cgen: fix error for struct with reference alias field (#13380)

vlib/v/gen/c/auto_str_methods.v

@@ -916,7 +916,8 @@ fn (mut g Gen) gen_str_for_struct(info ast.Struct, styp string, str_fn_name stri
 			funcprefix += 'isnil(it.${c_name(field.name)})'
 			funcprefix += ' ? _SLIT("nil") : '
 			// struct, floats and ints have a special case through the _str function
-			if sym.kind != .struct_ && !field.typ.is_int_valptr() && !field.typ.is_float_valptr() {
+			if sym.kind !in [.struct_, .alias] && !field.typ.is_int_valptr()
+				&& !field.typ.is_float_valptr() {
 				funcprefix += '*'
 			}
 		}

vlib/v/gen/c/cgen.v

@@ -4530,6 +4530,12 @@ fn (mut g Gen) cast_expr(node ast.CastExpr) {
 			g.gen_optional_error(node.typ, node.expr)
 		} else {
 			g.write('(${cast_label}(')
+			if sym.kind == .alias && g.table.final_sym(node.typ).kind == .string {
+				ptr_cnt := node.typ.nr_muls() - node.expr_type.nr_muls()
+				if ptr_cnt > 0 {
+					g.write('&'.repeat(ptr_cnt))
+				}
+			}
 			g.expr(node.expr)
 			if node.expr is ast.IntegerLiteral {
 				if node.typ in [ast.u64_type, ast.u32_type, ast.u16_type] {

vlib/v/gen/c/str.v

@@ -85,6 +85,9 @@ fn (mut g Gen) gen_expr_to_string(expr ast.Expr, etype ast.Type) {
 		g.expr(expr)
 		g.write(')')
 	} else if typ == ast.string_type {
+		if etype.is_ptr() {
+			g.write('*')
+		}
 		g.expr(expr)
 	} else if typ == ast.bool_type {
 		g.expr(expr)

vlib/v/tests/struct_with_reference_alias_field.v

@@ -0,0 +1,13 @@
+type SS = string
+
+struct ST {
+	data &SS
+}
+
+fn test_struct_with_reference_alias_fields() {
+	mut val := ST{
+		data: &SS('hi')
+	}
+	println(val.data)
+	assert '$val.data' == 'hi'
+}