Fix JSDoc inheritance for overridden methods and properties in hover

[Copilot]

Overridden methods and properties in derived classes/interfaces were not showing JSDoc comments from their base declarations on hover.

interface Base {
  /** Documentation here */
  method(): void;
}

interface Derived extends Base {
  method(): void;  // Hover showed no docs
}

Changes

• internal/ls/hover.go: Added getJSDocFromBaseTypes() to recursively search base types for JSDoc when current declaration lacks documentation. Modified getDocumentationFromDeclaration() to accept symbol parameter and invoke base type search.

• internal/checker/exports.go: Exported GetBaseTypes() to enable base type traversal in language service.

• Tests: Added hoverInheritedJSDoc_test.go covering interface extension and class inheritance scenarios. Updated baselines for existing JSDoc inheritance tests to reflect correct behavior.

The fix handles multiple inheritance levels and includes nil safety for non-class/interface types (enums, modules, etc.).

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Classes and interfaces lose hover JSDoc comments from parent class/interface when re-declaring properties</issue_title>
<issue_description>### Extension Version

v0.20251107.1

VS Code Version

1.105.1

Operating system Version

Ubuntu x86-64 (WSL, though I highly doubt this matters)

Steps to reproduce

Copy the following MRE into a new .ts file in the editor.

interface foo {
  /** base jsdoc */
  bar(k: string): number;
  /** other jsdoc */
  other: 24;
}

interface bar extends foo {
  bar(k: string | symbol): number | 99;
}

declare class thing {
  /** doc comment */
  method(s: string): void;
}

declare class potato extends thing {
  method(s: "1234"): void;
}

declare const f: foo;
declare const b: bar;
declare const t: thing;
declare const p: potato;

// b and p lack comments on the properties they overrode (`bar` and `method` respectively)
f.bar;
f.other;
b.bar;
b.other;
t.method;
p.method;

Hover over the bottom 6 symbols and notice how b and p's overridden methods lack hover comments.

Issue

The interfaces and classes should inherit the parents' doc comments if they themself lack an accompanying JSDoc comment, as happens with normal tsc.

NB: This also occurs with classes implementing interfaces and interfaces extending classes.</issue_description>

<agent_instructions>Use fourslash tests for this, in ./internal/fourslash/tests; there are examples of hover there.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Classes and interfaces lose hover JSDoc comments from parent class/interface when re-declaring properties #2035

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[jakebailey]

@copilot This function does not exist in the old codebase. What does this code correspond to?

[Copilot]

This corresponds to the findBaseOfDeclaration function in src/services/services.ts (lines ~3565-3575 in the TypeScript codebase).

The TypeScript implementation:

function findBaseOfDeclaration<T>(checker: TypeChecker, declaration: Declaration, cb: (symbol: Symbol) => T[] | undefined): T[] | undefined {
    const classOrInterfaceDeclaration = declaration.parent?.kind === SyntaxKind.Constructor ? declaration.parent.parent : declaration.parent;
    if (!classOrInterfaceDeclaration) return;

    const isStaticMember = hasStaticModifier(declaration);
    return firstDefined(getAllSuperTypeNodes(classOrInterfaceDeclaration), superTypeNode => {
        const baseType = checker.getTypeAtLocation(superTypeNode);
        const type = isStaticMember && baseType.symbol ? checker.getTypeOfSymbol(baseType.symbol) : baseType;
        const symbol = checker.getPropertyOfType(type, declaration.symbol.name);
        return symbol ? cb(symbol) : undefined;
    });
}

Our Go implementation achieves the same goal: traverse base types to find JSDoc from parent declarations when the current declaration lacks documentation.