Add test of escape characters

Summary: Our escape characters are not implemented as per the Starlark spec, and the Starlark spec isn't very complete. I've raised bazelbuild/starlark#160 to get more details in the spec, but the temptation is to just follow the Python character escaping spec.

Reviewed By: bobyangyf

Differential Revision: D26276328

fbshipit-source-id: c50a2a677707257a9b481a45a65343cd109cf715

starlark/src/eval/tests.rs

@@ -1092,6 +1092,21 @@ assert_eq(r, [1,2,3,4,5])
     );
 }
 
+#[test]
+// FIXME: All of these tests are broken with either compile-time or runtime failures.
+// Our lexing needs some work.
+#[ignore]
+fn test_escape_characters() {
+    assert_eq!(
+        assert::pass(r#"'\a\b\f\n\r\t\v'"#).to_string(),
+        "\x07\x08\x0C\x0A\x0D\x09\x0B"
+    );
+    assert_eq!(assert::pass(r#"\0"#).to_string(), "\x00");
+    assert_eq!(assert::pass(r#"\12"#).to_string(), "\n");
+    assert_eq!(assert::pass(r#"\101-\132"#).to_string(), "A-Z");
+    assert_eq!(assert::pass(r#"\119"#).to_string(), "\t9");
+}
+
 #[test]
 fn test_deallocation() {
     // Check that we really do deallocate values we create