cgen: fix `for` iteration over fixed array literal (#8159)

vlib/v/gen/cgen.v

@@ -1278,11 +1278,12 @@ fn (mut g Gen) for_in(it ast.ForInStmt) {
 		atmp := g.new_tmp_var()
 		atmp_type := g.typ(it.cond_type)
 		if !it.cond.is_lvalue() {
-			g.error('for in: unhandled condition `$it.cond`', it.pos)
+			g.write('$atmp_type *$atmp = &(($atmp_type)')
+		} else {
+			g.write('$atmp_type *$atmp = &(')
 		}
-		// TODO rvalue cond
-		g.write('$atmp_type *$atmp = &')
 		g.expr(it.cond)
+		g.writeln(')')
 		g.writeln(';')
 		i := if it.key_var in ['', '_'] { g.new_tmp_var() } else { it.key_var }
 		cond_sym := g.table.get_type_symbol(it.cond_type)

vlib/v/tests/fixed_array_test.v

@@ -68,3 +68,20 @@ fn test_fixed_array_can_be_passed_as_mut_arg() {
 	change_first_element(mut arr2)
 	assert arr2 == [[0,2,3]!, [4,5,6]!, [7,8,9]!]!
 }
+
+fn test_iteration_over_fixed_array() {
+	mut s := u16(0)
+	arr := [u16(3), 2, 17, 23]!
+	for v in arr {
+		s += v
+	}
+	assert s == 45
+}
+
+fn test_iteration_over_fixed_array_literal() {
+	mut s := 0.0
+	for v in [0.5, -2.25, 3.75, 12.0, 13.25]! {
+		s += v
+	}
+	assert s == 27.25
+}