From a8b0dfb38ada784c454114c53a423e2082a355a0 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@vlang.io>
Date: Thu, 25 Jun 2020 14:55:53 +0200
Subject: [PATCH] checker: allow casting strings to string aliases

---
 vlib/v/ast/ast.v         |  2 +-
 vlib/v/checker/checker.v | 15 +++++++++------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 8c665187f7..6593f3684d 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -703,7 +703,7 @@ pub struct CastExpr {
 pub:
 	expr      Expr // `buf`
 	arg       Expr // `n` in `string(buf, n)`
-	typ       table.Type // `string`
+	typ       table.Type // `string` TODO rename to `type_to_cast_to`
 	pos       token.Position
 pub mut:
 	typname   string
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 0c5008b255..8b52a5e0b2 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1962,14 +1962,17 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 					node.pos)
 			}
 			if node.expr_type == table.string_type {
-				mut error_msg := 'cannot cast a string'
-				if node.expr is ast.StringLiteral {
-					str_lit := node.expr as ast.StringLiteral
-					if str_lit.val.len == 1 {
-						error_msg += ", for denoting characters use `$str_lit.val` instead of '$str_lit.val'"
+				cast_to_type_sym := c.table.get_type_symbol(node.typ)
+				if cast_to_type_sym.kind != .alias {
+					mut error_msg := 'cannot cast a string'
+					if node.expr is ast.StringLiteral {
+						str_lit := node.expr as ast.StringLiteral
+						if str_lit.val.len == 1 {
+							error_msg += ", for denoting characters use `$str_lit.val` instead of '$str_lit.val'"
+						}
 					}
+					c.error(error_msg, node.pos)
 				}
-				c.error(error_msg, node.pos)
 			}
 			if node.has_arg {
 				c.expr(node.arg)