stage2: implement @truncate

test/behavior/basic.zig

@@ -1,3 +1,6 @@
+const std = @import("std");
+const expect = std.testing.expect;
+
 // normal comment
 
 /// this is a documentation comment
@@ -7,3 +10,11 @@ fn emptyFunctionWithComments() void {}
 test "empty function with comments" {
     emptyFunctionWithComments();
 }
+
+test "truncate" {
+    try expect(testTruncate(0x10fd) == 0xfd);
+    comptime try expect(testTruncate(0x10fd) == 0xfd);
+}
+fn testTruncate(x: u32) u8 {
+    return @truncate(u8, x);
+}