39, 28))
->SomeType : Symbol(SomeType, Decl(narrowByClauseExpressionInSwitchTrue.ts, 36, 1))
-
-function processInput(input: string | RegExp | SomeType) {
->processInput : Symbol(processInput, Decl(narrowByClauseExpressionInSwitchTrue.ts, 39, 55))
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
->RegExp : Symbol(RegExp, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
->SomeType : Symbol(SomeType, Decl(narrowByClauseExpressionInSwitchTrue.ts, 36, 1))
-
-  switch (true) {
-    case typeof input === "string":
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
-
-      input;
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
-
-      break;
-    case input instanceof RegExp:
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
->RegExp : Symbol(RegExp, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
-
-      input;
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
-
-      break;
-    case isSomeType(input):
->isSomeType : Symbol(isSomeType, Decl(narrowByClauseExpressionInSwitchTrue.ts, 38, 37))
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
-
-      input;
->input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue.ts, 41, 22))
-
-      break;
-  }
-}
-
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue1.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue1.symbols
new file mode 100644
index 0000000000000..3892a6c7fddf4
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue1.symbols
@@ -0,0 +1,144 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue1.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue1.ts ===
+// https://github.com/microsoft/TypeScript/issues/37178
+
+type A = { type: "A" };
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 0, 0))
+>type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 10))
+
+type B = { type: "B" };
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 23))
+>type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 10))
+
+type AorB = A | B;
+>AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 23))
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 0, 0))
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 23))
+
+const isA = (x: AorB): x is A => x.type === "A";
+>isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 6, 5))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 6, 13))
+>AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 23))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 6, 13))
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 0, 0))
+>x.type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 10))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 6, 13))
+>type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 10))
+
+const isB = (x: AorB): x is B => x.type === "B";
+>isB : Symbol(isB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 5))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 13))
+>AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 23))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 13))
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 23))
+>x.type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 10))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 13))
+>type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 10))
+
+function test1(x: AorB) {
+>test1 : Symbol(test1, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 48))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 9, 15))
+>AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 23))
+
+  switch (true) {
+    case isA(x):
+>isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 6, 5))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 9, 15))
+
+      x;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 9, 15))
+
+      break;
+    case isB(x):
+>isB : Symbol(isB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 5))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 9, 15))
+
+      x;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 9, 15))
+
+      break;
+  }
+}
+
+function test2(x: AorB) {
+>test2 : Symbol(test2, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 18, 1))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 20, 15))
+>AorB : Symbol(AorB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 3, 23))
+
+  switch (true) {
+    case isA(x):
+>isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 6, 5))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 20, 15))
+
+      x;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 20, 15))
+
+    // fallthrough
+    case isB(x):
+>isB : Symbol(isB, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 7, 5))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 20, 15))
+
+      x;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 20, 15))
+
+      break;
+  }
+}
+
+let x: string | undefined;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 31, 3))
+
+switch (true) {
+  case typeof x !== "undefined":
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 31, 3))
+
+    x.trim();
+>x.trim : Symbol(String.trim, Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 31, 3))
+>trim : Symbol(String.trim, Decl(lib.es5.d.ts, --, --))
+}
+
+type SomeType = { type: "SomeType" };
+>SomeType : Symbol(SomeType, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 36, 1))
+>type : Symbol(type, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 38, 17))
+
+declare function isSomeType(x: unknown): x is SomeType;
+>isSomeType : Symbol(isSomeType, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 38, 37))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 39, 28))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 39, 28))
+>SomeType : Symbol(SomeType, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 36, 1))
+
+function processInput(input: string | RegExp | SomeType) {
+>processInput : Symbol(processInput, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 39, 55))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+>RegExp : Symbol(RegExp, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>SomeType : Symbol(SomeType, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 36, 1))
+
+  switch (true) {
+    case typeof input === "string":
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+
+      input;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+
+      break;
+    case input instanceof RegExp:
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+>RegExp : Symbol(RegExp, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+      input;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+
+      break;
+    case isSomeType(input):
+>isSomeType : Symbol(isSomeType, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 38, 37))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+
+      input;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue1.ts, 41, 22))
+
+      break;
+  }
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue1.types
similarity index 90%
rename from tests/baselines/reference/narrowByClauseExpressionInSwitchTrue.types
rename to tests/baselines/reference/narrowByClauseExpressionInSwitchTrue1.types
index f8a1d9bc87e42..fa20aae9246ba 100644
--- a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue.types
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue1.types
@@ -1,6 +1,6 @@
-//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue.ts] ////
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue1.ts] ////
 
-=== narrowByClauseExpressionInSwitchTrue.ts ===
+=== narrowByClauseExpressionInSwitchTrue1.ts ===
 // https://github.com/microsoft/TypeScript/issues/37178
 
 type A = { type: "A" };
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue10.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue10.symbols
new file mode 100644
index 0000000000000..2abb5fc5d41ec
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue10.symbols
@@ -0,0 +1,107 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue10.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue10.ts ===
+function foo(cond1: boolean, cond2: boolean) {
+>foo : Symbol(foo, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 0))
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 13))
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+    switch (true) {
+        case cond1 || cond2:
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 13))
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+            cond1; // boolean
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 13))
+
+            //  ^?
+            cond2; // boolean
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+            //  ^?
+            break;
+
+        case cond2:
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+            cond1; // false
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 13))
+
+            //  ^?
+            cond2;; // never
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+            //  ^?
+            break;
+
+        default:
+            cond1; // false
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 13))
+
+            //  ^?
+            cond2; // false
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+            //  ^?
+            break;
+    }
+
+    cond1; // boolean
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 13))
+
+    //  ^?
+    cond2; // boolean
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 0, 28))
+
+    //  ^?
+}
+
+function blah(cond1: boolean, cond2: boolean) {
+>blah : Symbol(blah, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 28, 1))
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 14))
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+    if (cond1 || cond2) {
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 14))
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+        cond1; // boolean
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 14))
+
+        //  ^?
+        cond2; // boolean
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+        //  ^?
+    } else if (cond2) {
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+        cond1; // false
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 14))
+
+        //  ^?
+        cond2; // never
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+        //  ^?
+    } else {
+        cond1; // false
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 14))
+
+        //  ^?
+        cond2; // false
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+        //  ^?
+    }
+
+    cond1; // boolean
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 14))
+
+    //  ^?
+    cond2; // boolean
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue10.ts, 30, 29))
+
+    //  ^?
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue10.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue10.types
new file mode 100644
index 0000000000000..d6e8cedfdc64e
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue10.types
@@ -0,0 +1,111 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue10.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue10.ts ===
+function foo(cond1: boolean, cond2: boolean) {
+>foo : (cond1: boolean, cond2: boolean) => void
+>cond1 : boolean
+>cond2 : boolean
+
+    switch (true) {
+>true : true
+
+        case cond1 || cond2:
+>cond1 || cond2 : boolean
+>cond1 : boolean
+>cond2 : boolean
+
+            cond1; // boolean
+>cond1 : boolean
+
+            //  ^?
+            cond2; // boolean
+>cond2 : boolean
+
+            //  ^?
+            break;
+
+        case cond2:
+>cond2 : boolean
+
+            cond1; // false
+>cond1 : false
+
+            //  ^?
+            cond2;; // never
+>cond2 : never
+
+            //  ^?
+            break;
+
+        default:
+            cond1; // false
+>cond1 : false
+
+            //  ^?
+            cond2; // false
+>cond2 : false
+
+            //  ^?
+            break;
+    }
+
+    cond1; // boolean
+>cond1 : boolean
+
+    //  ^?
+    cond2; // boolean
+>cond2 : boolean
+
+    //  ^?
+}
+
+function blah(cond1: boolean, cond2: boolean) {
+>blah : (cond1: boolean, cond2: boolean) => void
+>cond1 : boolean
+>cond2 : boolean
+
+    if (cond1 || cond2) {
+>cond1 || cond2 : boolean
+>cond1 : boolean
+>cond2 : boolean
+
+        cond1; // boolean
+>cond1 : boolean
+
+        //  ^?
