go/parser: ast.File.File{Start,End} fields are uninitialized when parser bails out early

[adonovan]

When the parser fails to parse even the package declaration, it bails out early, returning a nil *ast.File. The calling code has a deferred function that replaces this nil with a mininally valid ast.File... except that it fails to populate the FileStart and FileEnd fields (my bad).

Example: https://go.dev/play/p/KtgnRPdgyPE

We should populate these fields in all cases:

		FileStart: token.Pos(p.file.Base()),
		FileEnd:   token.Pos(p.file.Base() + p.file.Size()),

I will send a CL.

[gabyhelp]

Related Issues and Documentation

• go/ast: record start and end of file in File.FileStart, File.FileEnd #53202 (closed)

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[gopherbot]

Change https://go.dev/cl/624437 mentions this issue: x/tools: fset.File(file.Pos()) -> fset.File(file.FileStart)

[gopherbot]

Change https://go.dev/cl/624655 mentions this issue: go/parser: set File{Start,End} correctly in all cases

[gopherbot]

Change https://go.dev/cl/631675 mentions this issue: gopls/internal/golang: refine crash golang/go#70553