go/types, types2: refuse pointer to array as argument to "clear" builtin

The accepted proposal only permits map and slice types.

Updates #56351

Change-Id: I95cf4c856a5ecfcdf564601b6215eda3cb6ba86b
Reviewed-on: https://go-review.googlesource.com/c/go/+/463075
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>

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

@@ -240,15 +240,11 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 		}
 
 		if !underIs(x.typ, func(u Type) bool {
-			switch u := u.(type) {
+			switch u.(type) {
 			case *Map, *Slice:
 				return true
-			case *Pointer:
-				if _, ok := under(u.base).(*Array); ok {
-					return true
 			}
-			}
+			check.errorf(x, InvalidClear, invalidArg+"cannot clear %s: argument must be (or constrained by) map or slice", x)
-			check.errorf(x, InvalidClear, invalidArg+"cannot clear %s: argument must be (or constrained by) map, slice, or array pointer", x)
 			return false
 		}) {
 			return

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

@@ -42,8 +42,6 @@ var builtinCalls = []struct {
 
 	{"clear", `var m map[float64]int; clear(m)`, `func(map[float64]int)`},
 	{"clear", `var s []byte; clear(s)`, `func([]byte)`},
-	{"clear", `var p *[10]int; clear(p)`, `func(*[10]int)`},
-	{"clear", `var s P; clear(s)`, `func(P)`},
 
 	{"close", `var c chan int; close(c)`, `func(chan int)`},
 	{"close", `var c chan<- chan string; close(c)`, `func(chan<- chan string)`},

src/go/types/builtins.go

@@ -241,15 +241,11 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		}
 
 		if !underIs(x.typ, func(u Type) bool {
-			switch u := u.(type) {
+			switch u.(type) {
 			case *Map, *Slice:
 				return true
-			case *Pointer:
-				if _, ok := under(u.base).(*Array); ok {
-					return true
 			}
-			}
+			check.errorf(x, InvalidClear, invalidArg+"cannot clear %s: argument must be (or constrained by) map or slice", x)
-			check.errorf(x, InvalidClear, invalidArg+"cannot clear %s: argument must be (or constrained by) map, slice, or array pointer", x)
 			return false
 		}) {
 			return

src/go/types/builtins_test.go

@@ -42,8 +42,6 @@ var builtinCalls = []struct {
 
 	{"clear", `var m map[float64]int; clear(m)`, `func(map[float64]int)`},
 	{"clear", `var s []byte; clear(s)`, `func([]byte)`},
-	{"clear", `var p *[10]int; clear(p)`, `func(*[10]int)`},
-	{"clear", `var s P; clear(s)`, `func(P)`},
 
 	{"close", `var c chan int; close(c)`, `func(chan int)`},
 	{"close", `var c chan<- chan string; close(c)`, `func(chan<- chan string)`},

src/internal/types/errors/codes.go

@@ -1432,7 +1432,7 @@ const (
 	_ // not used anymore
 
 	// InvalidClear occurs when clear is called with an argument
-	// that is not of map, slice, or pointer-to-array type.
+	// that is not of map or slice type.
 	//
 	// Example:
 	//  func _(x int) {

src/internal/types/testdata/check/builtins0.go

@@ -144,7 +144,7 @@ func clear1() {
 	var m map[float64]string
 	var s []byte
 	clear(a /* ERROR "cannot clear a" */)
-	clear(&a)
+	clear(&/* ERROR "cannot clear &a" */a)
 	clear(m)
 	clear(s)
 	clear([]int{})

src/internal/types/testdata/check/builtins1.go

@@ -14,7 +14,7 @@ func _[T any](x T) {
 	clear(x /* ERROR "cannot clear x" */)
 }
 
-func _[T ~map[int]string | ~[]byte | ~*[10]int](x T) {
+func _[T ~map[int]string | ~[]byte](x T) {
 	clear(x)
 }