+        cond2; // boolean
+>cond2 : boolean
+
+        //  ^?
+    } else if (cond2) {
+>cond2 : false
+
+        cond1; // false
+>cond1 : false
+
+        //  ^?
+        cond2; // never
+>cond2 : never
+
+        //  ^?
+    } else {
+        cond1; // false
+>cond1 : false
+
+        //  ^?
+        cond2; // false
+>cond2 : false
+
+        //  ^?
+    }
+
+    cond1; // boolean
+>cond1 : boolean
+
+    //  ^?
+    cond2; // boolean
+>cond2 : boolean
+
+    //  ^?
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue2.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue2.symbols
new file mode 100644
index 0000000000000..8ce5e2928f487
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue2.symbols
@@ -0,0 +1,49 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue2.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue2.ts ===
+// https://github.com/microsoft/TypeScript/issues/55986
+
+declare const f: 'a' | 'b' | 'c';
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+switch(true) {
+    case f === 'a':
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+    case f === 'b':
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+        f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+        break
+    default:
+        f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+}
+
+f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+switch(true) {
+    case f === 'a':
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+        f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+    case f === 'b':
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+        f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
+        break
+    default:
+        f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+}
+
+f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue2.ts, 2, 13))
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue2.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue2.types
new file mode 100644
index 0000000000000..d1637eb248fd5
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue2.types
@@ -0,0 +1,61 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue2.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue2.ts ===
+// https://github.com/microsoft/TypeScript/issues/55986
+
+declare const f: 'a' | 'b' | 'c';
+>f : "a" | "b" | "c"
+
+switch(true) {
+>true : true
+
+    case f === 'a':
+>f === 'a' : boolean
+>f : "a" | "b" | "c"
+>'a' : "a"
+
+    case f === 'b':
+>f === 'b' : boolean
+>f : "a" | "b" | "c"
+>'b' : "b"
+
+        f;
+>f : "a" | "b"
+
+        break
+    default:
+        f;
+>f : "c"
+}
+
+f;
+>f : "a" | "b" | "c"
+
+switch(true) {
+>true : true
+
+    case f === 'a':
+>f === 'a' : boolean
+>f : "a" | "b" | "c"
+>'a' : "a"
+
+        f;
+>f : "a"
+
+    case f === 'b':
+>f === 'b' : boolean
+>f : "a" | "b" | "c"
+>'b' : "b"
+
+        f;
+>f : "a" | "b"
+
+        break
+    default:
+        f;
+>f : "c"
+}
+
+f;
+>f : "a" | "b" | "c"
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.errors.txt b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.errors.txt
new file mode 100644
index 0000000000000..cec1802a21fcf
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.errors.txt
@@ -0,0 +1,32 @@
+narrowByClauseExpressionInSwitchTrue3.ts(12,9): error TS2367: This comparison appears to be unintentional because the types '"square"' and '"circle"' have no overlap.
+narrowByClauseExpressionInSwitchTrue3.ts(13,32): error TS2339: Property 'radius' does not exist on type 'never'.
+narrowByClauseExpressionInSwitchTrue3.ts(15,14): error TS2367: This comparison appears to be unintentional because the types '"square"' and '"circle"' have no overlap.
+
+
+==== narrowByClauseExpressionInSwitchTrue3.ts (3 errors) ====
+    type Shape =
+        | { kind: "circle", radius: number }
+        | { kind: "square", sideLength: number }
+    
+    function wat(shape: Shape) {
+        switch (true) {
+            case shape.kind === "circle":
+                return Math.PI * shape.radius ** 2;
+            case shape.kind === "circle": // should error
+        }
+    
+        if (shape.kind === "circle") {
+            ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2367: This comparison appears to be unintentional because the types '"square"' and '"circle"' have no overlap.
+            return Math.PI * shape.radius ** 2;
+                                   ~~~~~~
+!!! error TS2339: Property 'radius' does not exist on type 'never'.
+        }
+        else if (shape.kind === "circle") {
+                 ~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2367: This comparison appears to be unintentional because the types '"square"' and '"circle"' have no overlap.
+            //         ~~~~
+            // Property 'kind' does not exist on type 'never'.
+        }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.symbols
new file mode 100644
index 0000000000000..b6811492524e1
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.symbols
@@ -0,0 +1,60 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue3.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue3.ts ===
+type Shape =
+>Shape : Symbol(Shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 0, 0))
+
+    | { kind: "circle", radius: number }
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 7))
+>radius : Symbol(radius, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 23))
+
+    | { kind: "square", sideLength: number }
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+>sideLength : Symbol(sideLength, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 23))
+
+function wat(shape: Shape) {
+>wat : Symbol(wat, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 44))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+>Shape : Symbol(Shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 0, 0))
+
+    switch (true) {
+        case shape.kind === "circle":
+>shape.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 7), Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 7), Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+
+            return Math.PI * shape.radius ** 2;
+>Math.PI : Symbol(Math.PI, Decl(lib.es5.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>PI : Symbol(Math.PI, Decl(lib.es5.d.ts, --, --))
+>shape.radius : Symbol(radius, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 23))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+>radius : Symbol(radius, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 23))
+
+        case shape.kind === "circle": // should error
+>shape.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 7), Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 1, 7), Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+    }
+
+    if (shape.kind === "circle") {
+>shape.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+
+        return Math.PI * shape.radius ** 2;
+>Math.PI : Symbol(Math.PI, Decl(lib.es5.d.ts, --, --))
+>Math : Symbol(Math, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>PI : Symbol(Math.PI, Decl(lib.es5.d.ts, --, --))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+    }
+    else if (shape.kind === "circle") {
+>shape.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+>shape : Symbol(shape, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 4, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue3.ts, 2, 7))
+
+        //         ~~~~
+        // Property 'kind' does not exist on type 'never'.
+    }
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.types
new file mode 100644
index 0000000000000..1fde85a02984d
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue3.types
@@ -0,0 +1,77 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue3.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue3.ts ===
+type Shape =
+>Shape : { kind: "circle"; radius: number; } | { kind: "square"; sideLength: number; }
+
+    | { kind: "circle", radius: number }
+>kind : "circle"
+>radius : number
+
+    | { kind: "square", sideLength: number }
+>kind : "square"
+>sideLength : number
+
+function wat(shape: Shape) {
+>wat : (shape: Shape) => number | undefined
+>shape : Shape
+
+    switch (true) {
+>true : true
+
+        case shape.kind === "circle":
+>shape.kind === "circle" : boolean
+>shape.kind : "circle" | "square"
+>shape : Shape
+>kind : "circle" | "square"
+>"circle" : "circle"
+
+            return Math.PI * shape.radius ** 2;
+>Math.PI * shape.radius ** 2 : number
+>Math.PI : number
+>Math : Math
+>PI : number
+>shape.radius ** 2 : number
+>shape.radius : number
+>shape : { kind: "circle"; radius: number; }
+>radius : number
+>2 : 2
+
+        case shape.kind === "circle": // should error
+>shape.kind === "circle" : boolean
+>shape.kind : "circle" | "square"
+>shape : Shape
+>kind : "circle" | "square"
+>"circle" : "circle"
+    }
+
+    if (shape.kind === "circle") {
+>shape.kind === "circle" : boolean
+>shape.kind : "square"
+>shape : { kind: "square"; sideLength: number; }
+>kind : "square"
+>"circle" : "circle"
+
+        return Math.PI * shape.radius ** 2;
+>Math.PI * shape.radius ** 2 : number
+>Math.PI : number
+>Math : Math
+>PI : number
+>shape.radius ** 2 : number
+>shape.radius : any
+>shape : never
+>radius : any
+>2 : 2
+    }
+    else if (shape.kind === "circle") {
+>shape.kind === "circle" : boolean
+>shape.kind : "square"
+>shape : { kind: "square"; sideLength: number; }
+>kind : "square"
+>"circle" : "circle"
+
+        //         ~~~~
+        // Property 'kind' does not exist on type 'never'.
