checker: add a check for `ptr = Abc{}`

vlib/os/os_c.v

@@ -2,27 +2,41 @@ module os
 
 #include <sys/stat.h> // #include <signal.h>
 #include <errno.h>
+struct C.dirent {
+	d_name [256]char
+}
+
+fn C.readdir(voidptr) &C.dirent
 
-fn C.readdir(voidptr) C.dirent
 fn C.getpid() int
-fn C.readlink() int
-fn C.getline(voidptr, voidptr, voidptr) int
-fn C.ftell(fp voidptr) int
-fn C.sigaction(int, voidptr, int)
-fn C.open(charptr, int, int) int
-fn C.fdopen(int, string) voidptr
-fn C.CopyFile(&u32, &u32, int) int
-fn C.fork() int
-fn C.wait() int
-//fn C.proc_pidpath(int, byteptr, int) int
 
+fn C.readlink() int
+
+fn C.getline(voidptr, voidptr, voidptr) int
+
+fn C.ftell(fp voidptr) int
+
+fn C.sigaction(int, voidptr, int)
+
+fn C.open(charptr, int, int) int
+
+fn C.fdopen(int, string) voidptr
+
+fn C.CopyFile(&u32, &u32, int) int
+
+fn C.fork() int
+
+fn C.wait() int
+
+// fn C.proc_pidpath(int, byteptr, int) int
 struct C.stat {
 	st_size  int
 	st_mode  u32
 	st_mtime int
 }
 
-struct C.DIR {}
+struct C.DIR {
+}
 
 struct C.sigaction {
 mut:

vlib/v/checker/checker.v

@@ -2080,8 +2080,9 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 		right_type_unwrapped := c.unwrap_generic(right_type)
 		left_sym := c.table.get_type_symbol(left_type_unwrapped)
 		right_sym := c.table.get_type_symbol(right_type_unwrapped)
-		if (left_type.is_ptr() || left_sym.is_pointer()) &&
+		left_is_ptr := left_type.is_ptr() || left_sym.is_pointer()
-			assign_stmt.op !in [.assign, .decl_assign] && !c.inside_unsafe {
+		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)
 		}
@@ -2090,6 +2091,15 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 			// TODO replace all c.pref.translated checks with `$if !translated` for performance
 			continue
 		}
+		if left_is_ptr && (right is ast.StructInit || !right_is_ptr) && !right_sym.is_number() {
+			left_name := c.table.type_to_str(left_type_unwrapped)
+			mut rtype := right_type_unwrapped
+			if rtype.is_ptr() {
+				rtype = rtype.deref()
+			}
+			right_name := c.table.type_to_str(rtype)
+			c.error('mismatched types `$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.

vlib/v/checker/tests/struct_assigned_to_pointer_to_struct.out

@@ -0,0 +1,13 @@
+vlib/v/checker/tests/struct_assigned_to_pointer_to_struct.vv:5:4: error: mismatched types `&Foo` and `Foo`
+    3 | fn main() {
+    4 |     mut f := &Foo{ 10 }
+    5 |     f = { x: 223344 }
+      |       ^
+    6 |     f = Foo{ x: 20 }
+    7 | }
+vlib/v/checker/tests/struct_assigned_to_pointer_to_struct.vv:6:4: error: mismatched types `&Foo` and `Foo`
+    4 |     mut f := &Foo{ 10 }
+    5 |     f = { x: 223344 }
+    6 |     f = Foo{ x: 20 }
+      |       ^
+    7 | }

vlib/v/checker/tests/struct_assigned_to_pointer_to_struct.vv

@@ -0,0 +1,7 @@
+struct Foo { x int }
+
+fn main() {
+	mut f := &Foo{ 10 }
+	f = { x: 223344 }
+	f = Foo{ x: 20 }
+}