Fix 'as const'-like behavior in JSDoc type cast

Author: rbuckton

src/compiler/checker.ts

@@ -8388,12 +8388,12 @@ namespace ts {
         }
 
         function isNullOrUndefined(node: Expression) {
-            const expr = skipParentheses(node);
+            const expr = skipParentheses(node, /*excludeJSDocTypeAssertions*/ true);
             return expr.kind === SyntaxKind.NullKeyword || expr.kind === SyntaxKind.Identifier && getResolvedSymbol(expr as Identifier) === undefinedSymbol;
         }
 
         function isEmptyArrayLiteral(node: Expression) {
-            const expr = skipParentheses(node);
+            const expr = skipParentheses(node, /*excludeJSDocTypeAssertions*/ true);
             return expr.kind === SyntaxKind.ArrayLiteralExpression && (expr as ArrayLiteralExpression).elements.length === 0;
         }
 
@@ -22956,7 +22956,7 @@ namespace ts {
         }
 
         function isFalseExpression(expr: Expression): boolean {
-            const node = skipParentheses(expr);
+            const node = skipParentheses(expr, /*excludeJSDocTypeAssertions*/ true);
             return node.kind === SyntaxKind.FalseKeyword || node.kind === SyntaxKind.BinaryExpression && (
                 (node as BinaryExpression).operatorToken.kind === SyntaxKind.AmpersandAmpersandToken && (isFalseExpression((node as BinaryExpression).left) || isFalseExpression((node as BinaryExpression).right)) ||
                 (node as BinaryExpression).operatorToken.kind === SyntaxKind.BarBarToken && isFalseExpression((node as BinaryExpression).left) && isFalseExpression((node as BinaryExpression).right));
@@ -23278,7 +23278,7 @@ namespace ts {
             }
 
             function narrowTypeByAssertion(type: Type, expr: Expression): Type {
-                const node = skipParentheses(expr);
+                const node = skipParentheses(expr, /*excludeJSDocTypeAssertions*/ true);
                 if (node.kind === SyntaxKind.FalseKeyword) {
                     return unreachableNeverType;
                 }
@@ -25858,7 +25858,9 @@ namespace ts {
                 case SyntaxKind.ParenthesizedExpression: {
                     // Like in `checkParenthesizedExpression`, an `/** @type {xyz} */` comment before a parenthesized expression acts as a type cast.
                     const tag = isInJSFile(parent) ? getJSDocTypeTag(parent) : undefined;
-                    return tag ? getTypeFromTypeNode(tag.typeExpression.type) : getContextualType(parent as ParenthesizedExpression, contextFlags);
+                    return !tag ? getContextualType(parent as ParenthesizedExpression, contextFlags) :
+                        isJSDocTypeTag(tag) && isConstTypeReference(tag.typeExpression.type) ? tryFindWhenConstTypeReference(parent as ParenthesizedExpression) :
+                        getTypeFromTypeNode(tag.typeExpression.type);
                 }
                 case SyntaxKind.NonNullExpression:
                     return getContextualType(parent as NonNullExpression, contextFlags);
@@ -32768,8 +32770,10 @@ namespace ts {
         }
 
         function isTypeAssertion(node: Expression) {
-            node = skipParentheses(node);
-            return node.kind === SyntaxKind.TypeAssertionExpression || node.kind === SyntaxKind.AsExpression;
+            node = skipParentheses(node, /*excludeJSDocTypeAssertions*/ true);
+            return node.kind === SyntaxKind.TypeAssertionExpression ||
+                node.kind === SyntaxKind.AsExpression ||
+                isJSDocTypeAssertion(node);
         }
 
         function checkDeclarationInitializer(declaration: HasExpressionInitializer, contextualType?: Type | undefined) {
@@ -32844,6 +32848,7 @@ namespace ts {
         function isConstContext(node: Expression): boolean {
             const parent = node.parent;
             return isAssertionExpression(parent) && isConstTypeReference(parent.type) ||
+                isJSDocTypeAssertion(parent) && isConstTypeReference(getJSDocTypeAssertionType(parent)) ||
                 (isParenthesizedExpression(parent) || isArrayLiteralExpression(parent) || isSpreadElement(parent)) && isConstContext(parent) ||
                 (isPropertyAssignment(parent) || isShorthandPropertyAssignment(parent) || isTemplateSpan(parent)) && isConstContext(parent.parent);
         }
@@ -33056,7 +33061,14 @@ namespace ts {
         }
 
         function getQuickTypeOfExpression(node: Expression) {
-            const expr = skipParentheses(node);
+            let expr = skipParentheses(node, /*excludeJSDocTypeAssertions*/ true);
+            if (isJSDocTypeAssertion(expr)) {
+                const type = getJSDocTypeAssertionType(expr);
+                if (!isConstTypeReference(type)) {
+                    return getTypeFromTypeNode(type);
+                }
+            }
+            expr = skipParentheses(node);
             // Optimize for the common case of a call to a function with a single non-generic call
             // signature where we can just fetch the return type without checking the arguments.
             if (isCallExpression(expr) && expr.expression.kind !== SyntaxKind.SuperKeyword && !isRequireCall(expr, /*checkArgumentIsStringLiteralLike*/ true) && !isSymbolOrSymbolForCall(expr)) {
@@ -33143,9 +33155,9 @@ namespace ts {
         }
 