+    }
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue4.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue4.symbols
new file mode 100644
index 0000000000000..c505b1d47c975
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue4.symbols
@@ -0,0 +1,21 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue4.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue4.ts ===
+declare const f: 'a' | 'b' | 'c';
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue4.ts, 0, 13))
+
+switch (true) {
+  case f === "a":
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue4.ts, 0, 13))
+
+  default:
+    f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue4.ts, 0, 13))
+
+  case f === "b":
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue4.ts, 0, 13))
+
+    f;
+>f : Symbol(f, Decl(narrowByClauseExpressionInSwitchTrue4.ts, 0, 13))
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue4.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue4.types
new file mode 100644
index 0000000000000..8dc6062a2b695
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue4.types
@@ -0,0 +1,27 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue4.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue4.ts ===
+declare const f: 'a' | 'b' | 'c';
+>f : "a" | "b" | "c"
+
+switch (true) {
+>true : true
+
+  case f === "a":
+>f === "a" : boolean
+>f : "a" | "b" | "c"
+>"a" : "a"
+
+  default:
+    f;
+>f : "a" | "c"
+
+  case f === "b":
+>f === "b" : boolean
+>f : "a" | "b" | "c"
+>"b" : "b"
+
+    f;
+>f : "a" | "b" | "c"
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue5.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue5.symbols
new file mode 100644
index 0000000000000..3c890662516f5
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue5.symbols
@@ -0,0 +1,304 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue5.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue5.ts ===
+type A = { kind: "A", value: number };
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 0))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10))
+>value : Symbol(value, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 21))
+
+type B = { kind: "B", name: string };
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 38))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+>name : Symbol(name, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 21))
+
+type C = { kind: "C", cond: boolean };
+>C : Symbol(C, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 37))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10))
+>cond : Symbol(cond, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 21))
+
+type D = { kind: "D", value: boolean };
+>D : Symbol(D, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 38))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10))
+>value : Symbol(value, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 21))
+
+type E = { kind: "E", x: number, y: number };
+>E : Symbol(E, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 39))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 21))
+>y : Symbol(y, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 32))
+
+type All = A | B | C | D | E;
+>All : Symbol(All, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 45))
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 0))
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 38))
+>C : Symbol(C, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 37))
+>D : Symbol(D, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 38))
+>E : Symbol(E, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 39))
+
+function fn1switch(input: All) {
+>fn1switch : Symbol(fn1switch, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 6, 29))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+>All : Symbol(All, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 45))
+
+    switch (true) {
+        case input.kind === "A":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        case input.kind === "B":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+            if (input.kind === "A") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+
+                return;
+            }
+
+            input; // Should be B;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+
+            //  ^?
+
+            // fallthrough
+        case input.kind === "C":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+            input; // Should be B | C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+
+            //  ^?
+            break;
+        default:
+            input; // Should be D | E
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+
+            //  ^?
+    }
+
+    input; // Should not be A
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 8, 19))
+
+    //  ^?
+}
+
+function fn1ifelse(input: All) {
+>fn1ifelse : Symbol(fn1ifelse, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 31, 1))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+>All : Symbol(All, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 45))
+
+    if (input.kind === "A" || input.kind === "B") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        if (input.kind === "A") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+
+            return;
+        }
+
+        input; // Should be B;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+
+        //  ^?
+    }
+    if (input.kind === "C" || input.kind === "B") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        input; // Should be B | C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+
+        //  ^?
+    }
+    else {
+        input; // Should be D | E
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+
+        //  ^?
+    }
+
+    input; // Should not be A
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 33, 19))
+
+    //  ^?
+}
+
+function fn2switch(input: All) {
+>fn2switch : Symbol(fn2switch, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 53, 1))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+>All : Symbol(All, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 45))
+
+    switch (true) {
+        case input.kind === "A":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        case input.kind === "B":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+            if (input.kind === "A") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+
+                return;
+            }
+
+            input; // Should be B;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+
+            //  ^?
+
+            // fallthrough
+        case input.kind === "C":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+            input; // Should be B | C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+
+            //  ^?
+            break;
+        default:
+            input; // Should be D | E
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+
+            //  ^?
+            return;
+    }
+
+    input; // Should be B | C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 55, 19))
+
+    //  ^?
+}
+
+function fn2ifelse(input: All) {
+>fn2ifelse : Symbol(fn2ifelse, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 79, 1))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+>All : Symbol(All, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 45))
+
+    if (input.kind === "A" || input.kind === "B") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        if (input.kind === "A") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+
+            return;
+        }
+
+        input; // Should be B;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+
+        //  ^?
+    }
+    if (input.kind === "C" || input.kind === "B") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        input; // Should be B | C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+
+        //  ^?
+    }
+    else {
+        input; // Should be D | E
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+
+        //  ^?
+        return;
+    }
+
+    input; // Should be B | C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 81, 19))
+
+    //  ^?
+}
+
+function fn3switch(input: All) {
+>fn3switch : Symbol(fn3switch, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 102, 1))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+>All : Symbol(All, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 45))
+
+    switch (true) {
+        case input.kind === "A":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+        case input.kind === "B":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+            if (input.kind === "A") {
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10))
+
+                return;
+            }
+
+            input; // Should be B;
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+
+            //  ^?
+
+            // fallthrough
+        default:
+            input; // Should be B | D | E
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+
+            //  ^?
+            break;
+
+        case input.kind === "C":
+>input.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 0, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 1, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 2, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 3, 10), Decl(narrowByClauseExpressionInSwitchTrue5.ts, 4, 10))
+
+            input; // Should be C
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+
+            //  ^?
+            break;
+    }
+
+    input; // Should not be A
+>input : Symbol(input, Decl(narrowByClauseExpressionInSwitchTrue5.ts, 104, 19))
+
+    //  ^?
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue5.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue5.types
new file mode 100644
index 0000000000000..d2b4c5c0780de
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue5.types
@@ -0,0 +1,348 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue5.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue5.ts ===
+type A = { kind: "A", value: number };
+>A : { kind: "A"; value: number; }
+>kind : "A"
+>value : number
+
+type B = { kind: "B", name: string };
+>B : { kind: "B"; name: string; }
+>kind : "B"
+>name : string
+
+type C = { kind: "C", cond: boolean };
+>C : { kind: "C"; cond: boolean; }
+>kind : "C"
+>cond : boolean
+
+type D = { kind: "D", value: boolean };
+>D : { kind: "D"; value: boolean; }
+>kind : "D"
+>value : boolean
+
+type E = { kind: "E", x: number, y: number };
+>E : { kind: "E"; x: number; y: number; }
+>kind : "E"
+>x : number
+>y : number
+
+type All = A | B | C | D | E;
+>All : A | B | C | D | E
+
+function fn1switch(input: All) {
+>fn1switch : (input: All) => void
+>input : All
+
+    switch (true) {
+>true : true
+
+        case input.kind === "A":
+>input.kind === "A" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"A" : "A"
+
+        case input.kind === "B":
+>input.kind === "B" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"B" : "B"
+
+            if (input.kind === "A") {
+>input.kind === "A" : boolean
+>input.kind : "A" | "B"
+>input : A | B
+>kind : "A" | "B"
+>"A" : "A"
+
+                return;
+            }
+
+            input; // Should be B;
+>input : B
+
+            //  ^?
+
+            // fallthrough
+        case input.kind === "C":
+>input.kind === "C" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"C" : "C"
+
+            input; // Should be B | C
+>input : B | C
+
+            //  ^?
+            break;
+        default:
+            input; // Should be D | E
+>input : D | E
+
+            //  ^?
+    }
+
+    input; // Should not be A
+>input : B | C | D | E
+
+    //  ^?
