gopls/internal/analysis/modernize: use types.RelativeTo to respect current package

This CL fixes a bug introduced in CL659155. It leverages types.RelativeTo
to determine the package name of a variable, ensuring that the package
name is not added for types declared within the same package. This prevents
invalid type errors.

Additionally, this CL introduces additional test cases.

Fixes golang/go#73037

Change-Id: I6ad0c80c02ad1a679a956b93a53a05a8eb1ba9c2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/660815
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: xieyuschen

gopls/internal/analysis/modernize/rangeint.go

@@ -184,7 +184,7 @@ func rangeint(pass *analysis.Pass) {
 							// (Unfortunately types.Qualifier doesn't provide the name of the package
 							// member to be qualified, a qualifier cannot perform the necessary shadowing
 							// check for dot-imported names.)
-							beforeLimit, afterLimit = fmt.Sprintf("%s(", types.TypeString(tVar, (*types.Package).Name)), ")"
+							beforeLimit, afterLimit = fmt.Sprintf("%s(", types.TypeString(tVar, types.RelativeTo(pass.Pkg))), ")"
 							info2 := &types.Info{Types: make(map[ast.Expr]types.TypeAndValue)}
 							if types.CheckExpr(pass.Fset, pass.Pkg, limit.Pos(), limit, info2) == nil {
 								tLimit := types.Default(info2.TypeOf(limit))

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

@@ -205,3 +205,29 @@ func todo() {
 		println(j)
 	}
 }
+
+type T uint
+type TAlias = uint
+
+func Fn(a int) T {
+	return T(a)
+}
+
+func issue73037() {
+	var q T
+	for a := T(0); a < q; a++ { // want "for loop can be modernized using range over int"
+		println(a)
+	}
+	for a := Fn(0); a < q; a++ {
+		println(a)
+	}
+	var qa TAlias
+	for a := TAlias(0); a < qa; a++ { // want "for loop can be modernized using range over int"
+		println(a)
+	}
+	for a := T(0); a < 10; a++ { // want "for loop can be modernized using range over int"
+		for b := T(0); b < 10; b++ { // want "for loop can be modernized using range over int"
+			println(a, b)
+		}
+	}
+}

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

@@ -205,3 +205,29 @@ func todo() {
 		println(j)
 	}
 }
+
+type T uint
+type TAlias = uint
+
+func Fn(a int) T {
+	return T(a)
+}
+
+func issue73037() {
+    var q T
+	for a := range q { // want "for loop can be modernized using range over int"
+	    println(a)
+	}
+	for a := Fn(0); a < q; a++ {
+		println(a)
+	}
+    var qa TAlias
+    for a := range qa { // want "for loop can be modernized using range over int"
+        println(a)
+    }
+	for a := range T(10) { // want "for loop can be modernized using range over int"
+		for b := range T(10) { // want "for loop can be modernized using range over int"
+			println(a, b)
+		}
+	}
+}