all: @[freed] attribute for assign statements

vlib/v/ast/ast.v

@@ -1312,6 +1312,7 @@ pub mut:
 	is_volatile   bool // for disabling variable access optimisations (needed for hardware drivers)
 	is_simple     bool // `x+=2` in `for x:=1; ; x+=2`
 	has_cross_var bool
+	attr          Attr
 }
 
 // `expr as Ident`

vlib/v/checker/assign.v

@@ -8,6 +8,11 @@ import v.ast
 fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 	prev_inside_assign := c.inside_assign
 	c.inside_assign = true
+	if node.attr.name != '' {
+		c.assign_stmt_attr = node.attr.name
+	} else {
+		c.assign_stmt_attr = ''
+	}
 	c.expected_type = ast.none_type // TODO: a hack to make `x := if ... work`
 	defer {
 		c.expected_type = ast.void_type

vlib/v/checker/checker.v

@@ -135,6 +135,7 @@ mut:
 	orm_table_fields  map[string][]ast.StructField // known table structs
 	//
 	v_current_commit_hash string // same as old C.V_CURRENT_COMMIT_HASH
+	assign_stmt_attr      string // for `x := [1,2,3] @[freed]`
 }
 
 pub fn new_checker(table &ast.Table, pref_ &pref.Preferences) &Checker {

vlib/v/checker/errors.v

@@ -33,6 +33,10 @@ fn (mut c Checker) warn(s string, pos token.Pos) {
 }
 
 fn (mut c Checker) warn_alloc(s string, pos token.Pos) {
+	if c.assign_stmt_attr == 'freed' {
+		return
+	}
+
 	if !c.is_builtin_mod && c.mod !in ['strings', 'math', 'math.bits', 'builtin', 'strconv'] {
 		c.warn('allocation (${s})', pos)
 	}

vlib/v/fmt/fmt.v

@@ -879,6 +879,9 @@ pub fn (mut f Fmt) assign_stmt(node ast.AssignStmt) {
 			f.write(', ')
 		}
 	}
+	if node.attr.name != '' {
+		f.write(' @[${node.attr.name}]')
+	}
 	f.comments(node.end_comments, has_nl: false, same_line: true, level: .keep)
 	if !f.single_line_if {
 		f.writeln('')

vlib/v/fmt/tests/stmt_attr_keep.vv

@@ -0,0 +1,7 @@
+fn foo() {
+	x := [1, 2, 3] @[freed]
+	unsafe {
+		x.free()
+	}
+	println('x is freed')
+}

vlib/v/parser/assign.v

@@ -285,6 +285,14 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr) ast.Stmt {
 			}
 		}
 	}
+	mut attr := ast.Attr{}
+	// This assign stmt has an attribute e.g. `x := [1,2,3] @[freed]`
+	if p.tok.kind == .at && p.tok.line_nr == p.prev_tok.line_nr {
+		p.check(.at)
+		p.check(.lsbr)
+		attr = p.parse_attr(true)
+		p.check(.rsbr)
+	}
 	pos.update_last_line(p.prev_tok.line_nr)
 	p.expr_mod = ''
 	return ast.AssignStmt{
@@ -297,5 +305,6 @@ fn (mut p Parser) partial_assign_stmt(left []ast.Expr) ast.Stmt {
 		is_simple: p.inside_for && p.tok.kind == .lcbr
 		is_static: is_static
 		is_volatile: is_volatile
+		attr: attr
 	}
 }