From cf540198e69551bfccdf823f1bec1669a3cc0019 Mon Sep 17 00:00:00 2001
From: Sheetal Nandi <shkamat@microsoft.com>
Date: Wed, 31 Jan 2018 16:22:27 -0800
Subject: [PATCH] Always get diagnostics when emitting irrespective of whether
 its declaration only emit The diagnostics reporting and expression resolution
 caching is quite intermingled at present. Hence when we tried to get the
 declaration output without getting diagnostics, the resolution for functions
 return expression is cached but errors arent reported Symbols arent marked as
 referenced. So at later time when trying to get the diagnostics since the
 expression resolution is cached, it doesnt even go through all checks For now
 get diagnostics irrespective of declaration only output to avoid this issue.
 Fixes #21518

---
 src/compiler/checker.ts               |  6 ++----
 src/compiler/program.ts               |  2 +-
 src/compiler/types.ts                 |  2 +-
 src/harness/unittests/tscWatchMode.ts | 27 +++++++++++++++++++++++++++
 4 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 16b2091733a..a2b0d4b823e 100644
--- a/src/compiler/checker.ts
+++ b/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;
         }
 
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 6ea50b30f6f..e334c1ce80f 100755
--- a/src/compiler/program.ts
+++ b/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");
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 481b91c9276..ce2c10a8dda 100644
--- a/src/compiler/types.ts
+++ b/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;
diff --git a/src/harness/unittests/tscWatchMode.ts b/src/harness/unittests/tscWatchMode.ts
index a2b79b00dc7..6915a6ad37d 100644
--- a/src/harness/unittests/tscWatchMode.ts
+++ b/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", () => {