Always get diagnostics when emitting irrespective of whether its declaration only emit

src/compiler/checker.ts

@@ -749,12 +749,10 @@ namespace ts {
             return _jsxNamespace;
         }
 
-        function getEmitResolver(sourceFile: SourceFile, cancellationToken: CancellationToken, ignoreDiagnostics?: boolean) {
+        function getEmitResolver(sourceFile: SourceFile, cancellationToken: CancellationToken) {
             // Ensure we have all the type information in place for this file so that all the
             // emitter questions of this resolver will return the right information.
-            if (!ignoreDiagnostics) {
-                getDiagnostics(sourceFile, cancellationToken);
-            }
+            getDiagnostics(sourceFile, cancellationToken);
             return emitResolver;
         }
 

src/compiler/program.ts

@@ -1179,7 +1179,7 @@ namespace ts {
             // This is because in the -out scenario all files need to be emitted, and therefore all
             // files need to be type checked. And the way to specify that all files need to be type
             // checked is to not pass the file to getEmitResolver.
-            const emitResolver = getDiagnosticsProducingTypeChecker().getEmitResolver((options.outFile || options.out) ? undefined : sourceFile, cancellationToken, emitOnlyDtsFiles);
+            const emitResolver = getDiagnosticsProducingTypeChecker().getEmitResolver((options.outFile || options.out) ? undefined : sourceFile, cancellationToken);
 
             performance.mark("beforeEmit");
 

src/compiler/types.ts

@@ -2892,7 +2892,7 @@ namespace ts {
         // Should not be called directly.  Should only be accessed through the Program instance.
         /* @internal */ getDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
         /* @internal */ getGlobalDiagnostics(): Diagnostic[];
-        /* @internal */ getEmitResolver(sourceFile?: SourceFile, cancellationToken?: CancellationToken, ignoreDiagnostics?: boolean): EmitResolver;
+        /* @internal */ getEmitResolver(sourceFile?: SourceFile, cancellationToken?: CancellationToken): EmitResolver;
 
         /* @internal */ getNodeCount(): number;
         /* @internal */ getIdentifierCount(): number;

src/harness/unittests/builder.ts

@@ -70,13 +70,6 @@ namespace ts {
             // Change e.ts and verify previously b.js as well as a.js get emitted again since previous change was consumed completely but not d.ts
             program = updateProgramFile(program, "/e.ts", "export function bar3() { }");
             assertChanges(["/b.js", "/a.js", "/e.js"]);
-
-            // Cancel in the middle of affected files list after b.js emit
-            program = updateProgramFile(program, "/b.ts", "export class b { foo2() { c + 1; } }");
-            assertChanges(["/b.js", "/a.js"], 1);
-            // Change e.ts and verify previously b.js as well as a.js get emitted again since previous change was consumed completely but not d.ts
-            program = updateProgramFile(program, "/e.ts", "export function bar5() { }");
-            assertChanges(["/b.js", "/a.js", "/e.js"]);
         });
     });
 

src/harness/unittests/tscWatchMode.ts

@@ -1086,6 +1086,33 @@ namespace ts.tscWatch {
             // This should be 0
             host.checkTimeoutQueueLengthAndRun(0);
         });
+
+        it("shouldnt report error about unused function incorrectly when file changes from global to module", () => {
+            const getFileContent = (asModule: boolean) => `
+                    function one() {}
+                    ${asModule ? "export " : ""}function two() {
+                      return function three() {
+                        one();
+                      }
+                    }`;
+            const file: FileOrFolder = {
+                path: "/a/b/file.ts",
+                content: getFileContent(/*asModule*/ false)
+            };
+            const files = [file, libFile];
+            const host = createWatchedSystem(files);
+            const watch = createWatchOfFilesAndCompilerOptions([file.path], host, {
+                noUnusedLocals: true
+            });
+            checkProgramActualFiles(watch(), files.map(file => file.path));
+            checkOutputErrors(host, [], ExpectedOutputErrorsPosition.AfterCompilationStarting);
+
+            file.content = getFileContent(/*asModule*/ true);
+            host.reloadFS(files);
+            host.runQueuedTimeoutCallbacks();
+            checkProgramActualFiles(watch(), files.map(file => file.path));
+            checkOutputErrors(host, [], ExpectedOutputErrorsPosition.AfterFileChangeDetected);
+        });
     });
 
     describe("tsc-watch emit with outFile or out setting", () => {