Error when emitted type in declaration file references inaccessible 'this'

src/compiler/checker.ts

@@ -1606,12 +1606,10 @@ namespace ts {
                             : (<IntrinsicType>type).intrinsicName);
                     }
                     else if (type.flags & TypeFlags.ThisType) {
-                        if (inObjectTypeLiteral && globalFlags & TypeFormatFlags.RewriteInaccessibleThis) {
-                            writeType((<TypeParameter>type).constraint, flags);
-                        }
-                        else {
-                            writer.writeKeyword("this");
+                        if (inObjectTypeLiteral) {
+                            writer.reportInaccessibleThisError();
                         }
+                        writer.writeKeyword("this");
                     }
                     else if (type.flags & TypeFlags.Reference) {
                         writeTypeReference(<TypeReference>type, flags);
@@ -14682,17 +14680,17 @@ namespace ts {
                 ? getTypeOfSymbol(symbol)
                 : unknownType;
 
-            getSymbolDisplayBuilder().buildTypeDisplay(type, writer, enclosingDeclaration, flags | TypeFormatFlags.RewriteInaccessibleThis);
+            getSymbolDisplayBuilder().buildTypeDisplay(type, writer, enclosingDeclaration, flags);
         }
 
         function writeReturnTypeOfSignatureDeclaration(signatureDeclaration: SignatureDeclaration, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: SymbolWriter) {
             let signature = getSignatureFromDeclaration(signatureDeclaration);
-            getSymbolDisplayBuilder().buildTypeDisplay(getReturnTypeOfSignature(signature), writer, enclosingDeclaration, flags | TypeFormatFlags.RewriteInaccessibleThis);
+            getSymbolDisplayBuilder().buildTypeDisplay(getReturnTypeOfSignature(signature), writer, enclosingDeclaration, flags);
         }
 
         function writeTypeOfExpression(expr: Expression, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: SymbolWriter) {
             let type = getTypeOfExpression(expr);
-            getSymbolDisplayBuilder().buildTypeDisplay(type, writer, enclosingDeclaration, flags | TypeFormatFlags.RewriteInaccessibleThis);
+            getSymbolDisplayBuilder().buildTypeDisplay(type, writer, enclosingDeclaration, flags);
         }
 
         function hasGlobalName(name: string): boolean {

src/compiler/declarationEmitter.ts

@@ -52,6 +52,7 @@ namespace ts {
         let enclosingDeclaration: Node;
         let currentSourceFile: SourceFile;
         let reportedDeclarationError = false;
+        let errorNameNode: DeclarationName;
         let emitJsDocComments = compilerOptions.removeComments ? function (declaration: Node) { } : writeJsDocComments;
         let emit = compilerOptions.stripInternal ? stripInternal : emitNode;
 
@@ -152,6 +153,7 @@ namespace ts {
         function createAndSetNewTextWriterWithSymbolWriter(): EmitTextWriterWithSymbolWriter {
             let writer = <EmitTextWriterWithSymbolWriter>createTextWriter(newLine);
             writer.trackSymbol = trackSymbol;
+            writer.reportInaccessibleThisError = reportInaccessibleThisError;
             writer.writeKeyword = writer.write;
             writer.writeOperator = writer.write;
             writer.writePunctuation = writer.write;
@@ -257,6 +259,13 @@ namespace ts {
             handleSymbolAccessibilityError(resolver.isSymbolAccessible(symbol, enclosingDeclaration, meaning));
         }
 
+        function reportInaccessibleThisError() {
+            if (errorNameNode) {
+                diagnostics.push(createDiagnosticForNode(errorNameNode, Diagnostics.The_inferred_type_of_0_references_an_inaccessible_this_type_A_type_annotation_is_necessary,
+                    declarationNameToString(errorNameNode)));
+            }
+        }
+
         function writeTypeOfDeclaration(declaration: AccessorDeclaration | VariableLikeDeclaration, type: TypeNode, getSymbolAccessibilityDiagnostic: GetSymbolAccessibilityDiagnostic) {
             writer.getSymbolAccessibilityDiagnostic = getSymbolAccessibilityDiagnostic;
             write(": ");
@@ -265,7 +274,9 @@ namespace ts {
                 emitType(type);
             }
             else {
+                errorNameNode = declaration.name;
                 resolver.writeTypeOfDeclaration(declaration, enclosingDeclaration, TypeFormatFlags.UseTypeOfFunction, writer);
+                errorNameNode = undefined;
             }
         }
 
@@ -277,7 +288,9 @@ namespace ts {
                 emitType(signature.type);
             }
             else {
+                errorNameNode = signature.name;
                 resolver.writeReturnTypeOfSignatureDeclaration(signature, enclosingDeclaration, TypeFormatFlags.UseTypeOfFunction, writer);
+                errorNameNode = undefined;
             }
         }
 

src/compiler/diagnosticMessages.json

@@ -1656,6 +1656,10 @@
         "category": "Error",
         "code": 2526
     },
+    "The inferred type of '{0}' references an inaccessible 'this' type. A type annotation is necessary.": {
+        "category": "Error",
+        "code": 2527
+    },
     "JSX element attributes type '{0}' must be an object type.": {
         "category": "Error",
         "code": 2600

src/compiler/types.ts

@@ -1497,6 +1497,7 @@ namespace ts {
         // declaration emitter to help determine if it should patch up the final declaration file
         // with import statements it previously saw (but chose not to emit).
         trackSymbol(symbol: Symbol, enclosingDeclaration?: Node, meaning?: SymbolFlags): void;
+        reportInaccessibleThisError(): void;
     }
 
     export const enum TypeFormatFlags {
@@ -1509,7 +1510,6 @@ namespace ts {
         WriteTypeArgumentsOfSignature   = 0x00000020,  // Write the type arguments instead of type parameters of the signature
         InElementType                   = 0x00000040,  // Writing an array or union element type
         UseFullyQualifiedType           = 0x00000080,  // Write out the fully qualified type name (eg. Module.Type, instead of Type)
-        RewriteInaccessibleThis         = 0x00000100,  // Rewrite references to inaccessible "this"
     }
 
     export const enum SymbolFormatFlags {

src/compiler/utilities.ts

@@ -65,7 +65,8 @@ namespace ts {
                 increaseIndent: () => { },
                 decreaseIndent: () => { },
                 clear: () => str = "",
-                trackSymbol: () => { }
+                trackSymbol: () => { },
+                reportInaccessibleThisError: () => { }
             };
         }
 

src/services/utilities.ts

@@ -626,7 +626,8 @@ namespace ts {
             increaseIndent: () => { indent++; },
             decreaseIndent: () => { indent--; },
             clear: resetWriter,
-            trackSymbol: () => { }
+            trackSymbol: () => { },
+            reportInaccessibleThisError: () => { }
         };
 
         function writeIndent() {