gopls/internal/analysis/modernize/slicesdelete: convert index type if needed

As go compiler has a rule "the index x must be an untyped constant or its core
type must be an integer" but slices.Delete accepts the int only, the compatible
index type may break type checking after applying modernize fix.

This CL checks whether the index type is int type, and converts it to int by
'int(expr)'.

Fixes golang/go#73663

Change-Id: I13553e8149baa290f8a0793ed5615481a1418919
Reviewed-on: https://go-review.googlesource.com/c/tools/+/671735
Reviewed-by: Alan Donovan <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: xieyuschen

gopls/internal/analysis/modernize/modernize.go

@@ -177,6 +177,7 @@ var (
 	builtinAny     = types.Universe.Lookup("any")
 	builtinAppend  = types.Universe.Lookup("append")
 	builtinBool    = types.Universe.Lookup("bool")
+	builtinInt     = types.Universe.Lookup("int")
 	builtinFalse   = types.Universe.Lookup("false")
 	builtinLen     = types.Universe.Lookup("len")
 	builtinMake    = types.Universe.Lookup("make")

gopls/internal/analysis/modernize/slicesdelete.go

@@ -45,7 +45,39 @@ func slicesdelete(pass *analysis.Pass) {
 	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	info := pass.TypesInfo
 	report := func(file *ast.File, call *ast.CallExpr, slice1, slice2 *ast.SliceExpr) {
+		insert := func(pos token.Pos, text string) analysis.TextEdit {
+			return analysis.TextEdit{Pos: pos, End: pos, NewText: []byte(text)}
+		}
+		isIntExpr := func(e ast.Expr) bool {
+			return types.Identical(types.Default(info.TypeOf(e)), builtinInt.Type())
+		}
+		isIntShadowed := func() bool {
+			scope := pass.TypesInfo.Scopes[file].Innermost(call.Lparen)
+			if _, obj := scope.LookupParent("int", call.Lparen); obj != builtinInt {
+				return true // int type is shadowed
+			}
+			return false
+		}
+
 		_, prefix, edits := analysisinternal.AddImport(info, file, "slices", "slices", "Delete", call.Pos())
+		// append's indices may be any integer type; slices.Delete requires int.
+		// Insert int conversions as needed (and if possible).
+		if isIntShadowed() && (!isIntExpr(slice1.High) || !isIntExpr(slice2.Low)) {
+			return
+		}
+		if !isIntExpr(slice1.High) {
+			edits = append(edits,
+				insert(slice1.High.Pos(), "int("),
+				insert(slice1.High.End(), ")"),
+			)
+		}
+		if !isIntExpr(slice2.Low) {
+			edits = append(edits,
+				insert(slice2.Low.Pos(), "int("),
+				insert(slice2.Low.End(), ")"),
+			)
+		}
+
 		pass.Report(analysis.Diagnostic{
 			Pos:      call.Pos(),
 			End:      call.End(),
@@ -123,7 +155,6 @@ func slicesdelete(pass *analysis.Pass) {
 // Given two slice indices a and b, returns true if we can verify that a < b.
 // It recognizes certain forms such as i+k1 < i+k2 where k1 < k2.
 func increasingSliceIndices(info *types.Info, a, b ast.Expr) bool {
-
 	// Given an expression of the form i±k, returns (i, k)
 	// where k is a signed constant. Otherwise it returns (e, 0).
 	split := func(e ast.Expr) (ast.Expr, constant.Value) {

gopls/internal/analysis/modernize/testdata/src/slicesdelete/slicesdelete.go

@@ -42,3 +42,15 @@ func slicesdelete(test, other []byte, i int) {
 
 	_ = append(test[:1+2], test[i-1:]...) // cannot verify a < b
 }
+
+func issue73663(test, other []byte, i int32) {
+	const k = 1
+	_ = append(test[:i], test[i+1:]...) // want "Replace append with slices.Delete"
+
+	_ = append(test[:i-1], test[i:]...) // want "Replace append with slices.Delete"
+
+	_ = append(g.f[:i], g.f[i+k:]...) // want "Replace append with slices.Delete"
+
+	type int string // int is shadowed, so no offered fix.
+	_ = append(test[:i], test[i+1:]...)
+}

gopls/internal/analysis/modernize/testdata/src/slicesdelete/slicesdelete.go.golden

@@ -44,3 +44,15 @@ func slicesdelete(test, other []byte, i int) {
 
 	_ = append(test[:1+2], test[i-1:]...) // cannot verify a < b
 }
+
+func issue73663(test, other []byte, i int32) {
+	const k = 1
+	_ = slices.Delete(test, int(i), int(i+1)) // want "Replace append with slices.Delete"
+
+	_ = slices.Delete(test, int(i-1), int(i)) // want "Replace append with slices.Delete"
+
+	_ = slices.Delete(g.f, int(i), int(i+k)) // want "Replace append with slices.Delete"
+
+	type int string // int is shadowed, so no offered fix.
+	_ = append(test[:i], test[i+1:]...)
+}