Fix #1082 -- internal error when updating partial type from outer scope.

Author: Guido van Rossum

mypy/checkexpr.py

@@ -75,8 +75,9 @@ def analyze_ref_expr(self, e: RefExpr) -> Type:
             result = self.analyze_var_ref(node, e)
             if isinstance(result, PartialType):
                 partial_types = self.chk.partial_types[-1]
-                context = partial_types[node]
-                self.msg.fail(messages.NEED_ANNOTATION_FOR_VAR, context)
+                if node in partial_types:
+                    context = partial_types[node]
+                    self.msg.fail(messages.NEED_ANNOTATION_FOR_VAR, context)
                 result = AnyType()
         elif isinstance(node, FuncDef):
             # Reference to a global function.

mypy/test/data/check-inference.test

@@ -1191,6 +1191,13 @@ b[{}] = 1
 [builtins fixtures/dict.py]
 [out]
 
+[case testInferDictInitializedToEmptyAndUpdatedFromMethod]
+map = {}  # E: Need type annotation for variable
+def add():
+    map[1] = 2
+[builtins fixtures/dict.py]
+[out]
+
 [case testSpecialCaseEmptyListInitialization]
 def f(blocks: Any): # E: Name 'Any' is not defined
     to_process = [] # E: Need type annotation for variable