Allow await inside of f-strings (GH-3070)

Cython/Compiler/Scanning.pxd

@@ -33,7 +33,7 @@ cdef class PyrexScanner(Scanner):
     cdef public list indentation_stack
     cdef public indentation_char
     cdef public int bracket_nesting_level
-    cdef bint async_enabled
+    cdef readonly bint async_enabled
     cdef public sy
     cdef public systring
 

Cython/Compiler/Scanning.py

@@ -303,12 +303,25 @@ class PyrexScanner(Scanner):
     def __init__(self, file, filename, parent_scanner=None,
                  scope=None, context=None, source_encoding=None, parse_comments=True, initial_pos=None):
         Scanner.__init__(self, get_lexicon(), file, filename, initial_pos)
+
+        if filename.is_python_file():
+            self.in_python_file = True
+            self.keywords = set(py_reserved_words)
+        else:
+            self.in_python_file = False
+            self.keywords = set(pyx_reserved_words)
+
+        self.async_enabled = 0
+
         if parent_scanner:
             self.context = parent_scanner.context
             self.included_files = parent_scanner.included_files
             self.compile_time_env = parent_scanner.compile_time_env
             self.compile_time_eval = parent_scanner.compile_time_eval
             self.compile_time_expr = parent_scanner.compile_time_expr
+
+            if parent_scanner.async_enabled:
+                self.enter_async()
         else:
             self.context = context
             self.included_files = scope.included_files
@@ -319,17 +332,11 @@ class PyrexScanner(Scanner):
                 self.compile_time_env.update(context.options.compile_time_env)
         self.parse_comments = parse_comments
         self.source_encoding = source_encoding
-        if filename.is_python_file():
-            self.in_python_file = True
-            self.keywords = set(py_reserved_words)
-        else:
-            self.in_python_file = False
-            self.keywords = set(pyx_reserved_words)
         self.trace = trace_scanner
         self.indentation_stack = [0]
         self.indentation_char = None
         self.bracket_nesting_level = 0
-        self.async_enabled = 0
+
         self.begin('INDENT')
         self.sy = ''
         self.next()

tests/run/fstring.pyx

@@ -513,3 +513,21 @@ def percent_s_unicode(u, int i):
     x\u0194z-12
     """
     return u"%s-%d" % (u, i)
+
+
+########################################
+# await inside f-string
+
+def test_await_inside_f_string():
+    """
+    >>> test_await_inside_f_string()
+    PARSED_SUCCESSFULLY
+    """
+
+    async def f():
+        return "some value"
+
+    async def main():
+        print(f"{await f()}")
+
+    print("PARSED_SUCCESSFULLY")