Fix symbol auto-import: prevent value symbols from being added to type-only imports

[Copilot]

This PR fixes an issue where symbols used in computed property access (obj[symbol]) were incorrectly added to existing type-only imports instead of creating separate value imports.

Problem

When auto-completing symbol properties on objects, TypeScript would incorrectly import symbols as types when there was already a type-only import from the same module:

// exportsSymbol.ts
export const SYM_FOO_BAR = Symbol.for("foo.bar");
export interface ObjWithSym {
    [SYM_FOO_BAR]: any;
}

// usesSymbol.ts
import type { ObjWithSym } from "./exportsSymbol";
declare const thing: ObjWithSym;

function main() {
    thing[SYM_FOO_BAR] // Auto-completing this would incorrectly add SYM_FOO_BAR to the type-only import
}

Before (incorrect):

import type { ObjWithSym, SYM_FOO_BAR } from "./exportsSymbol";

After (correct):

import type { ObjWithSym } from "./exportsSymbol";
import { SYM_FOO_BAR } from "./exportsSymbol";

Root Cause

The bug was in the tryAddToExistingImport function in src/services/codefixes/importFixes.ts. The logic gave preference to adding symbols to existing type-only imports even when the symbol needed to be imported as a value (like symbols used in computed property access).

Solution

Added a check to prevent value-only symbols (addAsTypeOnly === AddAsTypeOnly.NotAllowed) from being added to type-only imports. When such a symbol is encountered, the function now skips the type-only import and either finds a suitable value import or creates a new one.

Changes

• Fixed logic in tryAddToExistingImport: Added early continue when attempting to add value-only symbols to type-only imports
• Added test case: completionsSymbolTypeOnlyImportBug.ts to verify the fix and prevent regressions

The fix is minimal and targeted - it only affects the specific case where a value symbol would incorrectly be added to a type-only import, preserving all other existing behavior including the correct addition of types to type-only imports.

Fixes #61894.

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