Skip trivia after '<' in type-argument arity error spans

[Copilot]

The TS2558 Expected N type arguments diagnostic (and related arity diagnostics) underlined the whitespace/newlines after <, because the span started at TypeArgumentList().Loc, which begins immediately after the < token. TypeScript instead skips trivia, so the span starts at the first type argument.

Given:

declare function f<T>(a: T): T;

f<   string, number>("a");

the error now underlines string, number (matching typescript@6.0) instead of string, number, and the multi-line variant points at the line containing the first argument rather than the line with f<.

Changes

• internal/checker/checker.go — getTypeArgumentArityError computes the span as skipTrivia(text, typeArgs.Pos())..typeArgs.End(), covering the single-signature, overload-range, and overload single-count diagnostics.
• internal/checker/jsx.go — Same trivia-skip applied to the JSX intrinsic "Expected 0 type arguments" diagnostic, which shares the message and pattern.
• testdata/.../typeArgumentArityErrorSkipsTrivia.ts — New compiler test + baselines covering single-line and multi-line trivia after <.

[Copilot]

Pull request overview

This PR aligns TypeScript-Go’s TS2558 (and related type-argument arity) diagnostic spans with upstream TypeScript behavior by skipping trivia immediately after the < token, so underlines start at the first type argument rather than including whitespace/newlines.

Changes:

• Update getTypeArgumentArityError to compute a trivia-skipped diagnostic span for type-argument arity errors (single-signature and overload cases).
• Apply the same span adjustment to the JSX intrinsic-element “Expected 0 type arguments” diagnostic.
• Add a new compiler regression test (with baselines) covering single-line and multi-line whitespace/newline trivia after <.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

File	Description
internal/checker/checker.go	Adjust TS2558/overload arity diagnostic span to start at SkipTrivia(...) instead of the raw type-argument-list start.
internal/checker/jsx.go	Adjust JSX intrinsic “Expected 0 type arguments” diagnostic span to skip trivia after <.
testdata/tests/cases/compiler/typeArgumentArityErrorSkipsTrivia.ts	New regression test for trivia-skipping in type-argument arity diagnostics.
testdata/baselines/reference/compiler/typeArgumentArityErrorSkipsTrivia.*	New baselines validating the updated diagnostic span behavior.

[Copilot]

Addressed in 54f90e9 by adding a local compiler regression test for both <div< number> /> and the multi-line <div<\n number> /> cases, along with the updated baselines.