Fix invalid column math

Author: brandtbucher

Python/compile.c

@@ -4737,7 +4737,19 @@ update_location_to_match_attr(struct compiler *c, expr_ty meth)
     if (meth->lineno != meth->end_lineno) {
         // Make start location match attribute
         c->u->u_loc.lineno = meth->end_lineno;
-        c->u->u_loc.col_offset = meth->end_col_offset - (int)PyUnicode_GetLength(meth->v.Attribute.attr)-1;
+        int len = (int)PyUnicode_GET_LENGTH(meth->v.Attribute.attr);
+        // The dot may or not be on this line. Don't try to include it in the
+        // column span, it's more trouble than it's worth:
+        if (len <= meth->end_col_offset) {
+            //        |---- end_col_offset
+            // .method(...)
+            //  |---------- new col_offset
+            c->u->u_loc.col_offset = meth->end_col_offset - len;
+        }
+        else {
+            // GH-94694: Somebody's compiling weird ASTs. Just drop the columns:
+            c->u->u_loc.col_offset = c->u->u_loc.end_col_offset = -1;
+        }
     }
 }