fix(extgen): better error handling

[dunglas]

Superseeds #2351.

Use errors.Join() to preserve all errors in extgen.

[alexandre-daubois]

I didn't know that. Thanks!

[Copilot]

Pull request overview

This PR updates the internal/extgen parsing pipeline to preserve both parsing/scanning errors and Close() errors by switching deferred file-closing logic to errors.Join(), and adjusts related tests’ temp-file cleanup assertions.

Changes:

• Replace deferred Close() error handling with errors.Join() in several extgen parsers.
• Remove fmt.Printf-based close-error logging (namespace parser) in favor of error propagation.
• Simplify test cleanup by using require.NoError for temp-file removal and removing an unused assert import.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/extgen/nsparser.go	Attempts to join Close() errors with existing errors (currently ineffective due to unnamed return / returning scanner.Err() directly).
internal/extgen/funcparser.go	Uses errors.Join() in deferred Close() to preserve both parse and close errors.
internal/extgen/constparser.go	Uses errors.Join() in deferred Close() to preserve both parse and close errors.
internal/extgen/classparser.go	Uses errors.Join() in deferred Close() to preserve both parse and close errors in method parsing.
internal/extgen/namespace_test.go	Uses require for cleanup and removes unused assert import.
internal/extgen/cfile_namespace_test.go	Uses require for cleanup in the temp-file test.

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