Handle constraints on type params in JS classes

resolves #2929

Author: Gerrit0

CHANGELOG.md

@@ -21,6 +21,7 @@ title: Changelog
 - Inlining types can now handle more type variants, #2920.
 - Fixed behavior of `externalSymbolLinkMappings` option when URL is set to `#`, #2921.
 - Fixed broken links within module pages when structure-dir router was used, #2928.
+- Type parameters on JS classes defined with `@typedef` now correctly handle the constraint, #2929.
 - API: `toString` on types containing index signatures now behave correctly, #2917.
 
 ## v0.28.1 (2025-03-20)

src/lib/converter/comments/index.ts

@@ -374,10 +374,15 @@ export function getJsDocComment(
     const tag = comment.getIdentifiedTag(name, `@${declaration.tagName.text}`);
 
     if (!tag) {
-        logger.error(
-            i18n.failed_to_find_jsdoc_tag_for_name_0(name),
-            declaration,
-        );
+        // If this is a template tag with multiple declarations, we warned already if there
+        // was a comment attached. If there wasn't, then don't error about failing to find
+        // a tag because this is unsupported.
+        if (!ts.isJSDocTemplateTag(declaration)) {
+            logger.error(
+                i18n.failed_to_find_jsdoc_tag_for_name_0(name),
+                declaration,
+            );
+        }
     } else {
         const result = new Comment(Comment.cloneDisplayParts(tag.content));
         result.sourcePath = comment.sourcePath;

src/lib/converter/factories/signature.ts

@@ -453,12 +453,23 @@ export function createTypeParamReflection(
         getVariance(param.modifiers),
     );
     const paramScope = context.withScope(paramRefl);
-    paramRefl.type = param.constraint
-        ? context.converter.convertType(paramScope, param.constraint)
-        : void 0;
+
+    if (ts.isJSDocTemplateTag(param.parent)) {
+        // With a @template tag, the constraint applies only to the
+        // first type parameter declared.
+        if (param.parent.typeParameters[0].name.text === param.name.text && param.parent.constraint) {
+            paramRefl.type = context.converter.convertType(paramScope, param.parent.constraint);
+        }
+    } else {
+        paramRefl.type = param.constraint
+            ? context.converter.convertType(paramScope, param.constraint)
+            : void 0;
+    }
+
     paramRefl.default = param.default
         ? context.converter.convertType(paramScope, param.default)
         : void 0;
+
     if (param.modifiers?.some((m) => m.kind === ts.SyntaxKind.ConstKeyword)) {
         paramRefl.flags.setFlag(ReflectionFlag.Const, true);
     }

src/test/converter2/issues/gh2929.js

@@ -0,0 +1,15 @@
+/**
+ * @template {number} [T=1]
+ */
+export class NumberManager {
+    /**
+     * @param {T[]} nums
+     */
+    constructor(nums) {}
+}
+
+/**
+ * @template {number} A, B
+ */
+export class EdgeCases {
+}

src/test/issues.c2.test.ts

@@ -2099,4 +2099,14 @@ describe("Issue Tests", () => {
         const test3 = query(project, "InlineArray");
         equal(test3.type?.toString(), "string[]");
     });
+
+    it("#2929 handles type parameters on JS classes", () => {
+        const project = convert();
+        const NumberManager = query(project, "NumberManager");
+        equal(NumberManager.typeParameters?.map(t => t.type?.toString()), ["number"]);
+        equal(NumberManager.typeParameters?.map(t => t.default?.toString()), ["1"]);
+
+        const EdgeCases = query(project, "EdgeCases");
+        equal(EdgeCases.typeParameters?.map(t => t.type?.toString()), ["number", undefined]);
+    });
 });