checker: check ! operator

vlib/v/ast/ast.v

@@ -319,18 +319,6 @@ mut:
 	right_type table.Type
 }
 
-/*
-// renamed to PrefixExpr
-pub struct UnaryExpr {
-pub:
-// tok_kind token.Kind
-// op    BinaryOp
-	op   token.Kind
-	left Expr
-}
-*/
-
-
 pub struct PostfixExpr {
 pub:
 	op   token.Kind
@@ -342,6 +330,7 @@ pub struct PrefixExpr {
 pub:
 	op    token.Kind
 	right Expr
+	pos   token.Position
 }
 
 pub struct IndexExpr {

vlib/v/checker/checker.v

@@ -746,6 +746,9 @@ pub fn (c mut Checker) expr(node ast.Expr) table.Type {
 			if it.op == .mul && table.type_is_ptr(right_type) {
 				return table.type_deref(right_type)
 			}
+			if it.op == .not && right_type != table.bool_type_idx {
+				c.error('! operator can only be used with bool types', it.pos)
+			}
 			return right_type
 		}
 		ast.None {

vlib/v/parser/parser.v

@@ -71,6 +71,7 @@ pub fn parse_file(path string, table &table.Table, comments_mode scanner.Comment
 		table: table
 		file_name: path
 		pref: pref // &pref.Preferences{}
+		
 		scope: &ast.Scope{
 			start_pos: 0
 			parent: 0
@@ -904,6 +905,7 @@ pub fn (p mut Parser) expr(precedence int) ast.Expr {
 }
 
 fn (p mut Parser) prefix_expr() ast.PrefixExpr {
+	pos := p.tok.position()
 	op := p.tok.kind
 	if op == .amp {
 		p.is_amp = true
@@ -914,6 +916,7 @@ fn (p mut Parser) prefix_expr() ast.PrefixExpr {
 	return ast.PrefixExpr{
 		op: op
 		right: right
+		pos: pos
 	}
 }