+}
+
+function fn1ifelse(input: All) {
+>fn1ifelse : (input: All) => void
+>input : All
+
+    if (input.kind === "A" || input.kind === "B") {
+>input.kind === "A" || input.kind === "B" : boolean
+>input.kind === "A" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"A" : "A"
+>input.kind === "B" : boolean
+>input.kind : "B" | "C" | "D" | "E"
+>input : B | C | D | E
+>kind : "B" | "C" | "D" | "E"
+>"B" : "B"
+
+        if (input.kind === "A") {
+>input.kind === "A" : boolean
+>input.kind : "A" | "B"
+>input : A | B
+>kind : "A" | "B"
+>"A" : "A"
+
+            return;
+        }
+
+        input; // Should be B;
+>input : B
+
+        //  ^?
+    }
+    if (input.kind === "C" || input.kind === "B") {
+>input.kind === "C" || input.kind === "B" : boolean
+>input.kind === "C" : boolean
+>input.kind : "B" | "C" | "D" | "E"
+>input : B | C | D | E
+>kind : "B" | "C" | "D" | "E"
+>"C" : "C"
+>input.kind === "B" : boolean
+>input.kind : "B" | "D" | "E"
+>input : B | D | E
+>kind : "B" | "D" | "E"
+>"B" : "B"
+
+        input; // Should be B | C
+>input : B | C
+
+        //  ^?
+    }
+    else {
+        input; // Should be D | E
+>input : D | E
+
+        //  ^?
+    }
+
+    input; // Should not be A
+>input : B | C | D | E
+
+    //  ^?
+}
+
+function fn2switch(input: All) {
+>fn2switch : (input: All) => void
+>input : All
+
+    switch (true) {
+>true : true
+
+        case input.kind === "A":
+>input.kind === "A" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"A" : "A"
+
+        case input.kind === "B":
+>input.kind === "B" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"B" : "B"
+
+            if (input.kind === "A") {
+>input.kind === "A" : boolean
+>input.kind : "A" | "B"
+>input : A | B
+>kind : "A" | "B"
+>"A" : "A"
+
+                return;
+            }
+
+            input; // Should be B;
+>input : B
+
+            //  ^?
+
+            // fallthrough
+        case input.kind === "C":
+>input.kind === "C" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"C" : "C"
+
+            input; // Should be B | C
+>input : B | C
+
+            //  ^?
+            break;
+        default:
+            input; // Should be D | E
+>input : D | E
+
+            //  ^?
+            return;
+    }
+
+    input; // Should be B | C
+>input : B | C
+
+    //  ^?
+}
+
+function fn2ifelse(input: All) {
+>fn2ifelse : (input: All) => void
+>input : All
+
+    if (input.kind === "A" || input.kind === "B") {
+>input.kind === "A" || input.kind === "B" : boolean
+>input.kind === "A" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"A" : "A"
+>input.kind === "B" : boolean
+>input.kind : "B" | "C" | "D" | "E"
+>input : B | C | D | E
+>kind : "B" | "C" | "D" | "E"
+>"B" : "B"
+
+        if (input.kind === "A") {
+>input.kind === "A" : boolean
+>input.kind : "A" | "B"
+>input : A | B
+>kind : "A" | "B"
+>"A" : "A"
+
+            return;
+        }
+
+        input; // Should be B;
+>input : B
+
+        //  ^?
+    }
+    if (input.kind === "C" || input.kind === "B") {
+>input.kind === "C" || input.kind === "B" : boolean
+>input.kind === "C" : boolean
+>input.kind : "B" | "C" | "D" | "E"
+>input : B | C | D | E
+>kind : "B" | "C" | "D" | "E"
+>"C" : "C"
+>input.kind === "B" : boolean
+>input.kind : "B" | "D" | "E"
+>input : B | D | E
+>kind : "B" | "D" | "E"
+>"B" : "B"
+
+        input; // Should be B | C
+>input : B | C
+
+        //  ^?
+    }
+    else {
+        input; // Should be D | E
+>input : D | E
+
+        //  ^?
+        return;
+    }
+
+    input; // Should be B | C
+>input : B | C
+
+    //  ^?
+}
+
+function fn3switch(input: All) {
+>fn3switch : (input: All) => void
+>input : All
+
+    switch (true) {
+>true : true
+
+        case input.kind === "A":
+>input.kind === "A" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"A" : "A"
+
+        case input.kind === "B":
+>input.kind === "B" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"B" : "B"
+
+            if (input.kind === "A") {
+>input.kind === "A" : boolean
+>input.kind : "A" | "B"
+>input : A | B
+>kind : "A" | "B"
+>"A" : "A"
+
+                return;
+            }
+
+            input; // Should be B;
+>input : B
+
+            //  ^?
+
+            // fallthrough
+        default:
+            input; // Should be B | D | E
+>input : B | D | E
+
+            //  ^?
+            break;
+
+        case input.kind === "C":
+>input.kind === "C" : boolean
+>input.kind : "A" | "B" | "C" | "D" | "E"
+>input : All
+>kind : "A" | "B" | "C" | "D" | "E"
+>"C" : "C"
+
+            input; // Should be C
+>input : C
+
+            //  ^?
+            break;
+    }
+
+    input; // Should not be A
+>input : B | C | D | E
+
+    //  ^?
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.errors.txt b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.errors.txt
new file mode 100644
index 0000000000000..e33e6ac6fceab
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.errors.txt
@@ -0,0 +1,89 @@
+narrowByClauseExpressionInSwitchTrue6.ts(70,15): error TS2339: Property 'bProps' does not exist on type 'A | B'.
+  Property 'bProps' does not exist on type 'A'.
+narrowByClauseExpressionInSwitchTrue6.ts(73,15): error TS2339: Property 'cProps' does not exist on type 'MyType'.
+  Property 'cProps' does not exist on type 'A'.
+
+
+==== narrowByClauseExpressionInSwitchTrue6.ts (2 errors) ====
+    interface A {
+        kind: "a";
+        aProps: string;
+    }
+    
+    interface B {
+        kind: "b";
+        bProps: string;
+    }
+    
+    interface C {
+        kind: "c";
+        cProps: string;
+    }
+    
+    
+    type MyType = A | B | C;
+    
+    function isA(x: MyType) {
+        switch (true) {
+            default:
+                const never: never = x;
+            case x.kind === "a":
+                x.aProps;
+                break;
+            case x.kind === "b":
+                x.bProps;
+                break;
+            case x.kind === "c":
+                x.cProps;
+                break;
+        }
+    
+        switch (true) {
+            default:
+                const never: never = x;
+            case x.kind === "a": {
+                x.aProps;
+                break;
+            }
+            case x.kind === "b": {
+                x.bProps;
+                break;
+            }
+            case x.kind === "c": {
+                x.cProps;
+                break;
+            }
+        }
+        
+        switch (true) {
+            default:
+                x.aProps;
+                break;
+            case x.kind === "b":
+                x.bProps;
+                break;
+            case x.kind === "c":
+                x.cProps;
+                break;
+        }
+    
+        switch (true) {
+            default:
+                const never: never = x;
+            case x.kind === "a":
+                x.aProps;
+                // fallthrough
+            case x.kind === "b":
+                x.bProps;
+                  ~~~~~~
+!!! error TS2339: Property 'bProps' does not exist on type 'A | B'.
+!!! error TS2339:   Property 'bProps' does not exist on type 'A'.
+                // fallthrough
+            case x.kind === "c":
+                x.cProps;
+                  ~~~~~~
+!!! error TS2339: Property 'cProps' does not exist on type 'MyType'.
+!!! error TS2339:   Property 'cProps' does not exist on type 'A'.
