Added some text about escaping quote chars, and about raw f-strings.

pep-0498.txt

@@ -183,9 +183,9 @@ for strings should be trivially modifiable to recognize f-strings
 (parsing within an f-string is another matter, of course).
 
 Once tokenized, f-strings are decoded. This will convert backslash
-escapes such as ``'\n'``, ``'\xhh'``, ``'\uxxxx'``, ``'\Uxxxxxxxx'``,
-and named unicode characters ``'\N{name}'`` into their associated
-Unicode characters [#]_.
+escapes such as ``'\n'``, ``'\"'``, ``"\'"``, ``'\xhh'``,
+``'\uxxxx'``, ``'\Uxxxxxxxx'``, and named unicode characters
+``'\N{name}'`` into their associated Unicode characters [#]_.
 
 Up to this point, the processing of f-strings and normal strings is
 exactly the same.
@@ -256,6 +256,28 @@ resulting string value is to double the brace::
   >>> f'{{{4*10}}}'
   '{40}'
 
+Like all raw in Python, no escape processing is done for raw
+f-strings::
+
+  >>> fr'x={4*10}\n'
+  'x=40\\n'
+
+Due to Python's string tokenizing rules, the f-string
+``f'abc {a['x']} def'`` is invalid. The tokenizer parses this as 3
+tokens: ``f'abc {a['``, ``x``, and ``']} def'``. Just like regular
+strings, this cannot be fixed by using raw strings. There are a number
+of correct ways to write this f-string: with escaped single quotes::
+
+  f'abc {a[\'x\']} def'
+
+With a different quote character::
+
+  f"abc {a['x']} def"
+
+Or with triple quotes::
+
+  f'''abc {a['x']} def'''
+
 Code equivalence
 ----------------