x/tools/gopls: gopls doesn't report some build errors

[ShoshinNikita]

• gopls version: v0.10.1 and master (f718365)
• go version: go1.19.2

gopls doesn't take into account private interface methods from std or third-party packages. It results in the absence of some build errors. For example, consider the following code:

-- main.go --
package main

import (
	"go/ast"
	"go/token"
)

func main() {
	var a int               // expected error: "a declared but not used"
	var _ ast.Expr = node{} // expected error: "cannot use node{} ... (missing exprNode method)"
}

type node struct{}

func (node) Pos() token.Pos { return 0 }
func (node) End() token.Pos { return 0 }

I expect to get 2 errors, but gopls reports only one:

$ go build main.go

# command-line-arguments
./main.go:9:6: a declared but not used
./main.go:10:19: cannot use node{} (value of type node) as type ast.Expr in variable declaration:
        node does not implement ast.Expr (missing exprNode method)

$ gopls check main.go

/tmp/main.go:9:6-7: a declared but not used

[findleyr]

Thanks, this is a problem with "parse exported" mode. We're working on replacing this with export data for the v0.11.0 milestone.