+        }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.symbols
new file mode 100644
index 0000000000000..9ed6be6a7cf6c
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.symbols
@@ -0,0 +1,198 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue6.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue6.ts ===
+interface A {
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 0))
+
+    kind: "a";
+>kind : Symbol(A.kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13))
+
+    aProps: string;
+>aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+}
+
+interface B {
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 3, 1))
+
+    kind: "b";
+>kind : Symbol(B.kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13))
+
+    bProps: string;
+>bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+}
+
+interface C {
+>C : Symbol(C, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 8, 1))
+
+    kind: "c";
+>kind : Symbol(C.kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+    cProps: string;
+>cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+}
+
+
+type MyType = A | B | C;
+>MyType : Symbol(MyType, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 13, 1))
+>A : Symbol(A, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 0))
+>B : Symbol(B, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 3, 1))
+>C : Symbol(C, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 8, 1))
+
+function isA(x: MyType) {
+>isA : Symbol(isA, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 16, 24))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>MyType : Symbol(MyType, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 13, 1))
+
+    switch (true) {
+        default:
+            const never: never = x;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 21, 17))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+
+        case x.kind === "a":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.aProps;
+>x.aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+
+            break;
+        case x.kind === "b":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.bProps;
+>x.bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+
+            break;
+        case x.kind === "c":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.cProps;
+>x.cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+
+            break;
+    }
+
+    switch (true) {
+        default:
+            const never: never = x;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 35, 17))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+
+        case x.kind === "a": {
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.aProps;
+>x.aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+
+            break;
+        }
+        case x.kind === "b": {
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.bProps;
+>x.bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+
+            break;
+        }
+        case x.kind === "c": {
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.cProps;
+>x.cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+
+            break;
+        }
+    }
+    
+    switch (true) {
+        default:
+            x.aProps;
+>x.aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+
+            break;
+        case x.kind === "b":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.bProps;
+>x.bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>bProps : Symbol(B.bProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 6, 14))
+
+            break;
+        case x.kind === "c":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.cProps;
+>x.cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>cProps : Symbol(C.cProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 11, 14))
+
+            break;
+    }
+
+    switch (true) {
+        default:
+            const never: never = x;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 64, 17))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+
+        case x.kind === "a":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.aProps;
+>x.aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>aProps : Symbol(A.aProps, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 1, 14))
+
+            // fallthrough
+        case x.kind === "b":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.bProps;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+
+            // fallthrough
+        case x.kind === "c":
+>x.kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+>kind : Symbol(kind, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 0, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 5, 13), Decl(narrowByClauseExpressionInSwitchTrue6.ts, 10, 13))
+
+            x.cProps;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue6.ts, 18, 13))
+    }
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.types
new file mode 100644
index 0000000000000..4a96c67b07136
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue6.types
@@ -0,0 +1,222 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue6.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue6.ts ===
+interface A {
+    kind: "a";
+>kind : "a"
+
+    aProps: string;
+>aProps : string
+}
+
+interface B {
+    kind: "b";
+>kind : "b"
+
+    bProps: string;
+>bProps : string
+}
+
+interface C {
+    kind: "c";
+>kind : "c"
+
+    cProps: string;
+>cProps : string
+}
+
+
+type MyType = A | B | C;
+>MyType : A | B | C
+
+function isA(x: MyType) {
+>isA : (x: MyType) => void
+>x : MyType
+
+    switch (true) {
+>true : true
+
+        default:
+            const never: never = x;
+>never : never
+>x : never
+
+        case x.kind === "a":
+>x.kind === "a" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"a" : "a"
+
+            x.aProps;
+>x.aProps : string
+>x : A
+>aProps : string
+
+            break;
+        case x.kind === "b":
+>x.kind === "b" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"b" : "b"
+
+            x.bProps;
+>x.bProps : string
+>x : B
+>bProps : string
+
+            break;
+        case x.kind === "c":
+>x.kind === "c" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"c" : "c"
+
+            x.cProps;
+>x.cProps : string
+>x : C
+>cProps : string
+
+            break;
+    }
+
+    switch (true) {
+>true : true
+
+        default:
+            const never: never = x;
+>never : never
+>x : never
+
+        case x.kind === "a": {
+>x.kind === "a" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"a" : "a"
+
+            x.aProps;
+>x.aProps : string
+>x : A
+>aProps : string
+
+            break;
+        }
+        case x.kind === "b": {
+>x.kind === "b" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"b" : "b"
+
+            x.bProps;
+>x.bProps : string
+>x : B
+>bProps : string
+
+            break;
+        }
+        case x.kind === "c": {
+>x.kind === "c" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"c" : "c"
+
+            x.cProps;
+>x.cProps : string
+>x : C
+>cProps : string
+
+            break;
+        }
+    }
+    
+    switch (true) {
+>true : true
+
+        default:
+            x.aProps;
+>x.aProps : string
+>x : A
+>aProps : string
+
+            break;
+        case x.kind === "b":
+>x.kind === "b" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"b" : "b"
+
+            x.bProps;
+>x.bProps : string
+>x : B
+>bProps : string
+
+            break;
+        case x.kind === "c":
+>x.kind === "c" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"c" : "c"
+
+            x.cProps;
+>x.cProps : string
+>x : C
+>cProps : string
+
+            break;
+    }
+
+    switch (true) {
+>true : true
+
+        default:
+            const never: never = x;
+>never : never
+>x : never
+
+        case x.kind === "a":
+>x.kind === "a" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"a" : "a"
+
+            x.aProps;
+>x.aProps : string
+>x : A
+>aProps : string
+
+            // fallthrough
+        case x.kind === "b":
+>x.kind === "b" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"b" : "b"
+
+            x.bProps;
+>x.bProps : any
+>x : A | B
+>bProps : any
+
+            // fallthrough
+        case x.kind === "c":
+>x.kind === "c" : boolean
+>x.kind : "a" | "b" | "c"
+>x : MyType
+>kind : "a" | "b" | "c"
+>"c" : "c"
+
+            x.cProps;
+>x.cProps : any
+>x : MyType
+>cProps : any
+    }
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.errors.txt b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.errors.txt
new file mode 100644
index 0000000000000..ae09d39b7ca88
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.errors.txt
@@ -0,0 +1,90 @@
+narrowByClauseExpressionInSwitchTrue7.ts(80,19): error TS2322: Type 'Derived2' is not assignable to type 'never'.
+
+
+==== narrowByClauseExpressionInSwitchTrue7.ts (1 errors) ====
+    class Base {
+        basey: string = "";
+    }
+    
+    class Derived1 extends Base {
+        d: string = "";
+    }
+    
+    class Derived2 extends Base {
+        d: string = "";
+        other: string = "";
+    }
+    
+    function classy(base: Base, someDerived: Derived1 | Derived2) {
+        switch (true) {
+            case base instanceof Derived1:
+                base.d
+                // fallthrough
+            default:
+                base.basey
+        }
+    
+        switch (true) {
+            case someDerived instanceof Derived1:
+                someDerived.d
+                break;
+            case someDerived instanceof Derived2:
+                someDerived.d
+                break
+            default:
+                const never: never = someDerived;
+        }
+    
+        switch (true) {
+            case someDerived instanceof Derived1:
+                someDerived.d
+                // fallthrough
+            case someDerived instanceof Derived2:
+                someDerived.d
+                break
+            default:
+                const never: never = someDerived;
+        }
+    
+        switch (true) {
+            default:
+                const never: never = someDerived;
+            case someDerived instanceof Derived1:
+                someDerived.d;
+                someDerived.basey;
+                break
+            case someDerived instanceof Derived2:
+                someDerived.d;
+                someDerived.other;
+        }
+    
+        switch (true) {
+            case someDerived instanceof Derived1:
+                someDerived.d;
+                someDerived.basey;
+                break
+            default:
+                const never: never = someDerived;
+            case someDerived instanceof Derived2:
+                someDerived.d;
+                someDerived.other;
+        }
+    
+        switch (true) {
+            case someDerived instanceof Derived1:
+                someDerived.d;
+                someDerived.basey;
+                break
+            case someDerived instanceof Derived2:
+                someDerived.d;
+                someDerived.other;
+            default:
+                someDerived.d;
+                someDerived.other;
+                const never: never = someDerived;
+                      ~~~~~
+!!! error TS2322: Type 'Derived2' is not assignable to type 'never'.
