Tokenizer: It should not be possible to break out of backslashes on the next line, even if it was an error

parso/python/tokenize.py

@@ -549,7 +549,7 @@ def tokenize_lines(lines, version_info, start_pos=(1, 0), indents=None, is_first
                     or (initial == '.' and token != '.' and token != '...')):
                 yield PythonToken(NUMBER, token, spos, prefix)
             elif pseudomatch.group(3) is not None:            # ordinary name
-                if token in always_break_tokens:
+                if token in always_break_tokens and (fstring_stack or paren_level):
                     fstring_stack[:] = []
                     paren_level = 0
                     # We only want to dedent if the token is on a new line.

test/test_diff_parser.py

@@ -1585,3 +1585,27 @@ def test_byte_order_mark(differ):
         ''')
     differ.initialize('\n')
     differ.parse(code3, parsers=2, expect_error_leaves=True)
+
+
+def test_backslash_insertion(differ):
+    code1 = dedent('''
+        def f():
+            x
+            def g():
+                base = "" \\
+                       ""
+                return
+        ''')
+    code2 = dedent('''
+        def f():
+            x
+            def g():
+                base = "" \\
+        def h():
+                       ""
+                return
+        ''')
+
+    differ.initialize(code1)
+    differ.parse(code2, parsers=2, copies=1, expect_error_leaves=True)
+    differ.parse(code1, parsers=2, copies=1)

test/test_tokenize.py

@@ -263,6 +263,7 @@ xfail_py2 = dict(marks=[pytest.mark.xfail(sys.version_info[0] == 2, reason='Pyth
         ('  )\n foo', [INDENT, OP, NEWLINE, ERROR_DEDENT, NAME, DEDENT]),
         ('a\n b\n  )\n c', [NAME, NEWLINE, INDENT, NAME, NEWLINE, INDENT, OP,
                             NEWLINE, DEDENT, NAME, DEDENT]),
+        (' 1 \\\ndef', [INDENT, NUMBER, NAME, DEDENT]),
     ]
 )
 def test_token_types(code, types):
@@ -343,7 +344,7 @@ def test_form_feed():
 
 def test_carriage_return():
     lst = _get_token_list(' =\\\rclass')
-    assert [t.type for t in lst] == [INDENT, OP, DEDENT, NAME, ENDMARKER]
+    assert [t.type for t in lst] == [INDENT, OP, NAME, DEDENT, ENDMARKER]
 
 
 def test_backslash():