Fix panic when @this JSDoc tag is combined with a literal this parameter

[Copilot]

tsgo panics on /** @this {object} */ function f(this) {} because the reparser fails to detect the existing this parameter and prepends a duplicate synthetic one, producing a diagnostic with position -1.

The check params[0].Name().Kind != ast.KindThisKeyword misses the case where the parser creates the this parameter name as a KindIdentifier with text "this" (via createIdentifier), not as a KindThisKeyword node.

• Added ast.IsThisIdentifier() check to the existing condition in reparseHosted to cover both node kinds
• Added compiler test case jsdocThisTagWithThisParameter

[Copilot]

Pull request overview

Prevents a tsgo panic when a @this JSDoc tag appears on a function that already has a literal this parameter whose name node is represented as an Identifier("this") rather than a ThisKeyword, by ensuring the reparser recognizes both forms and avoids prepending a duplicate synthetic this parameter. Adds a compiler regression test and reference baselines to lock in the non-crashing behavior and diagnostics.

Changes:

• Teach Parser.reparseHosted’s JSDocThisTag handling to treat Identifier("this") as an existing this parameter (via ast.IsThisIdentifier), not just KindThisKeyword.
• Add a new compiler test case covering /** @this {object} */ function f(this) {} under checkJs.
• Add reference baselines (.types, .symbols, .errors.txt) for the new test.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
internal/parser/reparser.go	Avoids inserting a duplicate synthetic this parameter by also recognizing Identifier("this") names.
testdata/tests/cases/compiler/jsdocThisTagWithThisParameter.ts	New regression test reproducing the crash scenario in a JS file under checkJs.
testdata/baselines/reference/compiler/jsdocThisTagWithThisParameter.types	Records expected type output for the new test.
testdata/baselines/reference/compiler/jsdocThisTagWithThisParameter.symbols	Records expected symbol output for the new test.
testdata/baselines/reference/compiler/jsdocThisTagWithThisParameter.errors.txt	Records expected diagnostic output for the new test.