+        }
+    
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.symbols
new file mode 100644
index 0000000000000..ad0dd8f89d894
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.symbols
@@ -0,0 +1,229 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue7.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue7.ts ===
+class Base {
+>Base : Symbol(Base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 0))
+
+    basey: string = "";
+>basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+}
+
+class Derived1 extends Base {
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+>Base : Symbol(Base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 0))
+
+    d: string = "";
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+}
+
+class Derived2 extends Base {
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+>Base : Symbol(Base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 0))
+
+    d: string = "";
+>d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+    other: string = "";
+>other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+}
+
+function classy(base: Base, someDerived: Derived1 | Derived2) {
+>classy : Symbol(classy, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 11, 1))
+>base : Symbol(base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 16))
+>Base : Symbol(Base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 0))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+
+    switch (true) {
+        case base instanceof Derived1:
+>base : Symbol(base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 16))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+
+            base.d
+>base.d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+>base : Symbol(base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 16))
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+
+            // fallthrough
+        default:
+            base.basey
+>base.basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+>base : Symbol(base, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 16))
+>basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+
+            someDerived.d
+>someDerived.d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+
+            break;
+        case someDerived instanceof Derived2:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+
+            someDerived.d
+>someDerived.d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+            break
+        default:
+            const never: never = someDerived;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 30, 17))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+
+            someDerived.d
+>someDerived.d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+
+            // fallthrough
+        case someDerived instanceof Derived2:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+
+            someDerived.d
+>someDerived.d : Symbol(d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29), Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29), Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+            break
+        default:
+            const never: never = someDerived;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 41, 17))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+    }
+
+    switch (true) {
+        default:
+            const never: never = someDerived;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 46, 17))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+
+        case someDerived instanceof Derived1:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+
+            someDerived.d;
+>someDerived.d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+
+            someDerived.basey;
+>someDerived.basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+
+            break
+        case someDerived instanceof Derived2:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+
+            someDerived.d;
+>someDerived.d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+            someDerived.other;
+>someDerived.other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+
+            someDerived.d;
+>someDerived.d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+
+            someDerived.basey;
+>someDerived.basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+
+            break
+        default:
+            const never: never = someDerived;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 62, 17))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+
+        case someDerived instanceof Derived2:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+
+            someDerived.d;
+>someDerived.d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+            someDerived.other;
+>someDerived.other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived1 : Symbol(Derived1, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 2, 1))
+
+            someDerived.d;
+>someDerived.d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived1.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 4, 29))
+
+            someDerived.basey;
+>someDerived.basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>basey : Symbol(Base.basey, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 0, 12))
+
+            break
+        case someDerived instanceof Derived2:
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>Derived2 : Symbol(Derived2, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 6, 1))
+
+            someDerived.d;
+>someDerived.d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+            someDerived.other;
+>someDerived.other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+
+        default:
+            someDerived.d;
+>someDerived.d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>d : Symbol(Derived2.d, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 8, 29))
+
+            someDerived.other;
+>someDerived.other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+>other : Symbol(Derived2.other, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 9, 19))
+
+            const never: never = someDerived;
+>never : Symbol(never, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 79, 17))
+>someDerived : Symbol(someDerived, Decl(narrowByClauseExpressionInSwitchTrue7.ts, 13, 27))
+    }
+
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.types
new file mode 100644
index 0000000000000..a783c583b22f3
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue7.types
@@ -0,0 +1,253 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue7.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue7.ts ===
+class Base {
+>Base : Base
+
+    basey: string = "";
+>basey : string
+>"" : ""
+}
+
+class Derived1 extends Base {
+>Derived1 : Derived1
+>Base : Base
+
+    d: string = "";
+>d : string
+>"" : ""
+}
+
+class Derived2 extends Base {
+>Derived2 : Derived2
+>Base : Base
+
+    d: string = "";
+>d : string
+>"" : ""
+
+    other: string = "";
+>other : string
+>"" : ""
+}
+
+function classy(base: Base, someDerived: Derived1 | Derived2) {
+>classy : (base: Base, someDerived: Derived1 | Derived2) => void
+>base : Base
+>someDerived : Derived1 | Derived2
+
+    switch (true) {
+>true : true
+
+        case base instanceof Derived1:
+>base instanceof Derived1 : boolean
+>base : Base
+>Derived1 : typeof Derived1
+
+            base.d
+>base.d : string
+>base : Derived1
+>d : string
+
+            // fallthrough
+        default:
+            base.basey
+>base.basey : string
+>base : Base
+>basey : string
+    }
+
+    switch (true) {
+>true : true
+
+        case someDerived instanceof Derived1:
+>someDerived instanceof Derived1 : boolean
+>someDerived : Derived1 | Derived2
+>Derived1 : typeof Derived1
+
+            someDerived.d
+>someDerived.d : string
+>someDerived : Derived1
+>d : string
+
+            break;
+        case someDerived instanceof Derived2:
+>someDerived instanceof Derived2 : boolean
+>someDerived : Derived1 | Derived2
+>Derived2 : typeof Derived2
+
+            someDerived.d
+>someDerived.d : string
+>someDerived : Derived2
+>d : string
+
+            break
+        default:
+            const never: never = someDerived;
+>never : never
+>someDerived : never
+    }
+
+    switch (true) {
+>true : true
+
+        case someDerived instanceof Derived1:
+>someDerived instanceof Derived1 : boolean
+>someDerived : Derived1 | Derived2
+>Derived1 : typeof Derived1
+
+            someDerived.d
+>someDerived.d : string
+>someDerived : Derived1
+>d : string
+
+            // fallthrough
+        case someDerived instanceof Derived2:
+>someDerived instanceof Derived2 : boolean
+>someDerived : Derived1 | Derived2
+>Derived2 : typeof Derived2
+
+            someDerived.d
+>someDerived.d : string
+>someDerived : Derived1 | Derived2
+>d : string
+
+            break
+        default:
+            const never: never = someDerived;
+>never : never
+>someDerived : never
+    }
+
+    switch (true) {
+>true : true
+
+        default:
+            const never: never = someDerived;
+>never : never
+>someDerived : never
+
+        case someDerived instanceof Derived1:
+>someDerived instanceof Derived1 : boolean
+>someDerived : Derived1 | Derived2
+>Derived1 : typeof Derived1
+
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived1
+>d : string
+
+            someDerived.basey;
+>someDerived.basey : string
+>someDerived : Derived1
+>basey : string
+
+            break
+        case someDerived instanceof Derived2:
+>someDerived instanceof Derived2 : boolean
+>someDerived : Derived1 | Derived2
+>Derived2 : typeof Derived2
+
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived2
+>d : string
+
+            someDerived.other;
+>someDerived.other : string
+>someDerived : Derived2
+>other : string
+    }
+
+    switch (true) {
+>true : true
+
+        case someDerived instanceof Derived1:
+>someDerived instanceof Derived1 : boolean
+>someDerived : Derived1 | Derived2
+>Derived1 : typeof Derived1
+
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived1
+>d : string
+
+            someDerived.basey;
+>someDerived.basey : string
+>someDerived : Derived1
+>basey : string
+
+            break
+        default:
+            const never: never = someDerived;
+>never : never
+>someDerived : never
+
+        case someDerived instanceof Derived2:
+>someDerived instanceof Derived2 : boolean
+>someDerived : Derived1 | Derived2
+>Derived2 : typeof Derived2
+
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived2
+>d : string
+
+            someDerived.other;
+>someDerived.other : string
+>someDerived : Derived2
+>other : string
+    }
+
+    switch (true) {
+>true : true
+
+        case someDerived instanceof Derived1:
+>someDerived instanceof Derived1 : boolean
+>someDerived : Derived1 | Derived2
+>Derived1 : typeof Derived1
+
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived1
+>d : string
+
+            someDerived.basey;
+>someDerived.basey : string
+>someDerived : Derived1
+>basey : string
+
+            break
+        case someDerived instanceof Derived2:
+>someDerived instanceof Derived2 : boolean
+>someDerived : Derived1 | Derived2
+>Derived2 : typeof Derived2
+
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived2
+>d : string
+
+            someDerived.other;
+>someDerived.other : string
+>someDerived : Derived2
+>other : string
+
+        default:
+            someDerived.d;
+>someDerived.d : string
+>someDerived : Derived2
+>d : string
+
+            someDerived.other;
+>someDerived.other : string
+>someDerived : Derived2
+>other : string
+
+            const never: never = someDerived;
+>never : never
+>someDerived : Derived2
+    }
+
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue8.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue8.symbols
new file mode 100644
index 0000000000000..ec14234e62b6c
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue8.symbols
@@ -0,0 +1,57 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue8.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue8.ts ===
+function foo(cond1: boolean, cond2: boolean) {
+>foo : Symbol(foo, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 0))
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 13))
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 28))
+
+    switch (true) {
+        case cond1:
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 13))
+
+            cond1; // Should be true
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 13))
+
+            //  ^?
