Fixed false negative in parsing incomplete 'raise ... from' expression (PY-6734)

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

@@ -340,7 +340,9 @@ public class StatementParsing extends Parsing implements ITokenTypeRemapper {
       }
       else if (myBuilder.getTokenType() == PyTokenTypes.FROM_KEYWORD) {
         myBuilder.advanceLexer();
-        getExpressionParser().parseSingleExpression(false);
+        if (!getExpressionParser().parseSingleExpression(false)) {
+          myBuilder.error("Expression expected");
+        }
       }
     }
     checkEndOfStatement(inSuite);

python/testData/psi/RaiseFromNoExpr.py

@@ -0,0 +1,2 @@
+def f():
+    raise AttributeError from

python/testData/psi/RaiseFromNoExpr.txt

@@ -0,0 +1,20 @@
+PyFile:RaiseFromNoExpr.py
+  PyFunction('f')
+    PsiElement(Py:DEF_KEYWORD)('def')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:IDENTIFIER)('f')
+    PyParameterList
+      PsiElement(Py:LPAR)('(')
+      PsiElement(Py:RPAR)(')')
+    PsiElement(Py:COLON)(':')
+    PsiWhiteSpace('\n    ')
+    PyStatementList
+      PyRaiseStatement
+        PsiElement(Py:RAISE_KEYWORD)('raise')
+        PsiWhiteSpace(' ')
+        PyReferenceExpression: AttributeError
+          PsiElement(Py:IDENTIFIER)('AttributeError')
+        PsiWhiteSpace(' ')
+        PsiElement(Py:FROM_KEYWORD)('from')
+        PsiErrorElement:Expression expected
+          <empty list>

python/testSrc/com/jetbrains/python/PythonParsingTest.java

@@ -328,6 +328,11 @@ public class PythonParsingTest extends ParsingTestCase {
     doTest(LanguageLevel.PYTHON33);
   }
 
+  // PY-6734
+  public void testRaiseFromNoExpr() {
+    doTest(LanguageLevel.PYTHON30);
+  }
+
   public void doTest() {
     doTest(LanguageLevel.PYTHON25);
   }