go/ast: add func Unparen(Expr) Expr

[adonovan]

Almost every application that uses go/ast needs a function to strip parens. There are 4 copies of unparen in the standard library. golang.org/x/tools has astutil.Unparen. I propose we add this function to go/ast.

package ast // import "go/ast"

// Unparen returns e with any enclosing parentheses stripped.
func Unparen(e Expr) Expr

See https://go.dev/cl/495315 for the implementation.

[gopherbot]

Change https://go.dev/cl/495315 mentions this issue: go/ast: add Unparen(Expr) helper

[rsc]

Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group

[rsc]

No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group

[gopherbot]

Change https://go.dev/cl/548882 mentions this issue: doc/go1.22: document ast.Unparen

[gopherbot]

Change https://go.dev/cl/612038 mentions this issue: x/tools: deprecate astutil.Unparen