From bb975aff3ef32cd6ea2f063f2d981e716be612b2 Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wewigham@microsoft.com>
Date: Fri, 16 Nov 2018 15:03:35 -0800
Subject: [PATCH 1/2] getTypeChecker returns the same checker manufactured for
 diagnostics if it has already been made

---
 src/compiler/program.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 15c09a1a79ba5..705d9fcb461f2 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -1376,7 +1376,7 @@ namespace ts {
         }
 
         function getTypeChecker() {
-            return noDiagnosticsTypeChecker || (noDiagnosticsTypeChecker = createTypeChecker(program, /*produceDiagnostics:*/ false));
+            return noDiagnosticsTypeChecker || (noDiagnosticsTypeChecker = diagnosticsProducingTypeChecker || createTypeChecker(program, /*produceDiagnostics:*/ false));
         }
 
         function emit(sourceFile?: SourceFile, writeFileCallback?: WriteFileCallback, cancellationToken?: CancellationToken, emitOnlyDtsFiles?: boolean, transformers?: CustomTransformers): EmitResult {

From c2cae1d19792c24d7778fa9acbbb6453d317a275 Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wewigham@microsoft.com>
Date: Fri, 16 Nov 2018 16:03:41 -0800
Subject: [PATCH 2/2] Drop (heh) vestigial API

---
 src/compiler/program.ts   | 5 -----
 src/compiler/types.ts     | 1 -
 src/harness/harness.ts    | 2 +-
 src/harness/typeWriter.ts | 8 ++------
 4 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 705d9fcb461f2..c23d09f768e86 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -797,7 +797,6 @@ namespace ts {
             getResolvedTypeReferenceDirectives: () => resolvedTypeReferenceDirectives,
             isSourceFileFromExternalLibrary,
             isSourceFileDefaultLibrary,
-            dropDiagnosticsProducingTypeChecker,
             getSourceFileFromReference,
             getLibFileFromReference,
             sourceFileToPackageName,
@@ -1371,10 +1370,6 @@ namespace ts {
             return diagnosticsProducingTypeChecker || (diagnosticsProducingTypeChecker = createTypeChecker(program, /*produceDiagnostics:*/ true));
         }
 
-        function dropDiagnosticsProducingTypeChecker() {
-            diagnosticsProducingTypeChecker = undefined!;
-        }
-
         function getTypeChecker() {
             return noDiagnosticsTypeChecker || (noDiagnosticsTypeChecker = diagnosticsProducingTypeChecker || createTypeChecker(program, /*produceDiagnostics:*/ false));
         }
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index b4c405c31742a..61d1e5e95901f 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2886,7 +2886,6 @@ namespace ts {
         // For testing purposes only.  Should not be used by any other consumers (including the
         // language service).
         /* @internal */ getDiagnosticsProducingTypeChecker(): TypeChecker;
-        /* @internal */ dropDiagnosticsProducingTypeChecker(): void;
 
         /* @internal */ getClassifiableNames(): UnderscoreEscapedMap<true>;
 
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index fc275529258bb..60f1eeb02f830 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -1507,7 +1507,7 @@ namespace Harness {
             // These types are equivalent, but depend on what order the compiler observed
             // certain parts of the program.
 
-            const fullWalker = new TypeWriterWalker(program, /*fullTypeCheck*/ true, !!hasErrorBaseline);
+            const fullWalker = new TypeWriterWalker(program, !!hasErrorBaseline);
 
             // Produce baselines.  The first gives the types for all expressions.
             // The second gives symbols for all identifiers.
diff --git a/src/harness/typeWriter.ts b/src/harness/typeWriter.ts
index 67f79a1a1a3c6..179873fdf1762 100644
--- a/src/harness/typeWriter.ts
+++ b/src/harness/typeWriter.ts
@@ -25,12 +25,8 @@ class TypeWriterWalker {
 
     private checker: ts.TypeChecker;
 
-    constructor(private program: ts.Program, fullTypeCheck: boolean, private hadErrorBaseline: boolean) {
-        // Consider getting both the diagnostics checker and the non-diagnostics checker to verify
-        // they are consistent.
-        this.checker = fullTypeCheck
-            ? program.getDiagnosticsProducingTypeChecker()
-            : program.getTypeChecker();
+    constructor(private program: ts.Program, private hadErrorBaseline: boolean) {
+        this.checker = program.getDiagnosticsProducingTypeChecker();
     }
 
     public *getSymbols(fileName: string): IterableIterator<TypeWriterSymbolResult> {