go/parser: avoid formatting a panic message if an assertion succeeds
tryResolve is an extremely hot method on the parser. Eliminating this
formatting led to a 20% performance improvement in BenchmarkParse.
Change-Id: Idf8850404bd72d45d1351356427a85086422ea68
Reviewed-on: https://go-review.googlesource.com/c/go/+/302629
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>