feat: multi-stmt match arms and block-as-expression

Blocks can yield a value: last expression statement is the result.
Match arms accept block bodies, so multi-statement arms work:

  match n {
    1 => { let a = 10; a + 1 },
    _ => 0
  }

Bootstrap: lowerBlock(asExpr) lifts the trailing skExpr. Selfhost: parse
{...} as ekBlock, emit __blk_N yield temps (retTypeKind -2), and treat
only non-empty strValue as match/block yield. Nested enum/struct pattern
bindings recurse in both compilers.

Example: match_block.bux. Selfhost-loop remains binary-identical.

Makefile

@@ -3,7 +3,7 @@ SRC := bootstrap/main.nim
 OUT := buxc
 BUILD_DIR := build
 
-EXAMPLES := hello fibonacci factorial structs enums methods algebraic_enums generics generics_struct generic_infer generic_infer2 extend_generic pattern_matching strings strings2 map result_option try_operator ownership ctfe async concurrency os_time process json iter trait_bounds channel sync jwt stdlib_ergonomics tuples func_ptr map_remove array_iter_extra string_extra multi_closure iter_hof closure_control match_let string_interp iter_generic struct_tuple_pat
+EXAMPLES := hello fibonacci factorial structs enums methods algebraic_enums generics generics_struct generic_infer generic_infer2 extend_generic pattern_matching strings strings2 map result_option try_operator ownership ctfe async concurrency os_time process json iter trait_bounds channel sync jwt stdlib_ergonomics tuples func_ptr map_remove array_iter_extra string_extra multi_closure iter_hof closure_control match_let string_interp iter_generic struct_tuple_pat match_block
 
 .PHONY: all build dev debug test clean clean-all test-examples selfhost test-golden test-errors selfhost-loop lsp
 

bootstrap/hir_lower.nim

@@ -185,19 +185,23 @@ proc matchPatternBindings(ctx: var LowerCtx, subject: HirNode, pattern: Pattern,
                                typ: makePointer(variantStructTy), loc: loc)
       payloadBase = HirNode(kind: hLoad, loadPtr: variantPtr, typ: variantStructTy, loc: loc)
     for i, arg in pattern.patEnumArgs:
-      if arg == nil or arg.kind != pkIdent:
+      if arg == nil:
         continue
       let fieldName = variantName & "_" & $i
       let fieldTy = if i < fieldTypes.len: fieldTypes[i] else: makeInt()
       let fieldPtr = HirNode(kind: hFieldPtr, fieldPtrBase: payloadBase, fieldName: fieldName,
                              typ: makePointer(fieldTy), loc: loc)
       let fieldLoad = HirNode(kind: hLoad, loadPtr: fieldPtr, typ: fieldTy, loc: loc)
-      if arg.patIdent notin ctx.patternBoundNames:
-        result.add(hirAlloca(arg.patIdent, fieldTy, loc))
-        ctx.patternBoundNames.incl(arg.patIdent)
-      result.add(hirStore(hirVar(arg.patIdent, fieldTy, loc), fieldLoad, loc))
+      if arg.kind == pkIdent:
+        if arg.patIdent notin ctx.patternBoundNames:
+          result.add(hirAlloca(arg.patIdent, fieldTy, loc))
+          ctx.patternBoundNames.incl(arg.patIdent)
+        result.add(hirStore(hirVar(arg.patIdent, fieldTy, loc), fieldLoad, loc))
+      else:
+        # Nested: Option::Some((a, b)), Pair::Two(Point { x, y })
+        result.add(ctx.matchPatternBindings(fieldLoad, arg, subjectEnumName, subjectHasData, loc))
     for nf in pattern.patEnumNamed:
-      if nf.pattern == nil or nf.pattern.kind != pkIdent:
+      if nf.pattern == nil:
         continue
       var fieldTy = makeInt()
       for entry in namedFields:
@@ -211,10 +215,13 @@ proc matchPatternBindings(ctx: var LowerCtx, subject: HirNode, pattern: Pattern,
       let fieldPtr = HirNode(kind: hFieldPtr, fieldPtrBase: variantLoad, fieldName: nf.name,
                              typ: makePointer(fieldTy), loc: loc)
       let fieldLoad = HirNode(kind: hLoad, loadPtr: fieldPtr, typ: fieldTy, loc: loc)
-      if nf.pattern.patIdent notin ctx.patternBoundNames:
-        result.add(hirAlloca(nf.pattern.patIdent, fieldTy, loc))
-        ctx.patternBoundNames.incl(nf.pattern.patIdent)
-      result.add(hirStore(hirVar(nf.pattern.patIdent, fieldTy, loc), fieldLoad, loc))
+      if nf.pattern.kind == pkIdent:
+        if nf.pattern.patIdent notin ctx.patternBoundNames:
+          result.add(hirAlloca(nf.pattern.patIdent, fieldTy, loc))
+          ctx.patternBoundNames.incl(nf.pattern.patIdent)
+        result.add(hirStore(hirVar(nf.pattern.patIdent, fieldTy, loc), fieldLoad, loc))
+      else:
+        result.add(ctx.matchPatternBindings(fieldLoad, nf.pattern, subjectEnumName, subjectHasData, loc))
   of pkGuarded:
     result.add(ctx.matchPatternBindings(subject, pattern.patGuardedInner, subjectEnumName, subjectHasData, loc))
   of pkTuple:
@@ -536,7 +543,7 @@ proc resolveTypeExpr(ctx: var LowerCtx, te: TypeExpr): Type =
 # Forward declarations
 proc lowerExpr(ctx: var LowerCtx, expr: Expr): HirNode
 proc lowerStmt(ctx: var LowerCtx, stmt: Stmt): HirNode
-proc lowerBlock(ctx: var LowerCtx, blk: Block): HirNode
+proc lowerBlock(ctx: var LowerCtx, blk: Block, asExpr = false): HirNode
 proc lowerClosureFunc(ctx: var LowerCtx, expr: Expr): HirFunc
 
