fix(vast_c): C 解析器补齐 match 的 is_switch，并实现 switch / fallthrough

- ParseMatch：Match 由 2 字段改为 3 字段（subject, cases, is_switch=False），修运行期 AttributeError: 'Match' object has no attribute 'is_switch' - 新增 ParseSwitch：switch 脱糖为 is_switch=True 的 Match，支持 case 常量/枚举变体/多值或模式与 default:（标签非法或不支持 if 守卫时 fail-fast） - 新增 ParseFallThrough：fallthrough 脱糖为 c.NoBreak() 标记调用 - 语句分派：match / struct 改为硬关键字，新增 switch / fallthrough 分派
2026-10-02 23:34:33 +08:00
1 parent 74cfaeb917
commit 5de9cb6527
@@ -4329,6 +4329,9 @@ static PyObject *ParseFor(Parser *P, int IsAsync);
 static PyObject *ParseTry(Parser *P);
 static PyObject *ParseWith(Parser *P, int IsAsync);
 static PyObject *ParseMatch(Parser *P);
+static PyObject *ParseSwitch(Parser *P);
+static PyObject *ParseFallThrough(Parser *P);
+static int SwitchPatAllowed(PyObject *Pat);
 static PyObject *ParseFunctionDef(Parser *P, int IsAsync, PyObject *Decorators);
 static PyObject *ParseClassDef(Parser *P, PyObject *Decorators);
 static PyObject *ParseExprList(Parser *P);
@@ -4430,9 +4433,8 @@ static PyObject *ParseStatement(Parser *P) {
        if (TokIsName(T, "class")) {
            return ParseClassDef(P, NULL);
        }
-        /* struct 纯数据类型定义（软关键字：仅"语句起始 + 后随标识符"生效，
-         * 故 `struct = 5` / `x.struct` 作标识符的写法不受影响） */
-        if (TokIsName(T, "struct") && PeekTok(P, 1)->Kind == TK_NAME) {
+        /* struct 纯数据类型定义（硬关键字：语句起始一律按 struct 定义解析） */
+        if (TokIsName(T, "struct")) {
            return ParseStructDef(P, NULL);
        }
        if (TokIsName(T, "if")) {
@@ -4450,18 +4452,18 @@ static PyObject *ParseStatement(Parser *P) {
        if (TokIsName(T, "with")) {
            return ParseWith(P, 0);
        }
+        /* match 多模式匹配（硬关键字：语句起始一律按 match 语句解析） */
        if (TokIsName(T, "match")) {
-            int SaveIdx = P->Idx;
-            PyObject *M = ParseMatch(P);
-            if (M != NULL) {
-                return M;
-            }
-            if (PyErr_Occurred()) {
-                return NULL;
-            }
-            P->Idx = SaveIdx;
-            P->Error = 0;
-            /* 回退为表达式语句 */
+            return ParseMatch(P);
+        }
+        /* switch 多分支（硬关键字，C switch 语义）：desugar 为 is_switch=True 的 Match */
+        if (TokIsName(T, "switch")) {
+            return ParseSwitch(P);
+        }
+        /* fallthrough 关键字（硬）：仅在 switch 的 case 体内合法，脱糖为
+         * `c.NoBreak()` 标记调用，由 switch 生成侧消费 */
+        if (TokIsName(T, "fallthrough")) {
+            return ParseFallThrough(P);
        }
        if (TokIsName(T, "return")) {
            Token *Start = NextTok(P);
@@ -6433,8 +6435,8 @@ static PyObject *ParseMatch(Parser *P) {
        Py_DECREF(Subject);
        return NULL;
    }
-    PyObject *Argv[2] = { Subject, Cases };
-    PyObject *Node = NewNode(P, "Match", Argv, 2);
+    PyObject *Argv[3] = { Subject, Cases, Py_False };
+    PyObject *Node = NewNode(P, "Match", Argv, 3);
    Py_DECREF(Subject);
    Py_DECREF(Cases);
    if (Node != NULL) {
@@ -6443,6 +6445,216 @@ static PyObject *ParseMatch(Parser *P) {
    return Node;
 }

+/* switch 的 case 标签是否合法：只允许常量 / 枚举变体 / 多值或模式
+ * （MatchValue / MatchSingleton / MatchClass / MatchOr<上述>） */
+static int SwitchPatAllowed(PyObject *Pat) {
+    if (Pat == NULL) {
