checker: stricter mutable reference check (fix #14803) (#14805)

vlib/dlmalloc/dlmalloc.v

@@ -357,7 +357,7 @@ fn (mut c Chunk) set_size_and_pinuse_of_free_chunk(size usize) {
 }
 
 fn (mut c Chunk) set_free_with_pinuse(size usize, n_ &Chunk) {
-	mut n := n_
+	mut n := unsafe { n_ }
 	n.clear_pinuse()
 	c.set_size_and_pinuse_of_free_chunk(size)
 }
@@ -480,7 +480,7 @@ fn (mut dl Dlmalloc) unlink_chunk(chunk &Chunk, size usize) {
 
 [unsafe]
 fn (mut dl Dlmalloc) unlink_small_chunk(chunk_ &Chunk, size usize) {
-	mut chunk := chunk_
+	mut chunk := unsafe { chunk_ }
 	mut f := chunk.prev
 	mut b := chunk.next
 	idx := small_index(size)
@@ -563,8 +563,8 @@ fn (mut dl Dlmalloc) unlink_large_chunk(chunk_ &TreeChunk) {
 
 [unsafe]
 fn (mut dl Dlmalloc) unlink_first_small_chunk(head_ &Chunk, next_ &Chunk, idx u32) {
-	mut next := next_
-	mut head := head_
+	mut next := unsafe { next_ }
+	mut head := unsafe { head_ }
 	println('Unlink first small')
 	mut ptr := next.prev
 	if voidptr(head) == voidptr(ptr) {
@@ -815,7 +815,7 @@ fn (mut dl Dlmalloc) insert_chunk(chunk &Chunk, size usize) {
 
 [unsafe]
 fn (mut dl Dlmalloc) insert_small_chunk(chunk_ &Chunk, size usize) {
-	mut chunk := chunk_
+	mut chunk := unsafe { chunk_ }
 	idx := small_index(size)
 	unsafe {
 		mut head := dl.smallbin_at(idx)
@@ -837,8 +837,8 @@ fn (mut dl Dlmalloc) insert_small_chunk(chunk_ &Chunk, size usize) {
 
 [unsafe]
 fn (mut dl Dlmalloc) insert_large_chunk(chunk_ &TreeChunk, size usize) {
-	mut chunk := chunk_
 	unsafe {
+		mut chunk := chunk_
 		idx := dl.compute_tree_index(size)
 		mut h := dl.treebin_at(idx)
 
@@ -1527,7 +1527,7 @@ fn (mut dl Dlmalloc) try_realloc_chunk(p_ &Chunk, nb usize, can_move bool) &Chun
 
 [unsafe]
 fn (mut dl Dlmalloc) mmap_resize(oldp_ &Chunk, nb usize, can_move bool) &Chunk {
-	mut oldp := oldp_
+	mut oldp := unsafe { oldp_ }
 	oldsize := oldp.size()
 	if is_small(nb) {
 		return voidptr(0)
@@ -1568,7 +1568,7 @@ fn (dl &Dlmalloc) mmap_align(a usize) usize {
 
 [unsafe]
 fn (mut dl Dlmalloc) dispose_chunk(p_ &Chunk, psize_ usize) {
-	mut p := p_
+	mut p := unsafe { p_ }
 	mut psize := psize_
 	unsafe {
 		mut next := p.plus_offset(psize)

vlib/net/address.v

@@ -205,7 +205,7 @@ pub fn resolve_ipaddrs(addr string, family AddrFamily, typ SocketType) ?[]Addr {
 	// convert them into an array
 	mut addresses := []Addr{}
 
-	for result := results; !isnil(result); result = result.ai_next {
+	for result := unsafe { results }; !isnil(result); result = result.ai_next {
 		match AddrFamily(result.ai_family) {
 			.ip {
 				new_addr := Addr{

vlib/term/ui/input_windows.c.v

@@ -86,7 +86,7 @@ pub fn init(cfg Config) &Context {
 	C.atexit(restore_terminal_state)
 	for code in ctx.cfg.reset {
 		os.signal_opt(code, fn (_ os.Signal) {
-			mut c := ui.ctx_ptr
+			mut c := unsafe { ui.ctx_ptr }
 			if unsafe { c != 0 } {
 				c.cleanup()
 			}

vlib/term/ui/termios_nix.c.v

@@ -43,7 +43,7 @@ fn restore_terminal_state_signal(_ os.Signal) {
 
 fn restore_terminal_state() {
 	termios_reset()
-	mut c := ctx_ptr
+	mut c := unsafe { ctx_ptr }
 	if unsafe { c != 0 } {
 		c.paused = true
 		load_title()
@@ -125,7 +125,7 @@ fn (mut ctx Context) termios_setup() ? {
 	C.atexit(restore_terminal_state)
 	os.signal_opt(.tstp, restore_terminal_state_signal) or {}
 	os.signal_opt(.cont, fn (_ os.Signal) {
-		mut c := ctx_ptr
+		mut c := unsafe { ctx_ptr }
 		if unsafe { c != 0 } {
 			c.termios_setup() or { panic(err) }
 			c.window_height, c.window_width = get_terminal_size()
@@ -140,7 +140,7 @@ fn (mut ctx Context) termios_setup() ? {
 	}) or {}
 	for code in ctx.cfg.reset {
 		os.signal_opt(code, fn (_ os.Signal) {
-			mut c := ctx_ptr
+			mut c := unsafe { ctx_ptr }
 			if unsafe { c != 0 } {
 				c.cleanup()
 			}
@@ -149,7 +149,7 @@ fn (mut ctx Context) termios_setup() ? {
 	}
 
