[3.14] gh-139640: Fix swallowing syntax warnings in different modules (GH-139755) (GH-140117)

Revert GH-131993.

Fix swallowing some syntax warnings in different modules if they accidentally
have the same message and are emitted from the same line.

Fix duplicated warnings in the "finally" block.

(cherry picked from commit 279db6bede)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

* Update 2025-10-06-10-03-37.gh-issue-139640.gY5oTb.rst

---------

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Python/compile.c

@@ -103,6 +103,7 @@ typedef struct _PyCompiler {
     bool c_save_nested_seqs;     /* if true, construct recursive instruction sequences
                                   * (including instructions for nested code objects)
                                   */
+    int c_disable_warning;
 } compiler;
 
 static int
@@ -765,6 +766,9 @@ _PyCompile_PushFBlock(compiler *c, location loc,
     f->fb_loc = loc;
     f->fb_exit = exit;
     f->fb_datum = datum;
+    if (t == COMPILE_FBLOCK_FINALLY_END) {
+        c->c_disable_warning++;
+    }
     return SUCCESS;
 }
 
@@ -776,6 +780,9 @@ _PyCompile_PopFBlock(compiler *c, fblocktype t, jump_target_label block_label)
     u->u_nfblocks--;
     assert(u->u_fblock[u->u_nfblocks].fb_type == t);
     assert(SAME_JUMP_TARGET_LABEL(u->u_fblock[u->u_nfblocks].fb_block, block_label));
+    if (t == COMPILE_FBLOCK_FINALLY_END) {
+        c->c_disable_warning--;
+    }
 }
 
 fblockinfo *
@@ -1203,6 +1210,9 @@ _PyCompile_Error(compiler *c, location loc, const char *format, ...)
 int
 _PyCompile_Warn(compiler *c, location loc, const char *format, ...)
 {
+    if (c->c_disable_warning) {
+        return 0;
+    }
     va_list vargs;
     va_start(vargs, format);
     PyObject *msg = PyUnicode_FromFormatV(format, vargs);