pep-0492: Explain why "async def" and not "def async".

pep-0492.txt

@@ -884,6 +884,22 @@ stating that the statement is asynchronous.  It is also more consistent
 with the existing grammar.
 
 
+Why "async def" and not "def async"
+-----------------------------------
+
+``async`` keyword is a *statement qualifier*.  A good analogy to it are
+"static", "public", "unsafe" keywords from other languages.  "async
+for" is an asynchronous "for" statement, "async with" is an
+asynchronous "with" statement, "async def" is an asynchronous function.
+
+Having "async" after the main statement keyword might introduce some
+confusion, like "for async item in iterator" can be read as "for each
+asynchronous item in iterator".
+
+Also, "async def" better separates coroutines from regular functions
+visually.
+
+
 Why not a __future__ import
 ---------------------------