         function checkParenthesizedExpression(node: ParenthesizedExpression, checkMode?: CheckMode): Type {
-            const tag = isInJSFile(node) ? getJSDocTypeTag(node) : undefined;
-            if (tag) {
-                return checkAssertionWorker(tag.typeExpression.type, tag.typeExpression.type, node.expression, checkMode);
+            if (isJSDocTypeAssertion(node)) {
+                const type = getJSDocTypeAssertionType(node);
+                return checkAssertionWorker(type, type, node.expression, checkMode);
             }
             return checkExpression(node.expression, checkMode);
         }
@@ -36093,7 +36105,7 @@ namespace ts {
             if (getFalsyFlags(type)) return;
 
             const location = isBinaryExpression(condExpr) ? condExpr.right : condExpr;
-            if (isPropertyAccessExpression(location) && isAssertionExpression(skipParentheses(location.expression))) {
+            if (isPropertyAccessExpression(location) && isTypeAssertion(location.expression)) {
                 return;
             }
 

src/compiler/factory/utilities.ts

@@ -416,9 +416,24 @@ namespace ts {
             node.kind === SyntaxKind.CommaListExpression;
     }
 
+    export function isJSDocTypeAssertion(node: Node): node is JSDocTypeAssertion {
+        return isParenthesizedExpression(node)
+            && isInJSFile(node)
+            && !!getJSDocTypeTag(node);
+    }
+
+    export function getJSDocTypeAssertionType(node: JSDocTypeAssertion) {
+        const type = getJSDocType(node);
+        Debug.assertIsDefined(type);
+        return type;
+    }
+
     export function isOuterExpression(node: Node, kinds = OuterExpressionKinds.All): node is OuterExpression {
         switch (node.kind) {
             case SyntaxKind.ParenthesizedExpression:
+                if (kinds & OuterExpressionKinds.ExcludeJSDocTypeAssertion && isJSDocTypeAssertion(node)) {
+                    return false;
+                }
                 return (kinds & OuterExpressionKinds.Parentheses) !== 0;
             case SyntaxKind.TypeAssertionExpression:
             case SyntaxKind.AsExpression:

src/compiler/types.ts

@@ -2253,6 +2253,11 @@ namespace ts {
         readonly expression: Expression;
     }
 
+    /* @internal */
+    export interface JSDocTypeAssertion extends ParenthesizedExpression {
+        readonly _jsDocTypeAssertionBrand: never;
+    }
+
     export interface ArrayLiteralExpression extends PrimaryExpression {
         readonly kind: SyntaxKind.ArrayLiteralExpression;
         readonly elements: NodeArray<Expression>;
@@ -6889,7 +6894,9 @@ namespace ts {
         PartiallyEmittedExpressions = 1 << 3,
 
         Assertions = TypeAssertions | NonNullAssertions,
-        All = Parentheses | Assertions | PartiallyEmittedExpressions
+        All = Parentheses | Assertions | PartiallyEmittedExpressions,
+
+        ExcludeJSDocTypeAssertion = 1 << 4,
     }
 
     /* @internal */

src/compiler/utilities.ts

@@ -2634,13 +2634,13 @@ namespace ts {
         let result: (JSDoc | JSDocTag)[] | undefined;
         // Pull parameter comments from declaring function as well
         if (isVariableLike(hostNode) && hasInitializer(hostNode) && hasJSDocNodes(hostNode.initializer!)) {
-            result = append(result, last((hostNode.initializer as HasJSDoc).jsDoc!));
+            result = addRange(result, filterOwnedJSDocTags(hostNode, last((hostNode.initializer as HasJSDoc).jsDoc!)));
         }
 
         let node: Node | undefined = hostNode;
         while (node && node.parent) {
             if (hasJSDocNodes(node)) {
-                result = append(result, last(node.jsDoc!));
+                result = addRange(result, filterOwnedJSDocTags(hostNode, last(node.jsDoc!)));
             }
 
             if (node.kind === SyntaxKind.Parameter) {
@@ -2656,6 +2656,26 @@ namespace ts {
         return result || emptyArray;
     }
 
