checker: disallow assigning number to pointer (#7267)

vlib/builtin/builtin_nix.c.v

@@ -140,6 +140,6 @@ fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
 fn break_if_debugger_attached() {
 	unsafe {
 		mut ptr := &voidptr(0)
-		*ptr = 0
+		*ptr = voidptr(0)
 	}
 }

vlib/builtin/builtin_windows.c.v

@@ -234,7 +234,7 @@ fn break_if_debugger_attached() {
 	$if tinyc {
 		unsafe {
 			mut ptr := &voidptr(0)
-			*ptr = 0
+			*ptr = voidptr(0)
 		}
 	} $else {
 		if C.IsDebuggerPresent() {

vlib/clipboard/clipboard_linux.c.v

@@ -425,9 +425,7 @@ fn (cb &Clipboard) get_supported_targets() []C.Atom {
 }
 
 fn new_atom(value int) &C.Atom {
-	mut atom := &C.Atom{}
+	return unsafe {&C.Atom(value)}
-	atom = value
-	return atom
 }
 
 fn create_xwindow(display &C.Display) C.Window {

vlib/live/executable/reloader.v

@@ -118,7 +118,7 @@ fn load_lib(mut r live.LiveReloadInfo, new_lib_path string) {
 fn protected_load_lib(mut r live.LiveReloadInfo, new_lib_path string) {
 	if r.live_lib != 0 {
 		dl.close( r.live_lib )
-		r.live_lib = 0
+		r.live_lib = C.NULL
 	}
 	r.live_lib = dl.open(new_lib_path, dl.rtld_lazy)
 	if r.live_lib == 0 {

vlib/v/checker/check_types.v

@@ -283,9 +283,14 @@ pub fn (mut c Checker) check_expected(got table.Type, expected table.Type) ? {
 	if c.check_types(got, expected) {
 		return
 	}
+	return error(c.expected_msg(got, expected))
+}
+
+[inline]
+fn (c &Checker) expected_msg(got table.Type, expected table.Type) string {
 	exps := c.table.type_to_str(expected)
 	gots := c.table.type_to_str(got)
-	return error('expected `$exps`, not `$gots`')
+	return 'expected `$exps`, not `$gots`'
 }
 
 pub fn (mut c Checker) symmetric_check(left table.Type, right table.Type) bool {

vlib/v/checker/checker.v

@@ -2173,18 +2173,23 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 		}
 		left_sym := c.table.get_type_symbol(left_type_unwrapped)
 		right_sym := c.table.get_type_symbol(right_type_unwrapped)
-		left_is_ptr := left_type.is_ptr() || left_sym.is_pointer()
-		right_is_ptr := right_type.is_ptr() || right_sym.is_pointer()
-		if left_is_ptr && assign_stmt.op !in [.assign, .decl_assign] && !c.inside_unsafe {
-			// ptr op=
-			c.warn('pointer arithmetic is only allowed in `unsafe` blocks', assign_stmt.pos)
-		}
 		if c.pref.translated {
 			// TODO fix this in C2V instead, for example cast enums to int before using `|` on them.
 			// TODO replace all c.pref.translated checks with `$if !translated` for performance
 			continue
 		}
-		if left_is_ptr && (right is ast.StructInit || !right_is_ptr) && !right_sym.is_number() {
+		left_is_ptr := left_type.is_ptr() || left_sym.is_pointer()
+		if left_is_ptr {
+			if !c.inside_unsafe && assign_stmt.op !in [.assign, .decl_assign] {
+				// ptr op=
+				c.warn('pointer arithmetic is only allowed in `unsafe` blocks', assign_stmt.pos)
+			}
+			right_is_ptr := right_type.is_ptr() || right_sym.is_pointer()
+			if !right_is_ptr && assign_stmt.op == .assign && right_type_unwrapped.is_number() {
+				c.error('cannot assign to `$left`: ' +
+					c.expected_msg(right_type_unwrapped, left_type_unwrapped), right.position())
+			}
+			if (right is ast.StructInit || !right_is_ptr) && !right_sym.is_number() {
 				left_name := c.table.type_to_str(left_type_unwrapped)
 				mut rtype := right_type_unwrapped
 				if rtype.is_ptr() {
@@ -2193,6 +2198,7 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 				right_name := c.table.type_to_str(rtype)
 				c.error('mismatched types `$left_name` and `$right_name`', assign_stmt.pos)
 			}
+		}
 		// Single side check
 		match assign_stmt.op {
 			.assign {} // No need to do single side check for =. But here put it first for speed.
@@ -3364,6 +3370,9 @@ pub fn (mut c Checker) ident(mut ident ast.Ident) table.Type {
 		}
 	}
 	if ident.language == .c {
+		if ident.name == 'C.NULL' {
+			return table.voidptr_type
+		}
 		return table.int_type
 	}
 	if c.inside_sql {

vlib/v/checker/tests/ptr_assign.out

@@ -0,0 +1,5 @@
+vlib/v/checker/tests/ptr_assign.vv:3:5: error: cannot assign to `p`: expected `&int`, not `any_int`
+    1 | mut v := 43
+    2 | mut p := &v
+    3 | p = 4
+      |     ^

vlib/v/checker/tests/ptr_assign.vv

@@ -0,0 +1,3 @@
+mut v := 43
+mut p := &v
+p = 4

vlib/v/gen/js/js.v

@@ -193,7 +193,7 @@ pub fn (mut g JsGen) enter_namespace(name string) {
 }
 
 pub fn (mut g JsGen) escape_namespace() {
-	g.ns = 0
+	g.ns = &Namespace(0)
 	g.inside_builtin = false
 }
 

vlib/v/tests/interop_test.v

@@ -14,3 +14,8 @@ fn JS.f(a &Foo) // TODO: Should this be allowed?
 fn C.g(string, ...int)
 fn C.h(&int)
 fn JS.i(...string)
+
+fn test_null() {
+	np := C.NULL
+	assert typeof(np).name == 'voidptr'
+}