+        return 0;
+    }
+    const char *N = Py_TYPE(Pat)->tp_name;
+    if (strcmp(N, "MatchValue") == 0 || strcmp(N, "MatchSingleton") == 0
+        || strcmp(N, "MatchClass") == 0) {
+        return 1;
+    }
+    if (strcmp(N, "MatchOr") == 0) {
+        PyObject *Pats = PyObject_GetAttrString(Pat, "patterns");
+        if (Pats == NULL) {
+            PyErr_Clear();
+            return 0;
+        }
+        if (!PyList_Check(Pats)) {
+            Py_DECREF(Pats);
+            return 0;
+        }
+        Py_ssize_t Count = PyList_Size(Pats);
+        int Ok = (Count > 0);
+        for (Py_ssize_t I = 0; I < Count && Ok; I++) {
+            if (!SwitchPatAllowed(PyList_GetItem(Pats, I))) {
+                Ok = 0;
+            }
+        }
+        Py_DECREF(Pats);
+        return Ok;
+    }
+    return 0;
+}
+
+/* switch 语句（C switch 语义）：脱糖为 is_switch=True 的 Match
+ *
+ *   switch <expr>:
+ *       case <常量 | 枚举变体>:   # 可 `case 1 | 2:` 多值
+ *       default:
+ *
+ * case 标签只支持常量 / 枚举变体 / 多值或模式，不支持 if 守卫。 */
+static PyObject *ParseSwitch(Parser *P) {
+    Token *Start = NextTok(P); /* switch */
+    PyObject *Subject = ParseExpr(P);
+    if (Subject == NULL) {
+        return NULL;
+    }
+    if (!ExpectOp(P, ":")) {
+        Py_DECREF(Subject);
+        return NULL;
+    }
+    if (!ExpectNEWLINE(P)) {
+        Py_DECREF(Subject);
+        return NULL;
+    }
+    Token *IndentTok = NextTok(P);
+    if (IndentTok->Kind != TK_INDENT) {
+        SyntaxErrorAt(P, IndentTok, "expected INDENT");
+        Py_DECREF(Subject);
+        return NULL;
+    }
+    PyObject *Cases = NewList();
+    if (Cases == NULL) {
+        Py_DECREF(Subject);
+        return NULL;
+    }
+    SkipNEWLINE(P);
+    while (1) {
+        PyObject *Pattern = NULL;
+        Token *CaseStart = NULL;
+        if (AtName(P, "case")) {
+            CaseStart = NextTok(P); /* case */
+            Pattern = ParsePattern(P);
+            if (Pattern == NULL) {
+                Py_DECREF(Cases);
+                Py_DECREF(Subject);
+                return NULL;
+            }
+            if (!SwitchPatAllowed(Pattern)) {
+                SyntaxErrorAt(P, CaseStart,
+                    "switch case label must be a constant or enum variant");
+                Py_DECREF(Pattern);
+                Py_DECREF(Cases);
+                Py_DECREF(Subject);
+                return NULL;
+            }
+            if (AtName(P, "if")) {
+                SyntaxErrorAt(P, PeekTok(P, 0), "switch case does not support if guard");
+                Py_DECREF(Pattern);
+                Py_DECREF(Cases);
+                Py_DECREF(Subject);
+                return NULL;
+            }
+        } else if (AtName(P, "default") && TokIsOp(PeekTok(P, 1), ":")) {
+            CaseStart = NextTok(P); /* default */
+            PyObject *WildArgv[2] = { Py_None, Py_None };
+            Pattern = NewNode(P, "MatchAs", WildArgv, 2);
+            if (Pattern == NULL) {
+                Py_DECREF(Cases);
+                Py_DECREF(Subject);
+                return NULL;
+            }
+            FixLoc(P, Pattern, CaseStart);
+        } else {
+            break;
+        }
+        if (!ExpectOp(P, ":")) {
+            Py_DECREF(Pattern);