+    function filterOwnedJSDocTags(hostNode: Node, jsDoc: JSDoc | JSDocTag) {
+        if (isJSDoc(jsDoc)) {
+            const ownedTags = filter(jsDoc.tags, tag => ownsJSDocTag(hostNode, tag));
+            return jsDoc.tags === ownedTags ? [jsDoc] : ownedTags;
+        }
+        return ownsJSDocTag(hostNode, jsDoc) ? [jsDoc] : undefined;
+    }
+
+    /**
+     * Determines whether a host node owns a jsDoc tag. A `@type` tag attached to a
+     * a ParenthesizedExpression belongs only to the ParenthesizedExpression.
+     */
+    function ownsJSDocTag(hostNode: Node, tag: JSDocTag) {
+        return !isJSDocTypeTag(tag)
+            || !tag.parent
+            || !isJSDoc(tag.parent)
+            || !isParenthesizedExpression(tag.parent.parent)
+            || tag.parent.parent === hostNode;
+    }
+
     export function getNextJSDocCommentLocation(node: Node) {
         const parent = node.parent;
         if (parent.kind === SyntaxKind.PropertyAssignment ||
@@ -2899,10 +2919,13 @@ namespace ts {
         return [child, node];
     }
 
-    export function skipParentheses(node: Expression): Expression;
-    export function skipParentheses(node: Node): Node;
-    export function skipParentheses(node: Node): Node {
-        return skipOuterExpressions(node, OuterExpressionKinds.Parentheses);
+    export function skipParentheses(node: Expression, excludeJSDocTypeAssertions?: boolean): Expression;
+    export function skipParentheses(node: Node, excludeJSDocTypeAssertions?: boolean): Node;
+    export function skipParentheses(node: Node, excludeJSDocTypeAssertions?: boolean): Node {
+        const flags = excludeJSDocTypeAssertions ?
+            OuterExpressionKinds.Parentheses | OuterExpressionKinds.ExcludeJSDocTypeAssertion :
+            OuterExpressionKinds.Parentheses;
+        return skipOuterExpressions(node, flags);
     }
 
     // a node is delete target iff. it is PropertyAccessExpression/ElementAccessExpression with parentheses skipped

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -3218,7 +3218,8 @@ declare namespace ts {
         NonNullAssertions = 4,
         PartiallyEmittedExpressions = 8,
         Assertions = 6,
-        All = 15
+        All = 15,
+        ExcludeJSDocTypeAssertion = 16
     }
     export type TypeOfTag = "undefined" | "number" | "bigint" | "boolean" | "string" | "symbol" | "object" | "function";
     export interface NodeFactory {

tests/baselines/reference/api/typescript.d.ts

@@ -3218,7 +3218,8 @@ declare namespace ts {
         NonNullAssertions = 4,
         PartiallyEmittedExpressions = 8,
         Assertions = 6,
-        All = 15
+        All = 15,
+        ExcludeJSDocTypeAssertion = 16
     }
     export type TypeOfTag = "undefined" | "number" | "bigint" | "boolean" | "string" | "symbol" | "object" | "function";
     export interface NodeFactory {

tests/baselines/reference/jsdocTypeTagCast.errors.txt

@@ -123,4 +123,7 @@ tests/cases/conformance/jsdoc/b.js(67,8): error TS2454: Variable 'numOrStr' is u
     }
 
 
-    
+    var asConst1 = /** @type {const} */(1);
+    var asConst2 = /** @type {const} */({
+        x: 1
+    });

tests/baselines/reference/jsdocTypeTagCast.js

@@ -74,7 +74,10 @@ if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
 }
 
 
-
+var asConst1 = /** @type {const} */(1);
+var asConst2 = /** @type {const} */({
+    x: 1
+});
 
 //// [a.js]
 var W;
@@ -154,3 +157,7 @@ var str;
 if ( /** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
     str = numOrStr; // Error, no narrowing occurred
 }
+var asConst1 = /** @type {const} */ (1);
+var asConst2 = /** @type {const} */ ({
+    x: 1
+});

tests/baselines/reference/jsdocTypeTagCast.symbols

@@ -157,4 +157,13 @@ if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
 }
 
 
+var asConst1 = /** @type {const} */(1);
+>asConst1 : Symbol(asConst1, Decl(b.js, 70, 3))
 
+var asConst2 = /** @type {const} */({
+>asConst2 : Symbol(asConst2, Decl(b.js, 71, 3))
+
+    x: 1
+>x : Symbol(x, Decl(b.js, 71, 37))
+
+});

tests/baselines/reference/jsdocTypeTagCast.types

@@ -209,4 +209,18 @@ if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
 }
 
 
+var asConst1 = /** @type {const} */(1);
+>asConst1 : 1
+>(1) : 1
+>1 : 1
 
+var asConst2 = /** @type {const} */({
+>asConst2 : { readonly x: 1; }
+>({    x: 1}) : { readonly x: 1; }
+>{    x: 1} : { readonly x: 1; }
+
+    x: 1
+>x : 1
+>1 : 1
+
+});

tests/cases/conformance/jsdoc/jsdocTypeTagCast.ts

@@ -76,3 +76,7 @@ if(/** @type {numOrStr is string} */(numOrStr === undefined)) { // Error
 }
 
 
+var asConst1 = /** @type {const} */(1);
+var asConst2 = /** @type {const} */({
+    x: 1
+});