x/tools/go/analysis/internal/checker: support RunDespiteErrors

[adonovan]

The Go analysis framework allows an Analyzer to indicate that it is safe to run even in the presence of syntax and type errors, by setting RunDespiteErrors. However, the internal/checker package (used by {single,multi}checker) doesn't support it, as can be verified by running this main program:

go/analysis/passes/copylock/main.go

// Copyright 2024 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build ignore

// The copylock command applies the golang.org/x/tools/go/analysis/passes/copylock
// analysis to the specified packages of Go source code.
package main

import (
	"golang.org/x/tools/go/analysis/passes/copylock"
	"golang.org/x/tools/go/analysis/singlechecker"
)

func main() { singlechecker.Main(copylock.Analyzer) }

on the test case in #67787. The output is:

$ copylock -v ./...
-: # rsc.io/tmp/goplsbug
./x.go:8:31: T (type) is not an expression
./x.go:8:31: T (type) is not an expression
copylocks: 2 errors during loading

CL https://go.dev/cl/383974 purports to have added support for RunDespiteErrors, but the heuristic it uses to classify errors as typeParseError is evidently incorrect.

@zpavlinovic

[gopherbot]

Change https://go.dev/cl/591117 mentions this issue: internal/checker: run despite all errors