Forbid the flag of --out, --outFile with the use of --isolatedDeclarations

src/compiler/program.ts

@@ -4169,6 +4169,16 @@ export function createProgram(rootNamesOrOptions: readonly string[] | CreateProg
             }
         }
 
+        if (options.isolatedDeclarations) {
+            if (options.out) {
+                createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_with_option_1, "out", "isolatedDeclarations");
+            }
+
+            if (options.outFile) {
+                createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_with_option_1, "outFile", "isolatedDeclarations");
+            }
+        }
+
         if (options.inlineSourceMap) {
             if (options.sourceMap) {
                 createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_with_option_1, "sourceMap", "inlineSourceMap");

tests/baselines/reference/isolatedDeclarations.errors.txt

@@ -0,0 +1,8 @@
+error TS5053: Option 'outFile' cannot be specified with option 'isolatedDeclarations'.
+
+
+!!! error TS5053: Option 'outFile' cannot be specified with option 'isolatedDeclarations'.
+==== file1.ts (0 errors) ====
+    export var x;
+==== file2.ts (0 errors) ====
+    var y;

tests/baselines/reference/isolatedDeclarations.js

@@ -0,0 +1,14 @@
+//// [tests/cases/compiler/isolatedDeclarations.ts] ////
+
+//// [file1.ts]
+export var x;
+//// [file2.ts]
+var y;
+
+//// [all.js]
+define("file1", ["require", "exports"], function (require, exports) {
+    "use strict";
+    Object.defineProperty(exports, "__esModule", { value: true });
+    exports.x = void 0;
+});
+var y;

tests/baselines/reference/isolatedDeclarations.symbols

@@ -0,0 +1,10 @@
+//// [tests/cases/compiler/isolatedDeclarations.ts] ////
+
+=== file1.ts ===
+export var x;
+>x : Symbol(x, Decl(file1.ts, 0, 10))
+
+=== file2.ts ===
+var y;
+>y : Symbol(y, Decl(file2.ts, 0, 3))
+

tests/baselines/reference/isolatedDeclarations.types

@@ -0,0 +1,10 @@
+//// [tests/cases/compiler/isolatedDeclarations.ts] ////
+
+=== file1.ts ===
+export var x;
+>x : any
+
+=== file2.ts ===
+var y;
+>y : any
+

tests/cases/compiler/isolatedDeclarations.ts

@@ -0,0 +1,9 @@
+// @isolatedDeclarations: true
+// @outFile:all.js
+// @target: es6
+// @module: amd
+
+// @filename: file1.ts
+export var x;
+// @filename: file2.ts
+var y;