+            Py_DECREF(Cases);
+            Py_DECREF(Subject);
+            return NULL;
+        }
+        PyObject *CaseBody = ParseSuite(P);
+        if (CaseBody == NULL) {
+            Py_DECREF(Pattern);
+            Py_DECREF(Cases);
+            Py_DECREF(Subject);
+            return NULL;
+        }
+        PyObject *McArgv[3] = { Pattern, Py_None, CaseBody };
+        PyObject *Mc = NewNode(P, "match_case", McArgv, 3);
+        Py_DECREF(Pattern);
+        Py_DECREF(CaseBody);
+        if (Mc == NULL) {
+            Py_DECREF(Cases);
+            Py_DECREF(Subject);
+            return NULL;
+        }
+        PyList_Append(Cases, Mc);
+        Py_DECREF(Mc);
+        SkipNEWLINE(P);
+    }
+    Token *DedentTok = NextTok(P);
+    if (DedentTok->Kind != TK_DEDENT) {
+        SyntaxErrorAt(P, DedentTok, "expected DEDENT");
+        Py_DECREF(Cases);
+        Py_DECREF(Subject);
+        return NULL;
+    }
+    PyObject *Argv[3] = { Subject, Cases, Py_True };
+    PyObject *Node = NewNode(P, "Match", Argv, 3);
+    Py_DECREF(Subject);
+    Py_DECREF(Cases);
+    if (Node != NULL) {
+        FixLoc(P, Node, Start);
+    }
+    return Node;
+}
+
+/* `fallthrough` 脱糖为 `c.NoBreak()`（switch 生成侧识别的 fallthrough 标记） */
+static PyObject *ParseFallThrough(Parser *P) {
+    Token *Start = NextTok(P); /* fallthrough */
+    PyObject *Load1 = MakeCtx(P, "Load");
+    PyObject *IdC = Load1 ? PyUnicode_FromString("c") : NULL;
+    if (Load1 == NULL || IdC == NULL) {
+        Py_XDECREF(Load1);
+        Py_XDECREF(IdC);
+        return NULL;
+    }
+    PyObject *NameArgv[2] = { IdC, Load1 };
+    PyObject *NameNode = NewNode(P, "Name", NameArgv, 2);
+    Py_DECREF(IdC);
+    Py_DECREF(Load1);
+    if (NameNode == NULL) {
+        return NULL;
+    }
+    FixLoc(P, NameNode, Start);
+    PyObject *Load2 = MakeCtx(P, "Load");
+    PyObject *AttrStr = Load2 ? PyUnicode_FromString("NoBreak") : NULL;
+    if (Load2 == NULL || AttrStr == NULL) {
+        Py_XDECREF(Load2);
+        Py_XDECREF(AttrStr);
+        Py_DECREF(NameNode);
+        return NULL;
+    }
+    PyObject *AttrArgv[3] = { NameNode, AttrStr, Load2 };
+    PyObject *AttrNode = NewNode(P, "Attribute", AttrArgv, 3);
+    Py_DECREF(AttrStr);
+    Py_DECREF(Load2);
+    Py_DECREF(NameNode);
+    if (AttrNode == NULL) {
+        return NULL;
+    }
+    FixLoc(P, AttrNode, Start);
+    PyObject *Args = NewList();
+    PyObject *Keywords = NewList();
+    if (Args == NULL || Keywords == NULL) {
+        Py_XDECREF(Args);
+        Py_XDECREF(Keywords);
+        Py_DECREF(AttrNode);
+        return NULL;
+    }
+    PyObject *CallArgv[3] = { AttrNode, Args, Keywords };
+    PyObject *CallNode = NewNode(P, "Call", CallArgv, 3);
+    Py_DECREF(Args);
+    Py_DECREF(Keywords);
+    Py_DECREF(AttrNode);
+    if (CallNode == NULL) {
+        return NULL;
+    }
+    FixLoc(P, CallNode, Start);
+    PyObject *ExprArgv[1] = { CallNode };
+    PyObject *ExprNode = NewNode(P, "Expr", ExprArgv, 1);
+    Py_DECREF(CallNode);
+    if (ExprNode != NULL) {
+        FixLoc(P, ExprNode, Start);
+    }
+    return ExprNode;
+}
+
 /* 模式（顶层，处理 | 或模式） */
 static PyObject *ParsePattern(Parser *P) {
    Token *Start = PeekTok(P, 0);