Add inlay hints for IndexSignature #56580
Conversation
…ranas/more-inlay-hints
typescript-bot
added
the
For Uncommitted Bug
| @@ -750,6 +751,17 @@ export function provideInlayHints(context: InlayHintsContext): InlayHint[] { | |||
| visitForDisplayParts(node.type); | |||
| } | |||
| break; | |||
| case SyntaxKind.IndexSignature: | |||
| Debug.assertNode(node, isIndexSignatureDeclaration); | |||
| Debug.assertEqual(node.parameters.length, 1); | |||
There was a problem hiding this comment.
I'm not sure if an assertion is appropriate - what happens if you have something like this?
const x: { []: string }
const y = x;There was a problem hiding this comment.
Specifically, assertions shouldn't assume well-formed code, they should assert invariants of how the compiler constructs the tree. You'd probably be better off with just visitParametersAndTypeParameters or node.parameters.forEach(visitForDisplayParts).
There was a problem hiding this comment.
I get An index signature must have exactly one parameter.ts(1096) for that code. Also, the parser doesn't create an index signature node for that (the type literal node just has no member children nodes) so this switch case isn't hit,
That being said, I also wasn't so enthusiastic about using the assert but wasn't sure about alternatives. Your suggestion is better though since this is a user error and we already report diagnostics to the user elsewhere.
I think this should be represented in the types though so we can enforce the invariant. Can we just add something like:
export interface IndexSignatureDeclaration extends SignatureDeclarationBase, ...
{
...
readonly parameters: [ParameterDeclaration] & NodeArray<ParameterDeclaration>;
}It's probably not that easy since this is a public API and would be breaking.
Fixes #56559