Use jsdoc casts

src/compiler/checker.ts

@@ -16256,15 +16256,19 @@ namespace ts {
         }
 
         function checkAssertion(node: AssertionExpression) {
-            const exprType = getRegularTypeOfObjectLiteral(getBaseTypeOfLiteralType(checkExpression(node.expression)));
+            return checkAssertionWorker(node, node.type, node.expression);
+        }
 
-            checkSourceElement(node.type);
-            const targetType = getTypeFromTypeNode(node.type);
+        function checkAssertionWorker(errNode: Node, type: TypeNode, expression: UnaryExpression | Expression, checkMode?: CheckMode) {
+            const exprType = getRegularTypeOfObjectLiteral(getBaseTypeOfLiteralType(checkExpression(expression, checkMode)));
+
+            checkSourceElement(type);
+            const targetType = getTypeFromTypeNode(type);
 
             if (produceDiagnostics && targetType !== unknownType) {
                 const widenedType = getWidenedType(exprType);
                 if (!isTypeComparableTo(targetType, widenedType)) {
-                    checkTypeComparableTo(exprType, targetType, node, Diagnostics.Type_0_cannot_be_converted_to_type_1);
+                    checkTypeComparableTo(exprType, targetType, errNode, Diagnostics.Type_0_cannot_be_converted_to_type_1);
                 }
             }
             return targetType;
@@ -17735,6 +17739,18 @@ namespace ts {
             return type;
         }
 
+        function checkParenthesizedExpression(node: ParenthesizedExpression, checkMode?: CheckMode): Type {
+            if (isInJavaScriptFile(node) && node.jsDoc) {
+                const typecasts = flatMap(node.jsDoc, doc => filter(doc.tags, tag => tag.kind === SyntaxKind.JSDocTypeTag));
+                if (typecasts && typecasts.length) {
+                    // We should have already issued an error if there were multiple type jsdocs
+                    const cast = typecasts[0] as JSDocTypeTag;
+                    return checkAssertionWorker(cast, cast.typeExpression.type, node.expression, checkMode);
+                }
+            }
+            return checkExpression(node.expression, checkMode);
+        }
+
         function checkExpressionWorker(node: Expression, checkMode: CheckMode): Type {
             switch (node.kind) {
                 case SyntaxKind.Identifier:
@@ -17774,7 +17790,7 @@ namespace ts {
                 case SyntaxKind.TaggedTemplateExpression:
                     return checkTaggedTemplateExpression(<TaggedTemplateExpression>node);
                 case SyntaxKind.ParenthesizedExpression:
-                    return checkExpression((<ParenthesizedExpression>node).expression, checkMode);
+                    return checkParenthesizedExpression(<ParenthesizedExpression>node, checkMode);
                 case SyntaxKind.ClassExpression:
                     return checkClassExpression(<ClassExpression>node);
                 case SyntaxKind.FunctionExpression:

src/compiler/parser.ts

@@ -4342,7 +4342,7 @@ namespace ts {
             parseExpected(SyntaxKind.OpenParenToken);
             node.expression = allowInAnd(parseExpression);
             parseExpected(SyntaxKind.CloseParenToken);
-            return finishNode(node);
+            return addJSDocComment(finishNode(node));
         }
 
         function parseSpreadElement(): Expression {

src/compiler/utilities.ts

@@ -640,7 +640,8 @@ namespace ts {
         const commentRanges = (node.kind === SyntaxKind.Parameter ||
             node.kind === SyntaxKind.TypeParameter ||
             node.kind === SyntaxKind.FunctionExpression ||
-            node.kind === SyntaxKind.ArrowFunction) ?
+            node.kind === SyntaxKind.ArrowFunction ||
+            node.kind === SyntaxKind.ParenthesizedExpression) ?
             concatenate(getTrailingCommentRanges(text, node.pos), getLeadingCommentRanges(text, node.pos)) :
             getLeadingCommentRangesOfNodeFromText(node, text);
         // True if the comment starts with '/**' but not if it is '/**/'

