Fix whole-file ignoring. (#6853)

Fixes #6852, and adds a regression test.

mypy/fastparse.py

@@ -38,6 +38,7 @@
 from mypy import message_registry
 from mypy.errors import Errors
 from mypy.options import Options
+from mypy.reachability import mark_block_unreachable
 
 try:
     # pull this into a final variable to make mypyc be quiet about the
@@ -311,7 +312,7 @@ def translate_stmt_list(self,
                 and min(self.type_ignores) < self.get_lineno(stmts[0])):
             self.errors.used_ignored_lines[self.errors.file].add(min(self.type_ignores))
             block = Block(self.fix_function_overloads(self.translate_stmt_list(stmts)))
-            block.is_unreachable = True
+            mark_block_unreachable(block)
             return [block]
 
         res = []  # type: List[Statement]

mypy/fastparse2.py

@@ -47,6 +47,7 @@
 from mypy.errors import Errors
 from mypy.fastparse import TypeConverter, parse_type_comment, bytes_to_human_readable_repr
 from mypy.options import Options
+from mypy.reachability import mark_block_unreachable
 
 try:
     from typed_ast import ast27
@@ -209,7 +210,7 @@ def translate_stmt_list(self,
                 and min(self.type_ignores) < self.get_lineno(stmts[0])):
             self.errors.used_ignored_lines[self.errors.file].add(min(self.type_ignores))
             block = Block(self.fix_function_overloads(self.translate_stmt_list(stmts)))
-            block.is_unreachable = True
+            mark_block_unreachable(block)
             return [block]
 
         res = []  # type: List[Statement]

test-data/unit/check-ignore.test

@@ -242,6 +242,10 @@ IGNORE
 def f(): ...
 IGNORE
 
+[case testIgnoreWholeModule5]
+# type: ignore
+import MISSING
+
 [case testDontIgnoreWholeModule1]
 if True:
     # type: ignore