fix(match): merge 可达性用局部标志记录，消除 case 体内嵌套 if 污染

主 match/sequence/simple 三条路径：case 体内嵌套 If（无 else + return）翻译时把 _ctrl_merge_reachable 置 1，全 case return 的 match 被误判 merge 可达 → 函数收尾 fail-fast '流程掉出末尾'（LLvmLiteTest includes/llvmlite/__module.vp _is_opaque_struct）。改用局部变量记录本 match 自身的 br end_bb，收尾覆盖全局标志

App/lib/core/Handles/HandlesMatch.vp

@@ -80,8 +80,14 @@ class MatchHandle(HandlesBase.Mixin):
         if builder is None or func is None:
             return 0
 
-        # 追加90：match merge 可达性重置（下方 br end_bb 处置 1）
+        # 追加90：match merge 可达性重置（下方 br end_bb 处置 1）。
+        # 嵌套语句（case 体内的 If/While 等）翻译时会改写 _ctrl_merge_reachable，
+        # 用局部变量单独记录"本 match 是否有 br 进入 end_bb"，收尾时覆盖，
+        # 消除嵌套控制流污染（_is_opaque_struct 的 case 内 if 无 else + return
+        # 把标志置 1，全 case return 的 match 被误判 merge 可达 → 函数收尾
+        # fail-fast "流程掉出末尾"，见 LLvmLiteTest/__module.vp）。
         trans._ctrl_merge_reachable = 0
+        m_merge_reach: int = 0
 
         m_node: ast.Match | t.CPtr = (ast.Match | t.CPtr)(node)
 
@@ -513,6 +519,7 @@ class MatchHandle(HandlesBase.Mixin):
                     and nb == 0:
                 llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                m_merge_reach = 1
 
             i = i + 1
 
@@ -523,6 +530,7 @@ class MatchHandle(HandlesBase.Mixin):
             if llvmlite.builder_cur_block_is_terminated(builder) == 0:
                 llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                m_merge_reach = 1
         else:
             # 有显式 default：翻译 default case body（找到 is_def==1 的 case）
             di: int = 0
@@ -548,9 +556,13 @@ class MatchHandle(HandlesBase.Mixin):
             if llvmlite.builder_cur_block_is_terminated(builder) == 0:
                 llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                m_merge_reach = 1
 
         # 9. 定位到 end 块
         llvmlite.position_at_end(builder, end_bb)
+        # 用本 match 自身的 br 记录覆盖，消除 case 体内嵌套控制流对
+        # _ctrl_merge_reachable 的污染（全 case return 时应为不可达）
+        trans._ctrl_merge_reachable = m_merge_reach
         return 0
 
     # ============================================================
@@ -721,6 +733,9 @@ class MatchHandle(HandlesBase.Mixin):
         func: llvmlite.Function | t.CPtr = trans._cur_func
         if builder is None or func is None:
             return 0
+        # 同主路径：局部记录本 sequence match 的 br end_bb，收尾覆盖
+        # _ctrl_merge_reachable，消除 case 体内嵌套控制流污染
+        sq_merge_reach: int = 0
 
         # 1. 求值 subject 各元素
         elts: list[ast.AST | t.CPtr] | t.CPtr = None
@@ -987,6 +1002,7 @@ class MatchHandle(HandlesBase.Mixin):
                     else:
                         llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                sq_merge_reach = 1
             ci = ci + 1
 
         # 7. default 块
@@ -1014,9 +1030,12 @@ class MatchHandle(HandlesBase.Mixin):
                 di = di + 1
         if llvmlite.builder_cur_block_is_terminated(builder) == 0:
             llvmlite.build_br(builder, end_bb)
+            sq_merge_reach = 1
 
         # 8. 定位到 end
         llvmlite.position_at_end(builder, end_bb)
+        # 覆盖嵌套控制流污染（同主路径）
+        trans._ctrl_merge_reachable = sq_merge_reach
         return 0
 
     # ============================================================
@@ -1030,6 +1049,9 @@ class MatchHandle(HandlesBase.Mixin):
         pool: memhub.MemBuddy | t.CPtr = trans.Pool
         builder: llvmlite.IRBuilder | t.CPtr = trans._cur_builder
         func: llvmlite.Function | t.CPtr = trans._cur_func
+        # 同主路径：局部记录本 simple match 的 br end_bb，收尾覆盖
+        # _ctrl_merge_reachable，消除 case 体内嵌套控制流污染
+        sm_merge_reach: int = 0
 
         # 1. subject 转 i32（若已 i32 直接用，否则 ptrtoint）
         i32_ty: llvmlite.LLVMType | t.CPtr = llvmlite.Int32(pool)
@@ -1205,6 +1227,7 @@ class MatchHandle(HandlesBase.Mixin):
                     and nb == 0:
                 llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                sm_merge_reach = 1
 
             i = i + 1
 
@@ -1214,6 +1237,7 @@ class MatchHandle(HandlesBase.Mixin):
             if llvmlite.builder_cur_block_is_terminated(builder) == 0:
                 llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                sm_merge_reach = 1
         else:
             di: int = 0
             while di < collected:
@@ -1238,9 +1262,12 @@ class MatchHandle(HandlesBase.Mixin):
             if llvmlite.builder_cur_block_is_terminated(builder) == 0:
                 llvmlite.build_br(builder, end_bb)
                 trans._ctrl_merge_reachable = 1
+                sm_merge_reach = 1
 
         # 8. 定位到 end
         llvmlite.position_at_end(builder, end_bb)
+        # 覆盖嵌套控制流污染（同主路径）
+        trans._ctrl_merge_reachable = sm_merge_reach
         return 0