From 40bc05ee1eafcc2f0b3ed48f212a1526b65163bc Mon Sep 17 00:00:00 2001
From: Josh Klar <josh@klar.sh>
Date: Thu, 26 Sep 2019 16:48:02 -0700
Subject: [PATCH] Address dpgeorge feedback - largely simplifications

---
 py/lexer.c                            | 26 +++++++++-----------------
 py/parse.c                            | 12 ++++++++++++
 tests/basics/string_pep498_fstring.py | 13 -------------
 3 files changed, 21 insertions(+), 30 deletions(-)

diff --git a/py/lexer.c b/py/lexer.c
index 6894ada47..c3f4e6506 100644
--- a/py/lexer.c
+++ b/py/lexer.c
@@ -129,29 +129,21 @@ STATIC bool is_tail_of_identifier(mp_lexer_t *lex) {
 
 STATIC void swap_char_banks(mp_lexer_t *lex) {
     if (lex->vstr_postfix_processing) {
-        unichar h0, h1, h2;
-
-        h0 = lex->chr0;
-        h1 = lex->chr1;
-        h2 = lex->chr2;
-
-        lex->chr0 = lex->vstr_postfix.len > 0 ? lex->vstr_postfix.buf[0] : 0;
-        lex->chr1 = lex->vstr_postfix.len > 1 ? lex->vstr_postfix.buf[1] : 0;
-        lex->chr2 = lex->vstr_postfix.len > 2 ? lex->vstr_postfix.buf[2] : 0;
-        lex->chr3 = h0;
-        lex->chr4 = h1;
-        lex->chr5 = h2;
-
-        lex->vstr_postfix_idx = lex->vstr_postfix.len > 2 ? 3 : lex->vstr_postfix.len;
+        lex->chr3 = lex->chr0;
+        lex->chr4 = lex->chr1;
+        lex->chr5 = lex->chr2;
+        lex->chr0 = lex->vstr_postfix.buf[0];
+        lex->chr1 = lex->vstr_postfix.buf[1];
+        lex->chr2 = lex->vstr_postfix.buf[2];
+
+        lex->vstr_postfix_idx = 3;
     } else {
         // blindly reset to the "backup" bank when done postfix processing
         // this restores control to the mp_reader
         lex->chr0 = lex->chr3;
         lex->chr1 = lex->chr4;
         lex->chr2 = lex->chr5;
-        lex->chr3 = 0;
-        lex->chr4 = 0;
-        lex->chr5 = 0;
+        // willfully ignoring setting chr3-5 here - WARNING consider those garbage data now
 
         vstr_reset(&lex->vstr_postfix);
         lex->vstr_postfix_idx = 0;
diff --git a/py/parse.c b/py/parse.c
index d30d1b22f..f86ee25fe 100644
--- a/py/parse.c
+++ b/py/parse.c
@@ -1178,6 +1178,7 @@ mp_parse_tree_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind) {
                 exc = mp_obj_new_exception_msg(&mp_type_IndentationError,
                     translate("unindent does not match any outer indentation level"));
                 break;
+#if MICROPY_ERROR_REPORTING == MICROPY_ERROR_REPORTING_DETAILED
             case MP_TOKEN_FSTRING_BACKSLASH:
                 exc = mp_obj_new_exception_msg(&mp_type_SyntaxError,
                     translate("f-string expression part cannot include a backslash"));
@@ -1202,6 +1203,17 @@ mp_parse_tree_t mp_parse(mp_lexer_t *lex, mp_parse_input_kind_t input_kind) {
                 exc = mp_obj_new_exception_msg(&mp_type_NotImplementedError,
                     translate("raw f-strings are not implemented"));
                 break;
+#else
+            case MP_TOKEN_FSTRING_BACKSLASH:
+            case MP_TOKEN_FSTRING_COMMENT:
+            case MP_TOKEN_FSTRING_UNCLOSED:
+            case MP_TOKEN_FSTRING_UNOPENED:
+            case MP_TOKEN_FSTRING_EMPTY_EXP:
+            case MP_TOKEN_FSTRING_RAW:
+                exc = mp_obj_new_exception_msg(&mp_type_SyntaxError,
+                    translate("malformed f-string"));
+                break;
+#endif
             default:
                 exc = mp_obj_new_exception_msg(&mp_type_SyntaxError,
                     translate("invalid syntax"));
diff --git a/tests/basics/string_pep498_fstring.py b/tests/basics/string_pep498_fstring.py
index f1ad1f19b..f4e76c831 100644
--- a/tests/basics/string_pep498_fstring.py
+++ b/tests/basics/string_pep498_fstring.py
@@ -111,16 +111,3 @@ assert ('a' 'b' f'{x}' f'str<{y:^4}>' 'd' 'e') == 'ab10str< hi >de'
 
 # Other tests
 assert f'{{{4*10}}}' == '{40}'
-
-try:
-    eval("fr''")
-except NotImplementedError:
-    pass
-else:
-    raise RuntimeError('expected raw f-string to raise NotImplementedError')
-try:
-    eval("rf''")
-except NotImplementedError:
-    pass
-else:
-    raise RuntimeError('expected raw f-string to raise NotImplementedError')