Refine diagnostic for switch expression that is not exhaustive

Fixes dotnet#38571

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -5661,10 +5661,10 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
     <value>The syntax 'var' for a pattern is not permitted to refer to a type, but '{0}' is in scope here.</value>
   </data>
   <data name="WRN_SwitchExpressionNotExhaustive" xml:space="preserve">
-    <value>The switch expression does not handle all possible inputs (it is not exhaustive).</value>
+    <value>The switch expression does not handle all possible values of its input type (it is not exhaustive).</value>
   </data>
   <data name="WRN_SwitchExpressionNotExhaustive_Title" xml:space="preserve">
-    <value>The switch expression does not handle all possible inputs (it is not exhaustive).</value>
+    <value>The switch expression does not handle all possible values of its input type (it is not exhaustive).</value>
   </data>
   <data name="WRN_CaseConstantNamedUnderscore" xml:space="preserve">
     <value>The name '_' refers to the constant, not the discard pattern. Use 'var _' to discard the value, or '@_' to refer to a constant by that name.</value>

src/Compilers/CSharp/Test/Emit/CodeGen/PatternTests.cs

@@ -3026,7 +3026,7 @@ static class C {
 ";
             var compilation = CreateEmptyCompilation(source, options: TestOptions.ReleaseDll);
             compilation.GetDiagnostics().Verify(
-                // (9,38): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (9,38): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //     public static bool M(int i) => i switch { 1 => true };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(9, 38)
                 );
@@ -3036,7 +3036,7 @@ static class C {
                 // (9,36): error CS0656: Missing compiler required member 'System.InvalidOperationException..ctor'
                 //     public static bool M(int i) => i switch { 1 => true };
                 Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "i switch { 1 => true }").WithArguments("System.InvalidOperationException", ".ctor").WithLocation(9, 36),
-                // (9,38): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (9,38): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //     public static bool M(int i) => i switch { 1 => true };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(9, 38)
                 );

src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_ISwitchExpression.cs

@@ -74,7 +74,7 @@ void M(int? x, object y)
   Arms(0)
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         y = /*<bind>*/x switch { }/*</bind>*/;
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 25)
             };
@@ -110,7 +110,7 @@ void M(int? x, object y)
           ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 5) (Syntax: '5')
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         y = /*<bind>*/x switch { => 5 }/*</bind>*/;
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 25),
                 // file.cs(7,34): error CS8504: Pattern missing
@@ -355,7 +355,7 @@ void M(int? x, object y)
           ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 5) (Syntax: '5')
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         y = /*<bind>*/x switch { NotFound => 5 }/*</bind>*/;
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 25),
                 // file.cs(7,34): error CS0103: The name 'NotFound' does not exist in the current context
@@ -512,7 +512,7 @@ void M(int? x, object y)
           ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 5) (Syntax: '5')
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         y = /*<bind>*/x switch { 1 => 2, _ when false => 5 }/*</bind>*/;
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 25)
             };
@@ -589,7 +589,7 @@ void M(int? x, object y)
           ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 5) (Syntax: '5')
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         y = /*<bind>*/x switch { _ when NotFound => 5 }/*</bind>*/;
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 25),
                 // file.cs(7,41): error CS0103: The name 'NotFound' does not exist in the current context
@@ -636,7 +636,7 @@ void M(int? x, object y)
           Local_2: System.Int32 z
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(7,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         y = /*<bind>*/x switch { int z when x is int z => 5 }/*</bind>*/;
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 25),
                 // file.cs(7,54): error CS0128: A local variable or function named 'z' is already defined in this scope

src/Compilers/CSharp/Test/IOperation/IOperation/IOperationTests_ISwitchOperation.cs

@@ -3324,7 +3324,7 @@ public static void Main()
 }
 ";
             var expectedDiagnostics = new[] {
-                // file.cs(6,19): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // file.cs(6,19): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         var r = 1 switch { };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(6, 19),
                 // file.cs(6,19): error CS8506: No best type was found for the switch expression.

