bpo-43892: Validate the first term of complex literal value patterns (GH-25735)

2 files changed, 20 insertions, 38 deletions

diff --git a/Python/ast_opt.c b/Python/ast_opt.c
index 254dd646c4..c1fdea3a88 100644
--- a/Python/ast_opt.c
+++ b/Python/ast_opt.c
@@ -825,7 +825,7 @@ astfold_pattern(pattern_ty node_, PyArena *ctx_, _PyASTOptimizeState *state)
             break;
         case MatchAs_kind:
             if (node_->v.MatchAs.pattern) {
-                CALL(astfold_pattern, expr_ty, node_->v.MatchAs.pattern);
+                CALL(astfold_pattern, pattern_ty, node_->v.MatchAs.pattern);
             }
             break;
         case MatchOr_kind:
diff --git a/Python/compile.c b/Python/compile.c
index 1349a852a2..6560fd426a 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -5609,6 +5609,10 @@ compiler_slice(struct compiler *c, expr_ty s)
 static int
 pattern_helper_store_name(struct compiler *c, identifier n, pattern_context *pc)
 {
+    if (n == NULL) {
+        ADDOP(c, POP_TOP);
+        return 1;
+    }
     if (forbidden_name(c, n, Store)) {
         return 0;
     }
@@ -5783,41 +5787,22 @@ compiler_pattern_subpattern(struct compiler *c, pattern_ty p, pattern_context *p
 }
 
 static int
-compiler_pattern_capture(struct compiler *c, identifier n, pattern_context *pc)
-{
-    RETURN_IF_FALSE(pattern_helper_store_name(c, n, pc));
-    ADDOP_LOAD_CONST(c, Py_True);
-    return 1;
-}
-
-static int
-compiler_pattern_wildcard(struct compiler *c, pattern_ty p, pattern_context *pc)
-{
-    assert(p->kind == MatchAs_kind);
-    if (!pc->allow_irrefutable) {
-        // Whoops, can't have a wildcard here!
-        const char *e = "wildcard makes remaining patterns unreachable";
-        return compiler_error(c, e);
-    }
-    ADDOP(c, POP_TOP);
-    ADDOP_LOAD_CONST(c, Py_True);
-    return 1;
-}
-
-static int
 compiler_pattern_as(struct compiler *c, pattern_ty p, pattern_context *pc)
 {
     assert(p->kind == MatchAs_kind);
-    if (p->v.MatchAs.name == NULL) {
-        return compiler_pattern_wildcard(c, p, pc);
-    }
     if (p->v.MatchAs.pattern == NULL) {
+        // An irrefutable match:
         if (!pc->allow_irrefutable) {
-            // Whoops, can't have a name capture here!
-            const char *e = "name capture %R makes remaining patterns unreachable";
-            return compiler_error(c, e, p->v.MatchAs.name);
+            if (p->v.MatchAs.name) {
+                const char *e = "name capture %R makes remaining patterns unreachable";
+                return compiler_error(c, e, p->v.MatchAs.name);
+            }
+            const char *e = "wildcard makes remaining patterns unreachable";
+            return compiler_error(c, e);
         }
-        return compiler_pattern_capture(c, p->v.MatchAs.name, pc);
+        RETURN_IF_FALSE(pattern_helper_store_name(c, p->v.MatchAs.name, pc));
+        ADDOP_LOAD_CONST(c, Py_True);
+        return 1;
     }
     basicblock *end, *fail_pop_1;
     RETURN_IF_FALSE(end = compiler_new_block(c));
@@ -5842,12 +5827,9 @@ static int
 compiler_pattern_star(struct compiler *c, pattern_ty p, pattern_context *pc)
 {
     assert(p->kind == MatchStar_kind);
-    if (!pc->allow_irrefutable) {
-        // Whoops, can't have a star capture here!
-        const char *e = "star captures are only allowed as part of sequence patterns";
-        return compiler_error(c, e);
-    }
-    return compiler_pattern_capture(c, p->v.MatchStar.name, pc);
+    RETURN_IF_FALSE(pattern_helper_store_name(c, p->v.MatchStar.name, pc));
+    ADDOP_LOAD_CONST(c, Py_True);
+    return 1;
 }
 
 static int
@@ -6206,7 +6188,7 @@ compiler_pattern_value(struct compiler *c, pattern_ty p, pattern_context *pc)
 }
 
 static int
-compiler_pattern_constant(struct compiler *c, pattern_ty p, pattern_context *pc)
+compiler_pattern_singleton(struct compiler *c, pattern_ty p, pattern_context *pc)
 {
     assert(p->kind == MatchSingleton_kind);
     ADDOP_LOAD_CONST(c, p->v.MatchSingleton.value);
@@ -6222,7 +6204,7 @@ compiler_pattern(struct compiler *c, pattern_ty p, pattern_context *pc)
         case MatchValue_kind:
             return compiler_pattern_value(c, p, pc);
         case MatchSingleton_kind:
-            return compiler_pattern_constant(c, p, pc);
+            return compiler_pattern_singleton(c, p, pc);
         case MatchSequence_kind:
             return compiler_pattern_sequence(c, p, pc);
         case MatchMapping_kind: