Consistently use len(x) != 0 checks for Signature.typeParameters

[ahejlsberg]

Fixes #1442.

[Copilot]

Pull Request Overview

This PR standardizes the way signature type parameters are checked throughout the codebase by consistently using len(x.typeParameters) != 0 instead of x.typeParameters != nil. This change improves code consistency and likely fixes edge cases where empty slices were being treated differently from nil slices.

• Replaces nil checks with length checks for signature type parameters across multiple files
• Updates test baselines to reflect improved error messages and type inference behavior
• Ensures consistent handling of generic signatures throughout the type checker

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/checker/relater.go	Updates signature comparison and type predicate logic to use length checks
internal/checker/nodebuilderimpl.go	Modifies signature declaration helper to use length checks and simplifies conditional logic
internal/checker/flow.go	Updates effects signature detection to use length checks
internal/checker/checker.go	Converts multiple signature type parameter checks from nil to length-based
testdata/baselines/reference/submodule/compiler/jsxComponentTypeErrors.errors.txt*	Updates test baselines showing improved JSX error messages
testdata/baselines/reference/submodule/compiler/abstractClassUnionInstantiation.types*	Updates test baselines showing improved union type inference

[ahejlsberg]

We already have a couple of failing tests that this fixes, so don't think we need additional tests.

[Eigilak]

Altid en fornøjelse jo! 🙌