+            cond2; // Should be boolean
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 28))
+
+            //  ^?
+            break;
+
+        case cond2:
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 28))
+
+            cond1; // Should be false?
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 13))
+
+            //  ^?
+            cond2; // Should be true
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 28))
+
+            //  ^?
+            break;
+
+        default:
+            cond1; // Should be false?
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 13))
+
+            //  ^?
+            cond2; // Should be false?
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 28))
+
+            //  ^?
+            break;
+    }
+
+    cond1; // Should be boolean
+>cond1 : Symbol(cond1, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 13))
+
+    //  ^?
+    cond2; // Should be boolean
+>cond2 : Symbol(cond2, Decl(narrowByClauseExpressionInSwitchTrue8.ts, 0, 28))
+
+    //  ^?
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue8.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue8.types
new file mode 100644
index 0000000000000..45230dc5e12b9
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue8.types
@@ -0,0 +1,59 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue8.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue8.ts ===
+function foo(cond1: boolean, cond2: boolean) {
+>foo : (cond1: boolean, cond2: boolean) => void
+>cond1 : boolean
+>cond2 : boolean
+
+    switch (true) {
+>true : true
+
+        case cond1:
+>cond1 : boolean
+
+            cond1; // Should be true
+>cond1 : true
+
+            //  ^?
+            cond2; // Should be boolean
+>cond2 : boolean
+
+            //  ^?
+            break;
+
+        case cond2:
+>cond2 : boolean
+
+            cond1; // Should be false?
+>cond1 : false
+
+            //  ^?
+            cond2; // Should be true
+>cond2 : true
+
+            //  ^?
+            break;
+
+        default:
+            cond1; // Should be false?
+>cond1 : false
+
+            //  ^?
+            cond2; // Should be false?
+>cond2 : false
+
+            //  ^?
+            break;
+    }
+
+    cond1; // Should be boolean
+>cond1 : boolean
+
+    //  ^?
+    cond2; // Should be boolean
+>cond2 : boolean
+
+    //  ^?
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue9.symbols b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue9.symbols
new file mode 100644
index 0000000000000..1cbdfc55b276d
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue9.symbols
@@ -0,0 +1,40 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue9.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue9.ts ===
+interface IProps {
+>IProps : Symbol(IProps, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 0, 0))
+
+    one: boolean;
+>one : Symbol(IProps.one, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 0, 18))
+}
+
+class Foo {
+>Foo : Symbol(Foo, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 2, 1))
+
+    mine: string = "";
+>mine : Symbol(Foo.mine, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 4, 11))
+
+    myMethod(x: IProps) {
+>myMethod : Symbol(Foo.myMethod, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 5, 22))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 7, 13))
+>IProps : Symbol(IProps, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 0, 0))
+
+        const { one } = x;
+>one : Symbol(one, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 8, 15))
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 7, 13))
+
+        switch (true) {
+            case one:
+>one : Symbol(one, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 8, 15))
+
+                break;
+            default:
+                let x = this.mine;
+>x : Symbol(x, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 13, 19))
+>this.mine : Symbol(Foo.mine, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 4, 11))
+>this : Symbol(Foo, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 2, 1))
+>mine : Symbol(Foo.mine, Decl(narrowByClauseExpressionInSwitchTrue9.ts, 4, 11))
+        }
+    }
+}
+
diff --git a/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue9.types b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue9.types
new file mode 100644
index 0000000000000..75557462a5b20
--- /dev/null
+++ b/tests/baselines/reference/narrowByClauseExpressionInSwitchTrue9.types
@@ -0,0 +1,40 @@
+//// [tests/cases/compiler/narrowByClauseExpressionInSwitchTrue9.ts] ////
+
+=== narrowByClauseExpressionInSwitchTrue9.ts ===
+interface IProps {
+    one: boolean;
+>one : boolean
+}
+
+class Foo {
+>Foo : Foo
+
+    mine: string = "";
+>mine : string
+>"" : ""
+
+    myMethod(x: IProps) {
+>myMethod : (x: IProps) => void
+>x : IProps
+
+        const { one } = x;
+>one : boolean
+>x : IProps
+
+        switch (true) {
+>true : true
+
+            case one:
+>one : boolean
+
+                break;
+            default:
+                let x = this.mine;
+>x : string
+>this.mine : string
+>this : this
+>mine : string
+        }
+    }
+}
+
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue1.ts
similarity index 100%
rename from tests/cases/compiler/narrowByClauseExpressionInSwitchTrue.ts
rename to tests/cases/compiler/narrowByClauseExpressionInSwitchTrue1.ts
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue10.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue10.ts
new file mode 100644
index 0000000000000..7d48369ca34e0
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue10.ts
@@ -0,0 +1,56 @@
+// @strict: true
+// @noEmit: true
+
+function foo(cond1: boolean, cond2: boolean) {
+    switch (true) {
+        case cond1 || cond2:
+            cond1; // boolean
+            //  ^?
+            cond2; // boolean
+            //  ^?
+            break;
+
+        case cond2:
+            cond1; // false
+            //  ^?
+            cond2;; // never
+            //  ^?
+            break;
+
+        default:
+            cond1; // false
+            //  ^?
+            cond2; // false
+            //  ^?
+            break;
+    }
+
+    cond1; // boolean
+    //  ^?
+    cond2; // boolean
+    //  ^?
+}
+
+function blah(cond1: boolean, cond2: boolean) {
+    if (cond1 || cond2) {
+        cond1; // boolean
+        //  ^?
+        cond2; // boolean
+        //  ^?
+    } else if (cond2) {
+        cond1; // false
+        //  ^?
+        cond2; // never
+        //  ^?
+    } else {
+        cond1; // false
+        //  ^?
+        cond2; // false
+        //  ^?
+    }
+
+    cond1; // boolean
+    //  ^?
+    cond2; // boolean
+    //  ^?
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue2.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue2.ts
new file mode 100644
index 0000000000000..461e3505c393a
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue2.ts
@@ -0,0 +1,29 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/TypeScript/issues/55986
+
+declare const f: 'a' | 'b' | 'c';
+
+switch(true) {
+    case f === 'a':
+    case f === 'b':
+        f;
+        break
+    default:
+        f;
+}
+
+f;
+
+switch(true) {
+    case f === 'a':
+        f;
+    case f === 'b':
+        f;
+        break
+    default:
+        f;
+}
+
+f;
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue3.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue3.ts
new file mode 100644
index 0000000000000..d0dbafccbb108
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue3.ts
@@ -0,0 +1,22 @@
+// @strict: true
+// @noEmit: true
+
+type Shape =
+    | { kind: "circle", radius: number }
+    | { kind: "square", sideLength: number }
+
+function wat(shape: Shape) {
+    switch (true) {
+        case shape.kind === "circle":
+            return Math.PI * shape.radius ** 2;
+        case shape.kind === "circle": // should error
+    }
+
+    if (shape.kind === "circle") {
+        return Math.PI * shape.radius ** 2;
+    }
+    else if (shape.kind === "circle") {
+        //         ~~~~
+        // Property 'kind' does not exist on type 'never'.
