go/types, types2: report error for invalid string(1 << s)

For #45114.
Fixes #45117.

Change-Id: I71d6650ae2c4c06952fce19959120f15f13c08a2
Reviewed-on: https://go-review.googlesource.com/c/go/+/379256
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

src/cmd/compile/internal/types2/api_test.go

@@ -109,7 +109,6 @@ func TestValuesInfo(t *testing.T) {
 		{`package c5d; var _ = string(65)`, `65`, `untyped int`, `65`},
 		{`package c5e; var _ = string('A')`, `'A'`, `untyped rune`, `65`},
 		{`package c5f; type T string; var _ = T('A')`, `'A'`, `untyped rune`, `65`},
-		{`package c5g; var s uint; var _ = string(1 << s)`, `1 << s`, `untyped int`, ``},
 
 		{`package d0; var _ = []byte("foo")`, `"foo"`, `string`, `"foo"`},
 		{`package d1; var _ = []byte(string("foo"))`, `"foo"`, `string`, `"foo"`},

src/cmd/compile/internal/types2/conversions.go

@@ -98,13 +98,13 @@ func (check *Checker) conversion(x *operand, T Type) {
 		// - For conversions of untyped constants to non-constant types, also
 		//   use the default type (e.g., []byte("foo") should report string
 		//   not []byte as type for the constant "foo").
-		// - For integer to string conversions, keep the argument type.
+		// - For constant integer to string conversions, keep the argument type.
 		//   (See also the TODO below.)
 		if x.typ == Typ[UntypedNil] {
 			// ok
 		} else if IsInterface(T) && !isTypeParam(T) || constArg && !isConstType(T) {
 			final = Default(x.typ)
-		} else if isInteger(x.typ) && allString(T) {
+		} else if x.mode == constant_ && isInteger(x.typ) && allString(T) {
 			final = x.typ
 		}
 		check.updateExprType(x.expr, final, true)

src/cmd/compile/internal/types2/testdata/check/shifts.src

@@ -381,7 +381,7 @@ func issue21727() {
 	var a = make([]int, 1<<s + 1.2 /* ERROR "truncated to int" */ )
 	var _ = a[1<<s - 2.3 /* ERROR "truncated to int" */ ]
 	var _ int = 1<<s + 3.4 /* ERROR "truncated to int" */
-	var _ = string(1 << s)
+	var _ = string(1 /* ERROR shifted operand 1 .* must be integer */ << s)
 	var _ = string(1.0 /* ERROR "cannot convert" */ << s)
 }
 

src/cmd/compile/internal/types2/testdata/fixedbugs/issue45114.go

@@ -0,0 +1,8 @@
+// Copyright 2022 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.
+
+package p
+
+var s uint
+var _ = string(1 /* ERROR shifted operand 1 .* must be integer */ << s)

src/go/types/api_test.go

@@ -127,7 +127,6 @@ func TestValuesInfo(t *testing.T) {
 		{`package c5d; var _ = string(65)`, `65`, `untyped int`, `65`},
 		{`package c5e; var _ = string('A')`, `'A'`, `untyped rune`, `65`},
 		{`package c5f; type T string; var _ = T('A')`, `'A'`, `untyped rune`, `65`},
-		{`package c5g; var s uint; var _ = string(1 << s)`, `1 << s`, `untyped int`, ``},
 
 		{`package d0; var _ = []byte("foo")`, `"foo"`, `string`, `"foo"`},
 		{`package d1; var _ = []byte(string("foo"))`, `"foo"`, `string`, `"foo"`},

src/go/types/conversions.go

@@ -96,11 +96,11 @@ func (check *Checker) conversion(x *operand, T Type) {
 		//   use the default type (e.g., []byte("foo") should report string
 		//   not []byte as type for the constant "foo").
 		// - Keep untyped nil for untyped nil arguments.
-		// - For integer to string conversions, keep the argument type.
+		// - For constant integer to string conversions, keep the argument type.
 		//   (See also the TODO below.)
 		if IsInterface(T) && !isTypeParam(T) || constArg && !isConstType(T) || x.isNil() {
 			final = Default(x.typ) // default type of untyped nil is untyped nil
-		} else if isInteger(x.typ) && allString(T) {
+		} else if x.mode == constant_ && isInteger(x.typ) && allString(T) {
 			final = x.typ
 		}
 		check.updateExprType(x.expr, final, true)

src/go/types/testdata/check/shifts.src

@@ -380,7 +380,7 @@ func issue21727() {
 	var a = make([]int, 1<<s + 1.2 /* ERROR "truncated to int" */ )
 	var _ = a[1<<s - 2.3 /* ERROR "truncated to int" */ ]
 	var _ int = 1<<s + 3.4 /* ERROR "truncated to int" */
-	var _ = string(1 << s)
+	var _ = string(1 /* ERROR shifted operand 1 .* must be integer */ << s)
 	var _ = string(1.0 /* ERROR "cannot convert" */ << s)
 }
 

src/go/types/testdata/fixedbugs/issue45114.go

@@ -0,0 +1,8 @@
+// Copyright 2022 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.
+
+package p
+
+var s uint
+var _ = string(1 /* ERROR shifted operand 1 .* must be integer */ << s)

test/fixedbugs/bug193.go

@@ -11,8 +11,6 @@ func main() {
 	ss := 1 << s
 	y1 := float64(ss)
 	y2 := float64(1 << s) // ERROR "shift"
-	// see issues #45114, #45117
-	// y3 := string(1 << s)  // DISABLED "shift"
-	y3 := 0
+	y3 := string(1 << s)  // ERROR "shift"
 	_, _, _, _, _ = s, ss, y1, y2, y3
 }