tests/baselines/reference/jsdocTypeTagCast.errors.txt

@@ -0,0 +1,129 @@
+tests/cases/conformance/jsdoc/b.js(4,13): error TS2352: Type 'number' cannot be converted to type 'string'.
+tests/cases/conformance/jsdoc/b.js(45,16): error TS2352: Type 'SomeOther' cannot be converted to type 'SomeBase'.
+  Property 'p' is missing in type 'SomeOther'.
+tests/cases/conformance/jsdoc/b.js(49,19): error TS2352: Type 'SomeOther' cannot be converted to type 'SomeDerived'.
+  Property 'x' is missing in type 'SomeOther'.
+tests/cases/conformance/jsdoc/b.js(51,17): error TS2352: Type 'SomeDerived' cannot be converted to type 'SomeOther'.
+  Property 'q' is missing in type 'SomeDerived'.
+tests/cases/conformance/jsdoc/b.js(52,17): error TS2352: Type 'SomeBase' cannot be converted to type 'SomeOther'.
+  Property 'q' is missing in type 'SomeBase'.
+tests/cases/conformance/jsdoc/b.js(58,1): error TS2322: Type '{ p: string | number | undefined; }' is not assignable to type 'SomeBase'.
+  Types of property 'p' are incompatible.
+    Type 'string | number | undefined' is not assignable to type 'number'.
+      Type 'undefined' is not assignable to type 'number'.
+tests/cases/conformance/jsdoc/b.js(66,8): error TS2352: Type 'boolean' cannot be converted to type 'string | number'.
+tests/cases/conformance/jsdoc/b.js(66,15): error TS2304: Cannot find name 'numOrStr'.
+tests/cases/conformance/jsdoc/b.js(66,24): error TS1005: '}' expected.
+tests/cases/conformance/jsdoc/b.js(66,38): error TS2454: Variable 'numOrStr' is used before being assigned.
+tests/cases/conformance/jsdoc/b.js(67,2): error TS2322: Type 'string | number' is not assignable to type 'string'.
+  Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/jsdoc/b.js(67,8): error TS2454: Variable 'numOrStr' is used before being assigned.
+
+
+==== tests/cases/conformance/jsdoc/a.ts (0 errors) ====
+    var W: string;
+
+==== tests/cases/conformance/jsdoc/b.js (12 errors) ====
+    // @ts-check
+    var W = /** @type {string} */(/** @type {*} */ (4));
+
+    var W = /** @type {string} */(4); // Error
+                ~~~~~~~~~~~~~~
+!!! error TS2352: Type 'number' cannot be converted to type 'string'.
+
+    /** @type {*} */
+    var a;
+
+    /** @type {string} */
+    var s;
+
+    var a = /** @type {*} */("" + 4);
+    var s = "" + /** @type {*} */(4);
+
+    class SomeBase {
+        constructor() {
+            this.p = 42;
+        }
+    }
+    class SomeDerived extends SomeBase {
+        constructor() {
+            super();
+            this.x = 42;
+        }
+    }
+    class SomeOther {
+        constructor() {
+            this.q = 42;
+        }
+    }
+
+    function SomeFakeClass() {
+        /** @type {string|number} */
+        this.p = "bar";
+    }
+
+    // Type assertion should check for assignability in either direction
+    var someBase = new SomeBase();
+    var someDerived = new SomeDerived();
+    var someOther = new SomeOther();
+    var someFakeClass = new SomeFakeClass();
+
+    someBase = /** @type {SomeBase} */(someDerived);
+    someBase = /** @type {SomeBase} */(someBase);
+    someBase = /** @type {SomeBase} */(someOther); // Error
+                   ~~~~~~~~~~~~~~~~
+!!! error TS2352: Type 'SomeOther' cannot be converted to type 'SomeBase'.
+!!! error TS2352:   Property 'p' is missing in type 'SomeOther'.
+
+    someDerived = /** @type {SomeDerived} */(someDerived);
+    someDerived = /** @type {SomeDerived} */(someBase);
+    someDerived = /** @type {SomeDerived} */(someOther); // Error
+                      ~~~~~~~~~~~~~~~~~~~
+!!! error TS2352: Type 'SomeOther' cannot be converted to type 'SomeDerived'.
+!!! error TS2352:   Property 'x' is missing in type 'SomeOther'.
+
+    someOther = /** @type {SomeOther} */(someDerived); // Error
+                    ~~~~~~~~~~~~~~~~~
+!!! error TS2352: Type 'SomeDerived' cannot be converted to type 'SomeOther'.
+!!! error TS2352:   Property 'q' is missing in type 'SomeDerived'.
+    someOther = /** @type {SomeOther} */(someBase); // Error
+                    ~~~~~~~~~~~~~~~~~
+!!! error TS2352: Type 'SomeBase' cannot be converted to type 'SomeOther'.
+!!! error TS2352:   Property 'q' is missing in type 'SomeBase'.
+    someOther = /** @type {SomeOther} */(someOther);
+
+    someFakeClass = someBase;
+    someFakeClass = someDerived;
+
+    someBase = someFakeClass; // Error
+    ~~~~~~~~
+!!! error TS2322: Type '{ p: string | number | undefined; }' is not assignable to type 'SomeBase'.
+!!! error TS2322:   Types of property 'p' are incompatible.
+!!! error TS2322:     Type 'string | number | undefined' is not assignable to type 'number'.
+!!! error TS2322:       Type 'undefined' is not assignable to type 'number'.
+    someBase = /** @type {SomeBase} */(someFakeClass);
+
+    // Type assertion cannot be a type-predicate type
+    /** @type {number | string} */
+    var numOrStr;
+    /** @type {string} */
+    var str;
+    if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
+           ~~~~~~~~~~~~~~~
+!!! error TS2352: Type 'boolean' cannot be converted to type 'string | number'.
+                  ~~~~~~~~
+!!! error TS2304: Cannot find name 'numOrStr'.
+                           ~~
+!!! error TS1005: '}' expected.
+                                         ~~~~~~~~
+!!! error TS2454: Variable 'numOrStr' is used before being assigned.
+    	str = numOrStr; // Error, no narrowing occurred
+    	~~~
+!!! error TS2322: Type 'string | number' is not assignable to type 'string'.
+!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+    	      ~~~~~~~~
+!!! error TS2454: Variable 'numOrStr' is used before being assigned.
+    }
+
+
+

