bpo-42246: Don't forget the entry block when ensuring that all exits have a line number (GH-23636)

Don't forget the entry block when ensuring that all exits have a line number.

Lib/test/test_compile.py

@@ -809,6 +809,24 @@ if 1:
                 func(save_caller_frame)
                 self.assertEqual(frame.f_lineno-frame.f_code.co_firstlineno, lastline)
 
+    def test_lineno_after_no_code(self):
+        def no_code1():
+            "doc string"
+
+        def no_code2():
+            a: int
+
+        for func in (no_code1, no_code2):
+            with self.subTest(func=func):
+                code = func.__code__
+                lines = list(code.co_lines())
+                self.assertEqual(len(lines), 1)
+                start, end, line = lines[0]
+                self.assertEqual(start, 0)
+                self.assertEqual(end, len(code.co_code))
+                self.assertEqual(line, code.co_firstlineno)
+
+
     def test_big_dict_literal(self):
         # The compiler has a flushing point in "compiler_dict" that calls compiles
         # a portion of the dictionary literal when the loop that iterates over the items

Python/compile.c

@@ -6514,6 +6514,7 @@ is_exit_without_lineno(basicblock *b) {
 static int
 ensure_exits_have_lineno(struct compiler *c)
 {
+    basicblock *entry = NULL;
     /* Copy all exit blocks without line number that are targets of a jump.
      */
     for (basicblock *b = c->u->u_blocks; b != NULL; b = b->b_list) {
@@ -6535,6 +6536,11 @@ ensure_exits_have_lineno(struct compiler *c)
                 b->b_instr[b->b_iused-1].i_target = new_target;
             }
         }
+        entry = b;
+    }
+    assert(entry != NULL);
+    if (is_exit_without_lineno(entry)) {
+        entry->b_instr[0].i_lineno = c->u->u_firstlineno;
     }
     /* Any remaining reachable exit blocks without line number can only be reached by
      * fall through, and thus can only have a single predecessor */

Python/importlib.h

@@ -1243,7 +1243,7 @@ const unsigned char _Py_M__importlib_bootstrap[] = {
     114,32,109,111,100,117,108,101,32,99,114,101,97,116,105,111,
     110,46,78,114,10,0,0,0,114,161,0,0,0,114,10,0,
     0,0,114,10,0,0,0,114,11,0,0,0,114,150,0,0,
-    0,66,3,0,0,115,4,0,0,0,4,128,255,128,122,28,
+    0,66,3,0,0,115,4,0,0,0,4,0,255,128,122,28,
     70,114,111,122,101,110,73,109,112,111,114,116,101,114,46,99,
     114,101,97,116,101,95,109,111,100,117,108,101,99,1,0,0,
     0,0,0,0,0,0,0,0,0,3,0,0,0,4,0,0,

Python/importlib_external.h

@@ -1153,7 +1153,7 @@ const unsigned char _Py_M__importlib_bootstrap_external[] = {
     0,169,2,114,123,0,0,0,114,191,0,0,0,114,7,0,
     0,0,114,7,0,0,0,114,8,0,0,0,218,13,99,114,
     101,97,116,101,95,109,111,100,117,108,101,55,3,0,0,115,
-    4,0,0,0,4,128,255,128,122,27,95,76,111,97,100,101,
+    4,0,0,0,4,0,255,128,122,27,95,76,111,97,100,101,
     114,66,97,115,105,99,115,46,99,114,101,97,116,101,95,109,
     111,100,117,108,101,99,2,0,0,0,0,0,0,0,0,0,
     0,0,3,0,0,0,5,0,0,0,67,0,0,0,115,56,
@@ -1292,7 +1292,7 @@ const unsigned char _Py_M__importlib_bootstrap_external[] = {
     32,32,32,78,114,7,0,0,0,41,3,114,123,0,0,0,
     114,52,0,0,0,114,37,0,0,0,114,7,0,0,0,114,
     7,0,0,0,114,8,0,0,0,114,232,0,0,0,105,3,
-    0,0,115,4,0,0,0,4,128,255,128,122,21,83,111,117,
+    0,0,115,4,0,0,0,4,0,255,128,122,21,83,111,117,
     114,99,101,76,111,97,100,101,114,46,115,101,116,95,100,97,
     116,97,99,2,0,0,0,0,0,0,0,0,0,0,0,5,
     0,0,0,10,0,0,0,67,0,0,0,115,70,0,0,0,
@@ -2019,7 +2019,7 @@ const unsigned char _Py_M__importlib_bootstrap_external[] = {
     0,115,4,0,0,0,100,1,83,0,114,217,0,0,0,114,
     7,0,0,0,114,218,0,0,0,114,7,0,0,0,114,7,
     0,0,0,114,8,0,0,0,114,219,0,0,0,217,4,0,
-    0,115,4,0,0,0,4,128,255,128,122,30,95,78,97,109,
+    0,115,4,0,0,0,4,0,255,128,122,30,95,78,97,109,
     101,115,112,97,99,101,76,111,97,100,101,114,46,99,114,101,
     97,116,101,95,109,111,100,117,108,101,99,2,0,0,0,0,
     0,0,0,0,0,0,0,2,0,0,0,1,0,0,0,67,