Support 'this: readonly' parameter declarations

src/compiler/checker.ts

@@ -256,6 +256,7 @@ namespace ts {
         const neverType = createIntrinsicType(TypeFlags.Never, "never");
         const silentNeverType = createIntrinsicType(TypeFlags.Never, "never");
         const nonPrimitiveType = createIntrinsicType(TypeFlags.NonPrimitive, "object");
+        const readonlyThisType = createIntrinsicType(TypeFlags.Any, "readonly");
 
         const emptyObjectType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
 
@@ -5675,11 +5676,37 @@ namespace ts {
             return indexInfo && !indexInfo.isReadonly ? createIndexInfo(indexInfo.type, true, indexInfo.declaration) : indexInfo;
         }
 
+        function hasReadonlyThisParameter(sig: SignatureDeclaration) {
+            const param = firstOrUndefined(sig.parameters);
+            return param &&
+                param.name.kind === SyntaxKind.Identifier &&
+                (<Identifier>param.name).text === "this" &&
+                param.type &&
+                param.type.kind === SyntaxKind.ReadonlyKeyword;
+        }
+
+        function isReadonlyThisMethod(symbol: Symbol) {
+            if (symbol.flags & SymbolFlags.Method) {
+                for (let i = 0; i < symbol.declarations.length; i++) {
+                    const node = symbol.declarations[i];
+                    if (node.kind === SyntaxKind.MethodDeclaration || node.kind === SyntaxKind.MethodSignature) {
+                        if (!hasReadonlyThisParameter(<SignatureDeclaration>node)) {
+                            return false;
+                        }
+                    }
+                }
+                return true;
+            }
+            return false;
+        }
+
         function resolveReadonlyTypeMembers(type: ReadonlyObjectType) {
             const target = type.type;
             const members = createMap<Symbol>() as SymbolTable;
             for (const symbol of getPropertiesOfObjectType(target)) {
-                members.set(symbol.name, instantiateSymbol(symbol, identityMapper, /*readonly*/ true));
+                if (!(symbol.flags & SymbolFlags.Method) || isReadonlyThisMethod(symbol)) {
+                    members.set(symbol.name, instantiateSymbol(symbol, identityMapper, /*readonly*/ true));
+                }
             }
             const callSignatures = getSignaturesOfType(target, SignatureKind.Call);
             const constructSignatures = getSignaturesOfType(target, SignatureKind.Construct);
@@ -6546,7 +6573,8 @@ namespace ts {
 
         function getThisTypeOfSignature(signature: Signature): Type | undefined {
             if (signature.thisParameter) {
-                return getTypeOfSymbol(signature.thisParameter);
+                const type = getTypeOfSymbol(signature.thisParameter);
+                return type !== readonlyThisType ? type : undefined;
             }
         }
 
@@ -7924,6 +7952,8 @@ namespace ts {
                     return neverType;
                 case SyntaxKind.ObjectKeyword:
                     return nonPrimitiveType;
+                case SyntaxKind.ReadonlyKeyword:
+                    return readonlyThisType;
                 case SyntaxKind.ThisType:
                 case SyntaxKind.ThisKeyword:
                     return getTypeFromThisTypeNode(node);
@@ -12410,9 +12440,9 @@ namespace ts {
             }
 
             if (isClassLike(container.parent)) {
-                const symbol = getSymbolOfNode(container.parent);
-                const type = hasModifier(container, ModifierFlags.Static) ? getTypeOfSymbol(symbol) : (<InterfaceType>getDeclaredTypeOfSymbol(symbol)).thisType;
-                return getFlowTypeOfReference(node, type);
+                const classSymbol = getSymbolOfNode(container.parent);
+                const type = hasModifier(container, ModifierFlags.Static) ? getTypeOfSymbol(classSymbol) : (<InterfaceType>getDeclaredTypeOfSymbol(classSymbol)).thisType;
+                return getFlowTypeOfReference(node, isReadonlyThisMethod(getSymbolOfNode(container)) ? getReadonlyType(type) : type);
             }
 
             if (isInJavaScriptFile(node)) {

src/compiler/parser.ts

@@ -2153,8 +2153,16 @@ namespace ts {
             }
         }
 
-        function parseParameterType(): TypeNode {
+        function nextTokenIsStartOfType() {
+            nextToken();
+            return isStartOfType();
+        }
+
+        function parseParameterType(allowReadonly: boolean): TypeNode {
             if (parseOptional(SyntaxKind.ColonToken)) {
+                if (allowReadonly && token() === SyntaxKind.ReadonlyKeyword && !lookAhead(nextTokenIsStartOfType)) {
+                    return parseTokenNode<TypeNode>();
+                }
                 return parseType();
             }
 
@@ -2169,7 +2177,7 @@ namespace ts {
             const node = <ParameterDeclaration>createNode(SyntaxKind.Parameter);
             if (token() === SyntaxKind.ThisKeyword) {
                 node.name = createIdentifier(/*isIdentifier*/ true);
-                node.type = parseParameterType();
+                node.type = parseParameterType(/*allowReadonly*/ true);
                 return finishNode(node);
             }
 
@@ -2193,7 +2201,7 @@ namespace ts {
             }
 
             node.questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
-            node.type = parseParameterType();
+            node.type = parseParameterType(/*allowReadonly*/ false);
             node.initializer = parseBindingElementInitializer(/*inParameter*/ true);
 
             // Do not check for initializers in an ambient context for parameters. This is not

src/compiler/types.ts

@@ -3351,11 +3351,6 @@ namespace ts {
         type: ObjectType;
     }
 
-    // Readonly type variable (TypeFlags.Readonly)
-    export interface ReadonlyTypeVariable extends Type {
-        type: TypeVariable;
-    }
-
     export interface EvolvingArrayType extends ObjectType {
         elementType: Type;      // Element expressions of evolving array type
         finalArrayType?: Type;  // Final array type of evolving array type
@@ -3425,6 +3420,11 @@ namespace ts {
         constraint?: Type;
     }
 
+    // Readonly type variable (TypeFlags.Readonly)
+    export interface ReadonlyTypeVariable extends TypeVariable {
+        type: TypeVariable;
+    }
+
     // keyof T types (TypeFlags.Index)
     export interface IndexType extends Type {
         type: TypeVariable | UnionOrIntersectionType;