x/tools: fix remaining places in preparation for new(expr)

+ tests

For golang/go#45624

Change-Id: Idb5b0a78f9af9230abffe0282087ac50494d967f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/706255
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: adonovan

go/analysis/passes/copylock/copylock.go

@@ -157,7 +157,10 @@ func checkCopyLocksCallExpr(pass *analysis.Pass, ce *ast.CallExpr) {
 	}
 	if fun, ok := pass.TypesInfo.Uses[id].(*types.Builtin); ok {
 		switch fun.Name() {
-		case "new", "len", "cap", "Sizeof", "Offsetof", "Alignof":
+		case "len", "cap", "Sizeof", "Offsetof", "Alignof":
+			// The argument of this operation is used only
+			// for its type (e.g. len(array)), or the operation
+			// does not copy a lock (e.g. len(slice)).
 			return
 		}
 	}

go/analysis/passes/copylock/copylock_test.go

@@ -10,7 +10,6 @@ import (
 
 	"golang.org/x/tools/go/analysis/analysistest"
 	"golang.org/x/tools/go/analysis/passes/copylock"
-	"golang.org/x/tools/internal/testenv"
 	"golang.org/x/tools/internal/testfiles"
 )
 
@@ -20,8 +19,6 @@ func Test(t *testing.T) {
 }
 
 func TestVersions22(t *testing.T) {
-	testenv.NeedsGo1Point(t, 22)
-
 	dir := testfiles.ExtractTxtarFileToTmp(t, filepath.Join(analysistest.TestData(), "src", "forstmt", "go22.txtar"))
 	analysistest.Run(t, dir, copylock.Analyzer, "golang.org/fake/forstmt")
 }

go/analysis/passes/copylock/testdata/src/a/newexpr_go126.go

@@ -0,0 +1,14 @@
+// Copyright 2025 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 go1.26
+
+package a
+
+import "sync"
+
+func _(ptr *sync.Mutex) {
+	_ = new(sync.Mutex)
+	_ = new(*ptr) // want `call of new copies lock value: sync.Mutex`
+)

refactor/satisfy/find.go

@@ -204,8 +204,10 @@ func (f *Finder) call(sig *types.Signature, args []ast.Expr) {
 func (f *Finder) builtin(obj *types.Builtin, sig *types.Signature, args []ast.Expr) {
 	switch obj.Name() {
 	case "make", "new":
-		// skip the type operand
-		for _, arg := range args[1:] {
+		for i, arg := range args {
+			if i == 0 && f.info.Types[arg].IsType() {
+				continue // skip the type operand
+			}
 			f.expr(arg)
 		}
 

refactor/satisfy/find_test.go

@@ -15,6 +15,7 @@ import (
 	"sort"
 	"testing"
 
+	"golang.org/x/tools/internal/testenv"
 	"golang.org/x/tools/refactor/satisfy"
 )
 
@@ -204,6 +205,25 @@ func _[P ~struct{F I}]() {
 	}
 }
 
+func TestNewExpr(t *testing.T) {
+	testenv.NeedsGo1Point(t, 26)
+	const src = `package p
+
+type I interface{ f() }
+type C int
+func (C) f() {}
+
+var _ I = new(C(123))
+`
+	got := constraints(t, src)
+	want := []string{
+		"p.I <- *p.C",
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("found unexpected constraints: got %s, want %s", got, want)
+	}
+}
+
 func constraints(t *testing.T, src string) []string {
 	// parse
 	fset := token.NewFileSet()