gopls/internal/analysis/simplifyrange: reenable on range-over-func

This reverts the functional change of commit 3629652 (CL 588056) that caused
range-over-func to differ from other range operands; but we keep some tests
and tidy up the logic.

It was decided at the 11th hour to permit redundant blanks in range-over-func
statements in the go1.23 spec; see
golang/go#65236 (comment).

Fixes golang/go#67239
Updates golang/go#65236

Change-Id: Ib3c1c535a1107a05f18732e07d7c8844bbac4d1e
Reviewed-on: https://go-review.googlesource.com/c/tools/+/594555
Reviewed-by: Robert Findley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: adonovan

gopls/internal/analysis/simplifyrange/simplifyrange.go

@@ -10,7 +10,6 @@ import (
 	"go/ast"
 	"go/printer"
 	"go/token"
-	"go/types"
 
 	"golang.org/x/tools/go/analysis"
 	"golang.org/x/tools/go/analysis/passes/inspect"
@@ -35,16 +34,12 @@ func run(pass *analysis.Pass) (interface{}, error) {
 		(*ast.RangeStmt)(nil),
 	}
 	inspect.Preorder(nodeFilter, func(n ast.Node) {
-		stmt := n.(*ast.RangeStmt)
-
-		// go1.23's range-over-func requires all vars, blank if necessary.
-		// TODO(adonovan): this may change in go1.24; see #65236.
-		if _, ok := pass.TypesInfo.TypeOf(stmt.X).Underlying().(*types.Signature); ok {
-			return
+		var copy *ast.RangeStmt // shallow-copy the AST before modifying
+		{
+			x := *n.(*ast.RangeStmt)
+			copy = &x
 		}
-
-		copy := *stmt
-		end := newlineIndex(pass.Fset, &copy)
+		end := newlineIndex(pass.Fset, copy)
 
 		// Range statements of the form: for i, _ := range x {}
 		var old ast.Expr
@@ -65,7 +60,7 @@ func run(pass *analysis.Pass) (interface{}, error) {
 			Pos:            old.Pos(),
 			End:            old.End(),
 			Message:        "simplify range expression",
-			SuggestedFixes: suggestedFixes(pass.Fset, &copy, end),
+			SuggestedFixes: suggestedFixes(pass.Fset, copy, end),
 		})
 	})
 	return nil, nil

gopls/internal/analysis/simplifyrange/simplifyrange_test.go

@@ -16,7 +16,7 @@ import (
 func Test(t *testing.T) {
 	testdata := analysistest.TestData()
 	analysistest.RunWithSuggestedFixes(t, testdata, simplifyrange.Analyzer, "a")
-	if slices.Contains(build.Default.ReleaseTags, "go1.23") {
+	if slices.Contains(build.Default.ReleaseTags, "go1.23") { // uses iter.Seq
 		analysistest.RunWithSuggestedFixes(t, testdata, simplifyrange.Analyzer, "rangeoverfunc")
 	}
 }

gopls/internal/analysis/simplifyrange/testdata/src/rangeoverfunc/rangeoverfunc.go

@@ -7,15 +7,14 @@ package testdata
 import "iter"
 
 func _(seq1 iter.Seq[int], seq2 iter.Seq2[int, int]) {
+	// range-over-func is (once again) consistent with other types (#65236)
 	for _ = range "" { // want "simplify range expression"
 	}
-
-	// silence
-	for _ = range seq1 {
+	for _ = range seq1 { // want `simplify range expression`
 	}
-	for _, v := range seq2 {
+	for _, v := range seq2 { // silence
 		_ = v
 	}
-	for _, _ = range seq2 {
+	for _, _ = range seq2 { // want `simplify range expression`
 	}
 }

gopls/internal/analysis/simplifyrange/testdata/src/rangeoverfunc/rangeoverfunc.go.golden

@@ -7,15 +7,14 @@ package testdata
 import "iter"
 
 func _(seq1 iter.Seq[int], seq2 iter.Seq2[int, int]) {
+	// range-over-func is (once again) consistent with other types (#65236)
 	for range "" { // want "simplify range expression"
 	}
-
-	// silence
-	for _ = range seq1 {
+	for range seq1 { // want `simplify range expression`
 	}
-	for _, v := range seq2 {
+	for _, v := range seq2 { // silence
 		_ = v
 	}
-	for _, _ = range seq2 {
+	for range seq2 { // want `simplify range expression`
 	}
 }