src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTests2.cs

@@ -494,7 +494,7 @@ public static void Main()
     }
 }";
             CreatePatternCompilation(source).VerifyDiagnostics(
-                // (5,19): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (5,19): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         var r = 1 switch { };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(5, 19),
                 // (5,19): error CS8506: No best type was found for the switch expression.
@@ -518,7 +518,7 @@ public static void M() {}
     public delegate void D();
 }";
             CreatePatternCompilation(source).VerifyDiagnostics(
-                // (5,19): warning CS8409: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (5,19): warning CS8409: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         var x = 1 switch { 0 => M, 1 => new D(M), 2 => M };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(5, 19)
                 );
@@ -609,7 +609,7 @@ public static void Main()
 }";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (7,19): warning CS8409: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (7,19): warning CS8409: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         var c = a switch { var x2 when x2 is var x3 => x3 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 19)
                 );

src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTests3.cs

@@ -542,7 +542,7 @@ ref int M(bool b, ref int x, ref int y)
 }";
             var compilation = CreateCompilationWithMscorlibAndSpan(source, options: TestOptions.DebugDll);
             compilation.VerifyDiagnostics(
-                // (6,23): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (6,23): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         return ref (b switch { true => ref x, false => ref y });
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(6, 23),
                 // (6,40): error CS1525: Invalid expression term 'ref'

src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTests4.cs

@@ -1776,7 +1776,7 @@ static int M1(bool? b1, bool? b2)
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (6,25): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (6,25): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         return (b1, b2) switch {
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(6, 25)
                 );
@@ -2048,7 +2048,7 @@ static void Main()
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (9,19): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (9,19): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //             _ = t switch { (3, 4) => 1 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(9, 19)
                 );
@@ -2091,7 +2091,7 @@ public SwitchExpressionException() {}
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (9,19): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (9,19): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //             _ = t switch { (3, 4) => 1 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(9, 19)
                 );
@@ -2134,7 +2134,7 @@ public class SwitchExpressionException : InvalidOperationException
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (9,19): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (9,19): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //             _ = t switch { (3, 4) => 1 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(9, 19)
                 );
@@ -2176,7 +2176,7 @@ public class SwitchExpressionException : InvalidOperationException
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (8,24): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (8,24): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //             _ = (1, 2) switch { (3, 4) => 1 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(8, 24)
                 );
@@ -2223,7 +2223,7 @@ public SwitchExpressionException() {}
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (9,19): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (9,19): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //             _ = r switch { (3, 4) => 1 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(9, 19)
                 );
@@ -2815,7 +2815,7 @@ public static void Main()
 ";
             var compilation = CreatePatternCompilation(source, options: TestOptions.ReleaseExe);
             compilation.VerifyDiagnostics(
-                // (7,32): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (7,32): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         Console.Write((x, 300) switch  { ((1, int x2), int y) => x2+y });
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(7, 32)
                 );
@@ -2891,7 +2891,7 @@ public static void Main()
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (6,15): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (6,15): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         _ = o switch { null => 1 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(6, 15)
                 );
@@ -2930,7 +2930,7 @@ public int M(bool b)
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (22,18): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (22,18): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         return b switch
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(22, 18)
                 );
@@ -3082,7 +3082,7 @@ public class SwitchExpressionException : InvalidOperationException
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (17,23): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (17,23): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         return (x, y) switch { (1, 2) => 3 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(17, 23)
                 );
@@ -3218,7 +3218,7 @@ public class SwitchExpressionException : InvalidOperationException
 ";
             var compilation = CreatePatternCompilation(source);
             compilation.VerifyDiagnostics(
-                // (17,44): warning CS8509: The switch expression does not handle all possible inputs (it is not exhaustive).
+                // (17,44): warning CS8509: The switch expression does not handle all possible values of its input type (it is not exhaustive).
                 //         return (x, y, a, b, c, d, e, f, g) switch { (1, 2, _, _, _, _, _, _, _) => 3 };
                 Diagnostic(ErrorCode.WRN_SwitchExpressionNotExhaustive, "switch").WithLocation(17, 44)
                 );