+    }
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue4.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue4.ts
new file mode 100644
index 0000000000000..15596fd7ad11a
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue4.ts
@@ -0,0 +1,12 @@
+// @strict: true
+// @noEmit: true
+
+declare const f: 'a' | 'b' | 'c';
+
+switch (true) {
+  case f === "a":
+  default:
+    f;
+  case f === "b":
+    f;
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue5.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue5.ts
new file mode 100644
index 0000000000000..f4aee3ff151e1
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue5.ts
@@ -0,0 +1,133 @@
+// @strict: true
+// @noEmit: true
+
+type A = { kind: "A", value: number };
+type B = { kind: "B", name: string };
+type C = { kind: "C", cond: boolean };
+type D = { kind: "D", value: boolean };
+type E = { kind: "E", x: number, y: number };
+
+type All = A | B | C | D | E;
+
+function fn1switch(input: All) {
+    switch (true) {
+        case input.kind === "A":
+        case input.kind === "B":
+            if (input.kind === "A") {
+                return;
+            }
+
+            input; // Should be B;
+            //  ^?
+
+            // fallthrough
+        case input.kind === "C":
+            input; // Should be B | C
+            //  ^?
+            break;
+        default:
+            input; // Should be D | E
+            //  ^?
+    }
+
+    input; // Should not be A
+    //  ^?
+}
+
+function fn1ifelse(input: All) {
+    if (input.kind === "A" || input.kind === "B") {
+        if (input.kind === "A") {
+            return;
+        }
+
+        input; // Should be B;
+        //  ^?
+    }
+    if (input.kind === "C" || input.kind === "B") {
+        input; // Should be B | C
+        //  ^?
+    }
+    else {
+        input; // Should be D | E
+        //  ^?
+    }
+
+    input; // Should not be A
+    //  ^?
+}
+
+function fn2switch(input: All) {
+    switch (true) {
+        case input.kind === "A":
+        case input.kind === "B":
+            if (input.kind === "A") {
+                return;
+            }
+
+            input; // Should be B;
+            //  ^?
+
+            // fallthrough
+        case input.kind === "C":
+            input; // Should be B | C
+            //  ^?
+            break;
+        default:
+            input; // Should be D | E
+            //  ^?
+            return;
+    }
+
+    input; // Should be B | C
+    //  ^?
+}
+
+function fn2ifelse(input: All) {
+    if (input.kind === "A" || input.kind === "B") {
+        if (input.kind === "A") {
+            return;
+        }
+
+        input; // Should be B;
+        //  ^?
+    }
+    if (input.kind === "C" || input.kind === "B") {
+        input; // Should be B | C
+        //  ^?
+    }
+    else {
+        input; // Should be D | E
+        //  ^?
+        return;
+    }
+
+    input; // Should be B | C
+    //  ^?
+}
+
+function fn3switch(input: All) {
+    switch (true) {
+        case input.kind === "A":
+        case input.kind === "B":
+            if (input.kind === "A") {
+                return;
+            }
+
+            input; // Should be B;
+            //  ^?
+
+            // fallthrough
+        default:
+            input; // Should be B | D | E
+            //  ^?
+            break;
+
+        case input.kind === "C":
+            input; // Should be C
+            //  ^?
+            break;
+    }
+
+    input; // Should not be A
+    //  ^?
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue6.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue6.ts
new file mode 100644
index 0000000000000..491355b79e906
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue6.ts
@@ -0,0 +1,78 @@
+// @strict: true
+// @noEmit: true
+
+interface A {
+    kind: "a";
+    aProps: string;
+}
+
+interface B {
+    kind: "b";
+    bProps: string;
+}
+
+interface C {
+    kind: "c";
+    cProps: string;
+}
+
+
+type MyType = A | B | C;
+
+function isA(x: MyType) {
+    switch (true) {
+        default:
+            const never: never = x;
+        case x.kind === "a":
+            x.aProps;
+            break;
+        case x.kind === "b":
+            x.bProps;
+            break;
+        case x.kind === "c":
+            x.cProps;
+            break;
+    }
+
+    switch (true) {
+        default:
+            const never: never = x;
+        case x.kind === "a": {
+            x.aProps;
+            break;
+        }
+        case x.kind === "b": {
+            x.bProps;
+            break;
+        }
+        case x.kind === "c": {
+            x.cProps;
+            break;
+        }
+    }
+    
+    switch (true) {
+        default:
+            x.aProps;
+            break;
+        case x.kind === "b":
+            x.bProps;
+            break;
+        case x.kind === "c":
+            x.cProps;
+            break;
+    }
+
+    switch (true) {
+        default:
+            const never: never = x;
+        case x.kind === "a":
+            x.aProps;
+            // fallthrough
+        case x.kind === "b":
+            x.bProps;
+            // fallthrough
+        case x.kind === "c":
+            x.cProps;
+    }
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue7.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue7.ts
new file mode 100644
index 0000000000000..d482d8fa033a4
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue7.ts
@@ -0,0 +1,86 @@
+// @strict: true
+// @noEmit: true
+
+class Base {
+    basey: string = "";
+}
+
+class Derived1 extends Base {
+    d: string = "";
+}
+
+class Derived2 extends Base {
+    d: string = "";
+    other: string = "";
+}
+
+function classy(base: Base, someDerived: Derived1 | Derived2) {
+    switch (true) {
+        case base instanceof Derived1:
+            base.d
+            // fallthrough
+        default:
+            base.basey
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+            someDerived.d
+            break;
+        case someDerived instanceof Derived2:
+            someDerived.d
+            break
+        default:
+            const never: never = someDerived;
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+            someDerived.d
+            // fallthrough
+        case someDerived instanceof Derived2:
+            someDerived.d
+            break
+        default:
+            const never: never = someDerived;
+    }
+
+    switch (true) {
+        default:
+            const never: never = someDerived;
+        case someDerived instanceof Derived1:
+            someDerived.d;
+            someDerived.basey;
+            break
+        case someDerived instanceof Derived2:
+            someDerived.d;
+            someDerived.other;
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+            someDerived.d;
+            someDerived.basey;
+            break
+        default:
+            const never: never = someDerived;
+        case someDerived instanceof Derived2:
+            someDerived.d;
+            someDerived.other;
+    }
+
+    switch (true) {
+        case someDerived instanceof Derived1:
+            someDerived.d;
+            someDerived.basey;
+            break
+        case someDerived instanceof Derived2:
+            someDerived.d;
+            someDerived.other;
+        default:
+            someDerived.d;
+            someDerived.other;
+            const never: never = someDerived;
+    }
+
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue8.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue8.ts
new file mode 100644
index 0000000000000..3572817cba99b
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue8.ts
@@ -0,0 +1,32 @@
+// @strict: true
+// @noEmit: true
+
+function foo(cond1: boolean, cond2: boolean) {
+    switch (true) {
+        case cond1:
+            cond1; // Should be true
+            //  ^?
+            cond2; // Should be boolean
+            //  ^?
+            break;
+
+        case cond2:
+            cond1; // Should be false?
+            //  ^?
+            cond2; // Should be true
+            //  ^?
+            break;
+
+        default:
+            cond1; // Should be false?
+            //  ^?
+            cond2; // Should be false?
+            //  ^?
+            break;
+    }
+
+    cond1; // Should be boolean
+    //  ^?
+    cond2; // Should be boolean
+    //  ^?
+}
diff --git a/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue9.ts b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue9.ts
new file mode 100644
index 0000000000000..1f8942d90b1fb
--- /dev/null
+++ b/tests/cases/compiler/narrowByClauseExpressionInSwitchTrue9.ts
@@ -0,0 +1,20 @@
+// @strict: true
+// @noEmit: true
+
+interface IProps {
+    one: boolean;
+}
+
+class Foo {
+    mine: string = "";
+
+    myMethod(x: IProps) {
+        const { one } = x;
+        switch (true) {
+            case one:
+                break;
+            default:
+                let x = this.mine;
+        }
+    }
+}