Merge branch 'nested-function-none-init'

Partially addresses #649.

Author: JukkaL

mypy/semanal.py

@@ -221,6 +221,12 @@ def visit_func_def(self, defn: FuncDef) -> None:
 
         defn.is_conditional = self.block_depth[-1] > 0
 
+        # TODO(jukka): Figure out how to share the various cases. It doesn't
+        #   make sense to have (almost) duplicate code (here and elsewhere) for
+        #   3 cases: module-level, class-level and local names. Maybe implement
+        #   a common stack of namespaces. As the 3 kinds of namespaces have
+        #   different semantics, this wouldn't always work, but it might still
+        #   be a win.
         if self.is_class_scope():
             # Method definition
             defn.info = self.type
@@ -237,7 +243,15 @@ def visit_func_def(self, defn: FuncDef) -> None:
         elif self.is_func_scope():
             # Nested function
             if not defn.is_decorated and not defn.is_overload:
-                self.add_local(defn, defn)
+                if defn.name() in self.locals[-1]:
+                    # Redefinition. Conditional redefinition is okay.
+                    n = self.locals[-1][defn.name()].node
+                    if self.is_conditional_func(n, defn):
+                        defn.original_def = cast(FuncDef, n)
+                    else:
+                        self.name_already_defined(defn.name(), defn)
+                else:
+                    self.add_local(defn, defn)
         else:
             # Top-level function
             if not defn.is_decorated and not defn.is_overload:
@@ -2026,11 +2040,14 @@ def enter(self) -> None:
         self.locals.append(SymbolTable())
         self.global_decls.append(set())
         self.nonlocal_decls.append(set())
+        # -1 since entering block will increment this to 0.
+        self.block_depth.append(-1)
 
     def leave(self) -> None:
         self.locals.pop()
         self.global_decls.pop()
         self.nonlocal_decls.pop()
+        self.block_depth.pop()
 
     def is_func_scope(self) -> bool:
         return self.locals[-1] is not None

mypy/test/data/check-functions.test

@@ -866,6 +866,27 @@ main:9: error: Unsupported left operand type for + ("int")
 main: note: At top level:
 main:12: error: Argument 1 to "f" has incompatible type "str"; expected "int"
 
+[case testNestedConditionalFunctionDefinitionWithIfElse]
+from typing import Any
+x = None # type: Any
+def top() -> None:
+    if x:
+        def f(x: int) -> None:
+            x = 'x'   # fail
+            x = 1
+    else:
+        def f(x: int) -> None:
+            x + 'x'   # fail
+            x = 1
+    f(1)
+    f('x') # fail
+[out]
+main: note: In function "f":
+main:6: error: Incompatible types in assignment (expression has type "str", variable has type "int")
+main:10: error: Unsupported left operand type for + ("int")
+main: note: In function "top":
+main:13: error: Argument 1 to "f" has incompatible type "str"; expected "int"
+
 [case testUnconditionalRedefinitionOfConditionalFunction]
 from typing import Any
 x = None # type: Any
@@ -929,6 +950,17 @@ if g():
 f()
 f(1) # E: Too many arguments for "f"
 
+[case testRedefineNestedFunctionDefinedAsVariableInitializedToNone]
+def g() -> None:
+    f = None
+    if object():
+        def f(x: int) -> None: pass
+    f() # E: Too few arguments for "f"
+    f(1)
+    f('') # E: Argument 1 to "f" has incompatible type "str"; expected "int"
+[out]
+main: note: In function "g":
+
 [case testRedefineFunctionDefinedAsVariableWithInvalidSignature]
 def g(): pass
 f = g