Don't store @template constraint in a TypeParameterDeclaration node

src/compiler/checker.ts

@@ -5948,7 +5948,8 @@ namespace ts {
 
         /** A type parameter is thisless if its contraint is thisless, or if it has no constraint. */
         function isThislessTypeParameter(node: TypeParameterDeclaration) {
-            return !node.constraint || isThislessType(node.constraint);
+            const constraint = getEffectiveConstraintOfTypeParameter(node);
+            return !constraint || isThislessType(constraint);
         }
 
         /**
@@ -6735,7 +6736,7 @@ namespace ts {
         }
 
         function getConstraintDeclarationForMappedType(type: MappedType) {
-            return type.declaration.typeParameter.constraint;
+            return getEffectiveConstraintOfTypeParameter(type.declaration.typeParameter);
         }
 
         function isMappedTypeWithKeyofConstraintDeclaration(type: MappedType) {
@@ -7872,7 +7873,7 @@ namespace ts {
 
         function getConstraintDeclaration(type: TypeParameter) {
             const decl = type.symbol && getDeclarationOfKind<TypeParameterDeclaration>(type.symbol, SyntaxKind.TypeParameter);
-            return decl && decl.constraint;
+            return decl && getEffectiveConstraintOfTypeParameter(decl);
         }
 
         function getInferredTypeParameterConstraint(typeParameter: TypeParameter) {
@@ -7936,7 +7937,9 @@ namespace ts {
         }
 
         function getParentSymbolOfTypeParameter(typeParameter: TypeParameter): Symbol | undefined {
-            return getSymbolOfNode(getDeclarationOfKind(typeParameter.symbol, SyntaxKind.TypeParameter)!.parent);
+            const tp = getDeclarationOfKind<TypeParameterDeclaration>(typeParameter.symbol, SyntaxKind.TypeParameter)!;
+            const host = isJSDocTemplateTag(tp.parent) ? getHostSignatureFromJSDoc(tp.parent) : tp.parent;
+            return host && getSymbolOfNode(host);
         }
 
         function getTypeListId(types: ReadonlyArray<Type> | undefined) {
@@ -22016,7 +22019,7 @@ namespace ts {
             checkSourceElement(node.default);
             const typeParameter = getDeclaredTypeOfTypeParameter(getSymbolOfNode(node));
             if (!hasNonCircularBaseConstraint(typeParameter)) {
-                error(node.constraint, Diagnostics.Type_parameter_0_has_a_circular_constraint, typeToString(typeParameter));
+                error(getEffectiveConstraintOfTypeParameter(node), Diagnostics.Type_parameter_0_has_a_circular_constraint, typeToString(typeParameter));
             }
             if (!hasNonCircularTypeParameterDefault(typeParameter)) {
                 error(node.default, Diagnostics.Type_parameter_0_has_a_circular_default, typeToString(typeParameter));
@@ -22749,7 +22752,7 @@ namespace ts {
 
             const type = <MappedType>getTypeFromMappedTypeNode(node);
             const constraintType = getConstraintTypeFromMappedType(type);
-            checkTypeAssignableTo(constraintType, keyofConstraintType, node.typeParameter.constraint);
+            checkTypeAssignableTo(constraintType, keyofConstraintType, getEffectiveConstraintOfTypeParameter(node.typeParameter));
         }
 
         function checkThisType(node: ThisTypeNode) {
@@ -23640,6 +23643,13 @@ namespace ts {
             checkSourceElement(node.typeExpression);
         }
 
+        function checkJSDocTemplateTag(node: JSDocTemplateTag): void {
+            checkSourceElement(node.constraint);
+            for (const tp of node.typeParameters) {
+                checkSourceElement(tp);
+            }
+        }
+
         function checkJSDocTypeTag(node: JSDocTypeTag) {
             checkSourceElement(node.typeExpression);
         }
@@ -25427,7 +25437,8 @@ namespace ts {
 
                     // If the type parameter node does not have an identical constraint as the resolved
                     // type parameter at this position, we report an error.
-                    const sourceConstraint = source.constraint && getTypeFromTypeNode(source.constraint);
+                    const constraint = getEffectiveConstraintOfTypeParameter(source);
+                    const sourceConstraint = constraint && getTypeFromTypeNode(constraint);
                     const targetConstraint = getConstraintOfTypeParameter(target);
                     if (sourceConstraint) {
                         // relax check if later interface augmentation has no constraint
@@ -26647,6 +26658,8 @@ namespace ts {
                 case SyntaxKind.JSDocTypedefTag:
                 case SyntaxKind.JSDocCallbackTag:
                     return checkJSDocTypeAliasTag(node as JSDocTypedefTag);
+                case SyntaxKind.JSDocTemplateTag:
+                    return checkJSDocTemplateTag(node as JSDocTemplateTag);
                 case SyntaxKind.JSDocTypeTag:
                     return checkJSDocTypeTag(node as JSDocTypeTag);
                 case SyntaxKind.JSDocParameterTag:
@@ -29763,6 +29776,13 @@ namespace ts {
             }
             return false;
         }
+
+        function getEffectiveConstraintOfTypeParameter(node: TypeParameterDeclaration): TypeNode | undefined {
+            return node.constraint ? node.constraint
+                : isJSDocTemplateTag(node.parent) && node === node.parent.typeParameters[0]
+                ? node.parent.constraint
+                : undefined;
+        }
     }
 
