[TypeScript] Mapped Types with Template Literal Keys Do Not Preserve Type Declaration References

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.96.4 (Universal)
• OS Version: Darwin arm64 23.6.0 (macOS Sonoma 14.7.2)
• TypeScript Version: 5.7.3

When using Mapped Types with template literal transformations on interface fields, VSCode does not retain the original type reference. This makes it impossible to use “Go to Definition” to navigate from the transformed key back to its original declaration. WebStorm correctly maintains this reference, but VSCode does not.

Steps to Reproduce:

interface Source {
  alpha: number;
  beta: string;
}

// Transforming interface field names with a suffix
type Transformed<T> = {
  [K in keyof T as `${K & string}Suffix`]: () => T[K];
};

type Result = Transformed<Source>;
/*
Expected:
{
  alphaSuffix: () => number;
  betaSuffix: () => string;
}
*/

const obj: Result = {
  alphaSuffix: () => 42,
  betaSuffix: () => "hello",
};

// ❌ In VSCode, "Go to Definition" on `alphaSuffix` does not navigate to `alpha` in `Source`
obj.alphaSuffix();

Expected Behavior

• “Go to Definition” on alphaSuffix should navigate to alpha in Source.
• VSCode should retain the reference between transformed keys and their original interface field names.
• This works as expected in WebStorm, where alphaSuffix correctly links back to alpha.

Actual Behavior

• VSCode treats transformed keys as completely new identifiers, losing the connection to their original interface fields.
• “Go to Definition” does not work for mapped types with template literal keys.
• WebStorm successfully tracks the transformation and allows navigation to alpha.

使用 TypeScript 5.7.3 复现 mapped type 示例，并测试从 alphaSuffix 到 Source.alpha 的 Go to Definition。首先跟踪 TypeScript language service 对 mapped type 和模板字面量键的定义查找；完成的标准是转换后的键能够跳转到其原始接口字段，并且该行为有回归测试覆盖。