tests/baselines/reference/jsdocTypeTagCast.js

@@ -0,0 +1,151 @@
+//// [tests/cases/conformance/jsdoc/jsdocTypeTagCast.ts] ////
+
+//// [a.ts]
+var W: string;
+
+//// [b.js]
+// @ts-check
+var W = /** @type {string} */(/** @type {*} */ (4));
+
+var W = /** @type {string} */(4); // Error
+
+/** @type {*} */
+var a;
+
+/** @type {string} */
+var s;
+
+var a = /** @type {*} */("" + 4);
+var s = "" + /** @type {*} */(4);
+
+class SomeBase {
+    constructor() {
+        this.p = 42;
+    }
+}
+class SomeDerived extends SomeBase {
+    constructor() {
+        super();
+        this.x = 42;
+    }
+}
+class SomeOther {
+    constructor() {
+        this.q = 42;
+    }
+}
+
+function SomeFakeClass() {
+    /** @type {string|number} */
+    this.p = "bar";
+}
+
+// Type assertion should check for assignability in either direction
+var someBase = new SomeBase();
+var someDerived = new SomeDerived();
+var someOther = new SomeOther();
+var someFakeClass = new SomeFakeClass();
+
+someBase = /** @type {SomeBase} */(someDerived);
+someBase = /** @type {SomeBase} */(someBase);
+someBase = /** @type {SomeBase} */(someOther); // Error
+
+someDerived = /** @type {SomeDerived} */(someDerived);
+someDerived = /** @type {SomeDerived} */(someBase);
+someDerived = /** @type {SomeDerived} */(someOther); // Error
+
+someOther = /** @type {SomeOther} */(someDerived); // Error
+someOther = /** @type {SomeOther} */(someBase); // Error
+someOther = /** @type {SomeOther} */(someOther);
+
+someFakeClass = someBase;
+someFakeClass = someDerived;
+
+someBase = someFakeClass; // Error
+someBase = /** @type {SomeBase} */(someFakeClass);
+
+// Type assertion cannot be a type-predicate type
+/** @type {number | string} */
+var numOrStr;
+/** @type {string} */
+var str;
+if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
+	str = numOrStr; // Error, no narrowing occurred
+}
+
+
+
+
+//// [a.js]
+var W;
+//// [b.js]
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = Object.setPrototypeOf ||
+        ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+        function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+// @ts-check
+var W = ((4));
+var W = (4); // Error
+/** @type {*} */
+var a;
+/** @type {string} */
+var s;
+var a = ("" + 4);
+var s = "" + (4);
+var SomeBase = (function () {
+    function SomeBase() {
+        this.p = 42;
+    }
+    return SomeBase;
+}());
+var SomeDerived = (function (_super) {
+    __extends(SomeDerived, _super);
+    function SomeDerived() {
+        var _this = _super.call(this) || this;
+        _this.x = 42;
+        return _this;
+    }
+    return SomeDerived;
+}(SomeBase));
+var SomeOther = (function () {
+    function SomeOther() {
+        this.q = 42;
+    }
+    return SomeOther;
+}());
+function SomeFakeClass() {
+    /** @type {string|number} */
+    this.p = "bar";
+}
+// Type assertion should check for assignability in either direction
+var someBase = new SomeBase();
+var someDerived = new SomeDerived();
+var someOther = new SomeOther();
+var someFakeClass = new SomeFakeClass();
+someBase = (someDerived);
+someBase = (someBase);
+someBase = (someOther); // Error
+someDerived = (someDerived);
+someDerived = (someBase);
+someDerived = (someOther); // Error
+someOther = (someDerived); // Error
+someOther = (someBase); // Error
+someOther = (someOther);
+someFakeClass = someBase;
+someFakeClass = someDerived;
+someBase = someFakeClass; // Error
+someBase = (someFakeClass);
+// Type assertion cannot be a type-predicate type
+/** @type {number | string} */
+var numOrStr;
+/** @type {string} */
+var str;
+if ((numOrStr === undefined)) {
+    str = numOrStr; // Error, no narrowing occurred
+}