Assignment to await expressions is forbidden now

python/src/com/jetbrains/python/parsing/ExpressionParsing.java

@@ -972,12 +972,21 @@ public class ExpressionParsing extends Parsing {
 
   private boolean parseAwaitExpression(boolean isTargetExpression) {
     if (atToken(PyTokenTypes.AWAIT_KEYWORD)) {
-      PsiBuilder.Marker expr = myBuilder.mark();
+      final PsiBuilder.Marker expr = myBuilder.mark();
       myBuilder.advanceLexer();
+
       if (!parseMemberExpression(isTargetExpression)) {
         myBuilder.error(message("PARSE.expected.expression"));
+        expr.done(PyElementTypes.PREFIX_EXPRESSION);
       }
-      expr.done(PyElementTypes.PREFIX_EXPRESSION);
+      else {
+        if (isTargetExpression) {
+          expr.error("can't assign to await expression");
+        } else {
+          expr.done(PyElementTypes.PREFIX_EXPRESSION);
+        }
+      }
+
       return true;
     }
     else {

python/testData/psi/Await.py

@@ -2,4 +2,9 @@ async def f(x):
     await x
 
 
+async def g(y):
+    await x = 5
+    await y
+
+
 await = 1

python/testData/psi/Await.txt

@@ -20,6 +20,39 @@ PyFile:Await.py
           PyReferenceExpression: x
             PsiElement(Py:IDENTIFIER)('x')
   PsiWhiteSpace('\n\n\n')
+  PyFunction('g')
+    PsiElement(Py:ASYNC_KEYWORD)('async')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:IDENTIFIER)('g')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PyNamedParameter('y')
+        PsiElement(Py:IDENTIFIER)('y')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyAssignmentStatement
+        PsiErrorElement:can't assign to await expression
+          PsiElement(Py:AWAIT_KEYWORD)('await')
+          PsiWhiteSpace(' ')
+          PyTargetExpression: x
+            PsiElement(Py:IDENTIFIER)('x')
+        PsiWhiteSpace(' ')
+        PsiElement(Py:EQ)('=')
+        PsiWhiteSpace(' ')
+        PyNumericLiteralExpression
+          PsiElement(Py:INTEGER_LITERAL)('5')
+      PsiWhiteSpace('\n    ')
+      PyExpressionStatement
+        PyPrefixExpression
+          PsiElement(Py:AWAIT_KEYWORD)('await')
+          PsiWhiteSpace(' ')
+          PyReferenceExpression: y
+            PsiElement(Py:IDENTIFIER)('y')
+  PsiWhiteSpace('\n\n\n')
   PyAssignmentStatement
     PyTargetExpression: await
       PsiElement(Py:IDENTIFIER)('await')