gen/checker: add errors for as cast & for in var

vlib/v/ast/ast.v

@@ -377,8 +377,8 @@ pub struct ForStmt {
 pub:
 	cond   Expr
 	stmts  []Stmt
-	pos    token.Position
 	is_inf bool // `for {}`
+	pos    token.Position
 }
 
 pub struct ForInStmt {
@@ -400,12 +400,13 @@ pub:
 	// inc   Stmt // i++;
 	inc      Expr // i++;
 	stmts    []Stmt
+	pos      token.Position
 }
 
 pub struct ReturnStmt {
 	tok_kind token.Kind // or pos
-	pos      token.Position
 	results  []Expr
+	pos      token.Position
 }
 
 // #include etc
@@ -435,6 +436,7 @@ pub struct AsCast {
 pub:
 	expr      Expr
 	typ       table.Type
+	pos       token.Position
 mut:
 	expr_type table.Type
 }

vlib/v/checker/checker.v

@@ -618,6 +618,18 @@ pub fn (c mut Checker) expr(node ast.Expr) table.Type {
 		}
 		ast.AsCast {
 			it.expr_type = c.expr(it.expr)
+			expr_type_sym := c.table.get_type_symbol(it.expr_type)
+			type_sym := c.table.get_type_symbol(it.typ)
+			if expr_type_sym.kind == .sum_type {
+				info := expr_type_sym.info as table.SumType
+				if !it.typ in info.variants {
+					c.error('cannot cast `$expr_type_sym.name` to `$type_sym.name`', it.pos)
+					// c.error('only $info.variants can be casted to `$typ`', it.pos)
+				}
+			}
+			else {
+				c.error('cannot cast non sum type `$type_sym.name` using `as`', it.pos)
+			}
 			return it.typ
 		}
 		ast.AssignExpr {

vlib/v/gen/cgen.v

@@ -282,9 +282,12 @@ fn (g mut Gen) stmt(node ast.Stmt) {
 				g.write('; $i < ')
 				g.expr(it.high)
 				g.writeln('; $i++) { ')
+				g.writeln('int $it.val_var = $i;')
 				g.stmts(it.stmts)
 				g.writeln('}')
 			}
+			//TODO:
+			else {}
 		}
 		ast.ForStmt {
 			g.write('while (')
@@ -569,10 +572,6 @@ fn (g mut Gen) expr(node ast.Expr) {
 				g.expr(it.expr)
 				g.write('.obj')
 			}
-			else {
-				g.write('/* as */ ($styp)')
-				g.expr(it.expr)
-			}
 		}
 		ast.AssignExpr {
 			if ast.expr_is_blank_ident(it.left) {

vlib/v/parser/parser.v

@@ -827,11 +827,13 @@ pub fn (p mut Parser) expr(precedence int) ast.Expr {
 			node = p.index_expr(node)
 		}
 		else if p.tok.kind == .key_as {
+			pos := p.tok.position()
 			p.next()
 			typ = p.parse_type()
 			node = ast.AsCast{
 				expr: node
 				typ: typ
+				pos: pos
 			}
 		}
 		// TODO: handle in later stages since this
@@ -1036,11 +1038,11 @@ fn (p mut Parser) enum_val() ast.EnumVal {
 
 fn (p mut Parser) for_statement() ast.Stmt {
 	p.check(.key_for)
+	pos := p.tok.position()
 	p.open_scope()
 	// defer { p.close_scope() }
 	// Infinite loop
 	if p.tok.kind == .lcbr {
-		pos := p.tok.position()
 		stmts := p.parse_block()
 		p.close_scope()
 		return ast.ForStmt{
@@ -1092,6 +1094,7 @@ fn (p mut Parser) for_statement() ast.Stmt {
 			init: init
 			cond: cond
 			inc: inc
+			pos: pos
 		}
 	}
 	// `for i in vals`, `for i in start .. end`
@@ -1135,12 +1138,12 @@ fn (p mut Parser) for_statement() ast.Stmt {
 		p.close_scope()
 		return ast.ForInStmt{
 			stmts: stmts
-			pos: p.tok.position()
 			cond: cond
 			key_var: key_var_name
 			val_var: val_var_name
 			high: high_expr
 			is_range: is_range
+			pos: pos
 		}
 	}
 	// `for cond {`
@@ -1150,7 +1153,7 @@ fn (p mut Parser) for_statement() ast.Stmt {
 	return ast.ForStmt{
 		cond: cond
 		stmts: stmts
-		pos: p.tok.position()
+		pos: pos
 	}
 }