     /** Like 'isDeclarationName', but returns true for LHS of `import { x as y }` or `export { x as y }`. */

src/compiler/parser.ts

@@ -475,7 +475,7 @@ namespace ts {
             case SyntaxKind.JSDocAugmentsTag:
                 return visitNode(cbNode, (<JSDocAugmentsTag>node).class);
             case SyntaxKind.JSDocTemplateTag:
-                return visitNodes(cbNode, cbNodes, (<JSDocTemplateTag>node).typeParameters);
+                return visitNode(cbNode, (<JSDocTemplateTag>node).constraint) || visitNodes(cbNode, cbNodes, (<JSDocTemplateTag>node).typeParameters);
             case SyntaxKind.JSDocTypedefTag:
                 if ((node as JSDocTypedefTag).typeExpression &&
                     (node as JSDocTypedefTag).typeExpression!.kind === SyntaxKind.JSDocTypeExpression) {
@@ -7049,13 +7049,10 @@ namespace ts {
                         typeParameters.push(typeParameter);
                     } while (parseOptionalJsdoc(SyntaxKind.CommaToken));
 
-                    if (constraint) {
-                        first(typeParameters).constraint = constraint.type;
-                    }
-
                     const result = <JSDocTemplateTag>createNode(SyntaxKind.JSDocTemplateTag, atToken.pos);
                     result.atToken = atToken;
                     result.tagName = tagName;
+                    result.constraint = constraint;
                     result.typeParameters = createNodeArray(typeParameters, typeParametersPos);
                     finishNode(result);
                     return result;

src/compiler/types.ts

@@ -759,6 +759,7 @@ namespace ts {
         kind: SyntaxKind.TypeParameter;
         parent: DeclarationWithTypeParameterChildren | InferTypeNode;
         name: Identifier;
+        // Note: Consider calling `getEffectiveConstraintOfTypeParameter`
         constraint?: TypeNode;
         default?: TypeNode;
 
@@ -2363,6 +2364,7 @@ namespace ts {
 
     export interface JSDocTemplateTag extends JSDocTag {
         kind: SyntaxKind.JSDocTemplateTag;
+        constraint: TypeNode | undefined;
         typeParameters: NodeArray<TypeParameterDeclaration>;
     }
 

src/compiler/utilities.ts

@@ -1016,6 +1016,8 @@ namespace ts {
                         return !isExpressionWithTypeArgumentsInClassExtendsClause(parent);
                     case SyntaxKind.TypeParameter:
                         return node === (<TypeParameterDeclaration>parent).constraint;
+                    case SyntaxKind.JSDocTemplateTag:
+                        return node === (<JSDocTemplateTag>parent).constraint;
                     case SyntaxKind.PropertyDeclaration:
                     case SyntaxKind.PropertySignature:
                     case SyntaxKind.Parameter:

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

@@ -1568,6 +1568,7 @@ declare namespace ts {
     }
     interface JSDocTemplateTag extends JSDocTag {
         kind: SyntaxKind.JSDocTemplateTag;
+        constraint: TypeNode | undefined;
         typeParameters: NodeArray<TypeParameterDeclaration>;
     }
     interface JSDocReturnTag extends JSDocTag {

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

@@ -1568,6 +1568,7 @@ declare namespace ts {
     }
     interface JSDocTemplateTag extends JSDocTag {
         kind: SyntaxKind.JSDocTemplateTag;
+        constraint: TypeNode | undefined;
         typeParameters: NodeArray<TypeParameterDeclaration>;
     }
     interface JSDocReturnTag extends JSDocTag {

tests/baselines/reference/jsdocTemplateTag3.errors.txt

@@ -2,10 +2,11 @@ tests/cases/conformance/jsdoc/a.js(14,29): error TS2339: Property 'a' does not e
 tests/cases/conformance/jsdoc/a.js(14,35): error TS2339: Property 'b' does not exist on type 'U'.
 tests/cases/conformance/jsdoc/a.js(21,3): error TS2345: Argument of type '{ a: number; }' is not assignable to parameter of type '{ a: number; b: string; }'.
   Property 'b' is missing in type '{ a: number; }'.
+tests/cases/conformance/jsdoc/a.js(24,15): error TS2304: Cannot find name 'NoLongerAllowed'.
 tests/cases/conformance/jsdoc/a.js(25,2): error TS1069: Unexpected token. A type parameter name was expected without curly braces.
 
 
-==== tests/cases/conformance/jsdoc/a.js (4 errors) ====
+==== tests/cases/conformance/jsdoc/a.js (5 errors) ====
     /**
      * @template {{ a: number, b: string }} T,U A Comment
      * @template {{ c: boolean }} V uh ... are comments even supported??
@@ -37,6 +38,8 @@ tests/cases/conformance/jsdoc/a.js(25,2): error TS1069: Unexpected token. A type
 
     /**
      * @template {NoLongerAllowed}
+                  ~~~~~~~~~~~~~~~
+!!! error TS2304: Cannot find name 'NoLongerAllowed'.
      * @template T preceding line's syntax is no longer allowed
      ~
 !!! error TS1069: Unexpected token. A type parameter name was expected without curly braces.

tests/cases/fourslash/editTemplateConstraint.ts

@@ -0,0 +1,10 @@
+/// <reference path='fourslash.ts' />
+
+/////**
+//// * @template {/**/
+//// */
+////function f() {}
+
+goTo.marker("");
+edit.insert("n");
+edit.insert("u");

tests/cases/fourslash/quickInfoTemplateTag.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts'/>
+
+// @allowJs: true
+// @checkJs: true
+// @Filename: /foo.js
+
+/////**
+//// * Doc
+//// * @template {new (...args: any[]) => any} T
+//// * @param {T} cls
+//// */
+////function /**/myMixin(cls) {
+////    return class extends cls {}
+////}
+
+verify.quickInfoAt("",
+`function myMixin<T extends new (...args: any[]) => any>(cls: T): {
+    new (...args: any[]): (Anonymous class);
+    prototype: myMixin<any>.(Anonymous class);
+} & T`,
+"Doc");