 	os.signal_opt(.winch, fn (_ os.Signal) {
-		mut c := ctx_ptr
+		mut c := unsafe { ctx_ptr }
 		if unsafe { c != 0 } {
 			c.window_height, c.window_width = get_terminal_size()
 

vlib/v/ast/scope.v

@@ -42,7 +42,7 @@ fn (s &Scope) dont_lookup_parent() bool {
 }
 
 pub fn (s &Scope) find(name string) ?ScopeObject {
-	for sc := s; true; sc = sc.parent {
+	for sc := unsafe { s }; true; sc = sc.parent {
 		if name in sc.objects {
 			return unsafe { sc.objects[name] }
 		}
@@ -55,7 +55,7 @@ pub fn (s &Scope) find(name string) ?ScopeObject {
 
 // selector_expr:  name.field_name
 pub fn (s &Scope) find_struct_field(name string, struct_type Type, field_name string) ?ScopeStructField {
-	for sc := s; true; sc = sc.parent {
+	for sc := unsafe { s }; true; sc = sc.parent {
 		if field := sc.struct_fields[name] {
 			if field.struct_type == struct_type && field.name == field_name {
 				return field

vlib/v/checker/assign.v

@@ -157,6 +157,13 @@ pub fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 					}
 				}
 			}
+			if mut left is ast.Ident && mut right is ast.Ident {
+				if !c.inside_unsafe && left_type.is_ptr() && left.is_mut() && right_type.is_ptr()
+					&& !right.is_mut() {
+					c.error('`$right.name` is immutable, cannot have a mutable reference to an immutable object',
+						right.pos)
+				}
+			}
 		} else {
 			// Make sure the variable is mutable
 			c.fail_if_immutable(left)

vlib/v/checker/checker.v

@@ -174,7 +174,7 @@ fn (mut c Checker) reset_checker_state_at_start_of_new_file() {
 }
 
 pub fn (mut c Checker) check(ast_file_ &ast.File) {
-	mut ast_file := ast_file_
+	mut ast_file := unsafe { ast_file_ }
 	c.reset_checker_state_at_start_of_new_file()
 	c.change_current_file(ast_file)
 	for i, ast_import in ast_file.imports {

vlib/v/checker/fn.v

@@ -877,7 +877,7 @@ pub fn (mut c Checker) fn_call(mut node ast.CallExpr, mut continue_check &bool)
 				c.fail_if_unreadable(call_arg.expr, arg_typ, 'argument')
 			}
 		}
-		mut final_param_sym := param_typ_sym
+		mut final_param_sym := unsafe { param_typ_sym }
 		mut final_param_typ := param.typ
 		if func.is_variadic && param_typ_sym.info is ast.Array {
 			final_param_typ = param_typ_sym.info.elem_type
@@ -1349,7 +1349,7 @@ pub fn (mut c Checker) method_call(mut node ast.CallExpr) ast.Type {
 				c.error('when forwarding a variadic variable, it must be the final argument',
 					arg.pos)
 			}
-			mut final_arg_sym := exp_arg_sym
+			mut final_arg_sym := unsafe { exp_arg_sym }
 			mut final_arg_typ := exp_arg_typ
 			if method.is_variadic && exp_arg_sym.info is ast.Array {
 				final_arg_typ = exp_arg_sym.info.elem_type

vlib/v/checker/tests/assign_immutable_reference_var_err.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/assign_immutable_reference_var_err.vv:8:11: error: `x` is immutable, cannot have a mutable reference to an immutable object
+    6 |
+    7 | fn y(x &Foo) {
+    8 |     mut m := x
+      |              ^
+    9 |     m.value = 42
+   10 | }

vlib/v/checker/tests/assign_immutable_reference_var_err.vv

@@ -0,0 +1,16 @@
+[heap]
+struct Foo {
+mut:
+	value int
+}
+
+fn y(x &Foo) {
+	mut m := x
+	m.value = 42
+}
+
+fn main() {
+	x := Foo{123}
+	y(x)
+	println(x)
+}

vlib/v/parser/containers.v

@@ -89,7 +89,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 					p.scope_register_it_as_index()
 					default_expr = p.expr(0)
 					has_it = if var := p.scope.find_var('it') {
-						mut variable := var
+						mut variable := unsafe { var }
 						is_used := variable.is_used
 						variable.is_used = true
 						is_used
@@ -148,7 +148,7 @@ fn (mut p Parser) array_init() ast.ArrayInit {
 					p.scope_register_it_as_index()
 					default_expr = p.expr(0)
 					has_it = if var := p.scope.find_var('it') {
-						mut variable := var
+						mut variable := unsafe { var }
 						is_used := variable.is_used
 						variable.is_used = true
 						is_used