bpo-38605: Make 'from __future__ import annotations' the default (GH-20434)

The hard part was making all the tests pass; there are some subtle issues here, because apparently the future import wasn't tested very thoroughly in previous Python versions.

For example, `inspect.signature()` returned type objects normally (except for forward references), but strings with the future import. We changed it to try and return type objects by calling `typing.get_type_hints()`, but fall back on returning strings if that function fails (which it may do if there are future references in the annotations that require passing in a specific namespace to resolve).

1 files changed, 2 insertions, 12 deletions

diff --git a/Python/compile.c b/Python/compile.c
index f2563d7..ddd2a04 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -2026,12 +2026,7 @@ compiler_visit_argannotation(struct compiler *c, identifier id,
 {
     if (annotation) {
         PyObject *mangled;
-        if (c->c_future->ff_features & CO_FUTURE_ANNOTATIONS) {
-            VISIT(c, annexpr, annotation)
-        }
-        else {
-            VISIT(c, expr, annotation);
-        }
+        VISIT(c, annexpr, annotation);
         mangled = _Py_Mangle(c->u->u_private, id);
         if (!mangled)
             return 0;
@@ -5261,12 +5256,7 @@ compiler_annassign(struct compiler *c, stmt_ty s)
         if (s->v.AnnAssign.simple &&
             (c->u->u_scope_type == COMPILER_SCOPE_MODULE ||
              c->u->u_scope_type == COMPILER_SCOPE_CLASS)) {
-            if (c->c_future->ff_features & CO_FUTURE_ANNOTATIONS) {
-                VISIT(c, annexpr, s->v.AnnAssign.annotation)
-            }
-            else {
-                VISIT(c, expr, s->v.AnnAssign.annotation);
-            }
+            VISIT(c, annexpr, s->v.AnnAssign.annotation);
             ADDOP_NAME(c, LOAD_NAME, __annotations__, names);
             mangled = _Py_Mangle(c->u->u_private, targ->v.Name.id);
             ADDOP_LOAD_CONST_NEW(c, mangled);