report missing value expression in dict literal as error (PY-2791)

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

@@ -219,6 +219,7 @@ public class ExpressionParsing extends Parsing {
     }
     checkMatches(PyTokenTypes.COLON, message("PARSE.expected.colon"));
     if (!parseSingleExpression(false)) {
+      myBuilder.error("value expression expected");
       marker.drop();
       return false;
     }

python/testData/psi/DictMissingValue.py

@@ -0,0 +1 @@
+dl = {key1: value1, key2:}

python/testData/psi/DictMissingValue.txt

@@ -0,0 +1,24 @@
+PyFile:DictMissingValue.py
+  PyAssignmentStatement
+    PyTargetExpression: dl
+      PsiElement(Py:IDENTIFIER)('dl')
+    PsiWhiteSpace(' ')
+    PsiElement(Py:EQ)('=')
+    PsiWhiteSpace(' ')
+    PyDictLiteralExpression
+      PsiElement(Py:LBRACE)('{')
+      PyKeyValueExpression
+        PyReferenceExpression: key1
+          PsiElement(Py:IDENTIFIER)('key1')
+        PsiElement(Py:COLON)(':')
+        PsiWhiteSpace(' ')
+        PyReferenceExpression: value1
+          PsiElement(Py:IDENTIFIER)('value1')
+      PsiElement(Py:COMMA)(',')
+      PsiWhiteSpace(' ')
+      PyReferenceExpression: key2
+        PsiElement(Py:IDENTIFIER)('key2')
+      PsiElement(Py:COLON)(':')
+      PsiErrorElement:value expression expected
+        <empty list>
+      PsiElement(Py:RBRACE)('}')

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

@@ -247,6 +247,10 @@ public class PythonParsingTest extends ParsingTestCase {
     doTest();
   }
 
+  public void testDictMissingValue() {  // PY-2791
+    doTest();
+  }
+
   public void doTest() {
     doTest(LanguageLevel.PYTHON25);
   }