Better error recovery for lines with single 'class' or 'def' keywords and normal functions defined below

python/testData/psi/KeywordAsFunctionName.txt

@@ -2,7 +2,7 @@ PyFile:KeywordAsFunctionName.py
   PyFunction('null')
     PsiElement(Py:DEF_KEYWORD)('def')
     PsiWhiteSpace(' ')
-    PsiErrorElement:function name expected
+    PsiErrorElement:Identifier expected
       PsiElement(Py:FROM_KEYWORD)('from')
     PyParameterList
       PsiElement(Py:LPAR)('(')

python/testData/psi/SingleClassBeforeFunction.py

@@ -0,0 +1,5 @@
+class
+
+
+def foo():
+    pass

python/testData/psi/SingleClassBeforeFunction.txt

@@ -0,0 +1,25 @@
+PyFile:SingleClassBeforeFunction.py
+  PyClass: null
+    PsiElement(Py:CLASS_KEYWORD)('class')
+    PsiErrorElement:Identifier expected
+      <empty list>
+    PyArgumentList
+      <empty list>
+    PsiErrorElement:Colon expected
+      <empty list>
+    PsiWhiteSpace('\n\n\n')
+    PyStatementList
+      PsiErrorElement:Indent expected
+        <empty list>
+  PyFunction('foo')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:IDENTIFIER)('foo')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyPassStatement
+        PsiElement(Py:PASS_KEYWORD)('pass')

python/testData/psi/SingleDefBeforeFunction.py

@@ -0,0 +1,5 @@
+def
+
+
+def bar():
+    x = 1

python/testData/psi/SingleDefBeforeFunction.txt

@@ -0,0 +1,31 @@
+PyFile:SingleDefBeforeFunction.py
+  PyFunction('null')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiErrorElement:Identifier expected
+      <empty list>
+    PsiErrorElement:'(' expected
+      <empty list>
+    PyParameterList
+      <empty list>
+    PsiWhiteSpace('\n\n\n')
+    PyStatementList
+      PsiErrorElement:Indent expected
+        <empty list>
+  PyFunction('bar')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:IDENTIFIER)('bar')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyAssignmentStatement
+        PyTargetExpression: x
+          PsiElement(Py:IDENTIFIER)('x')
+        PsiWhiteSpace(' ')
+        PsiElement(Py:EQ)('=')
+        PsiWhiteSpace(' ')
+        PyNumericLiteralExpression
+          PsiElement(Py:INTEGER_LITERAL)('1')