 proc resolveExprType(ctx: var LowerCtx, expr: Expr): Type =
@@ -1339,7 +1346,7 @@ proc lowerExpr(ctx: var LowerCtx, expr: Expr): HirNode =
                    typ: typ, loc: loc)
 
   of ekBlock:
-    return ctx.lowerBlock(expr.exprBlock)
+    return ctx.lowerBlock(expr.exprBlock, asExpr = true)
 
   of ekPostfix:
     let operand = ctx.lowerExpr(expr.exprPostfixOperand)
@@ -1926,26 +1933,37 @@ proc lowerStmt(ctx: var LowerCtx, stmt: Stmt): HirNode =
     return HirNode(kind: hLit, litToken: Token(kind: tkIntLiteral, text: "0", loc: loc),
                    typ: makeVoid(), loc: loc)
 
-proc lowerBlock(ctx: var LowerCtx, blk: Block): HirNode =
+proc lowerBlock(ctx: var LowerCtx, blk: Block, asExpr = false): HirNode =
+  ## asExpr=true: block is used as a value (`let x = { ... }`, match arm body).
+  ## Last skExpr becomes the block result. Statement blocks (func body, if/while)
+  ## keep asExpr=false so trailing void calls stay as statements.
   if blk == nil: return nil
   var stmts: seq[HirNode] = @[]
   for s in blk.stmts:
     let hir = ctx.lowerStmt(s)
     if hir != nil:
       stmts.add(hir)
-  # If the last statement is an expression, make it the block's result expression
   var expr: HirNode = nil
-  if stmts.len > 0 and stmts[^1].kind == hBlock and stmts[^1].blockExpr != nil:
-    # Nested block expression (e.g., from match lowering) — lift it
+  if asExpr and stmts.len > 0 and blk.stmts.len > 0 and blk.stmts[^1].kind == skExpr:
+    let last = stmts[^1]
+    if last.kind == hBlock and last.blockExpr != nil:
+      # Nested yield block (match, block-expr) — lift result, keep side-effect stmts
+      stmts[^1] = hirBlock(last.blockStmts, nil, makeVoid(), last.loc)
+      expr = last.blockExpr
+    elif last.kind in {hIf, hWhile, hLoop, hReturn, hBreak, hContinue, hAlloca, hStore, hAssign}:
+      discard
+    else:
+      # hBinary, hCall, hLit, hVar, hLoad, … — value expression
+      expr = last
+      discard stmts.pop()
+  elif stmts.len > 0 and stmts[^1].kind == hBlock and stmts[^1].blockExpr != nil:
+    # Nested block expression (e.g., match) inside statement context — lift for
+    # function last-expr return via blockExpr when present
     let last = stmts[^1]
     stmts[^1] = hirBlock(last.blockStmts, nil, makeVoid(), last.loc)
     expr = last.blockExpr
-  elif stmts.len > 0 and stmts[^1].kind != hBlock:
-    # Last stmt is a simple expression-like node — we can't easily extract it,
-    # but for hVar/hLit/hCall etc. we could treat them as block expr.
-    # For now, leave as-is to avoid breaking control-flow statements.
-    discard
-  return hirBlock(stmts, expr, if expr != nil: expr.typ else: makeVoid(), blk.loc, isScope = true)
+  let typ = if expr != nil and expr.typ != nil: expr.typ else: makeVoid()
+  return hirBlock(stmts, expr, typ, blk.loc, isScope = true)
 
 proc lowerFunc*(ctx: var LowerCtx, decl: Decl): HirFunc =
   # Set up type substitution for generic functions

docs/LanguageRef.md

@@ -396,6 +396,21 @@ match p {
     Point { x, y } => x * 10 + y,
     _ => -1
 }
+
+// Multi-statement arm bodies (block expression; last expr is the value)
+match n {
+    1 => {
+        let a: int = 10;
+        a + 1
+    },
+    _ => 0
+}
+
+// Block as expression
+let r: int = {
+    let x: int = 5;
+    x + 6
+};
 ```
 
 ---

docs/QUALITY_PLAN.md

@@ -273,9 +273,21 @@ A (stdlib ergonomics)  →  B (compiler holes)  →  C (ownership depth)
 
 ---
 
+## Сесия 16 (match block arms + block expressions)
+
+1. **Block-as-expression:** `let r = { let x = 1; x + 2 }` — last skExpr is the value
+2. **Multi-stmt match arms:** `1 => { PrintLine("…"); let a = 10; a + 1 }`
+3. Bootstrap: `lowerBlock(..., asExpr)` promotes last expression; nested enum/struct pattern bindings
+4. Selfhost: parse `{ … }` as `ekBlock`; yield temps `__blk_N`; fix `IsMatchYield` null-strValue false positive; retTypeKind `-2` for expr blocks
+5. Nested: `Shape::Dot(Point { x, y })` works on bootstrap; selfhost covers struct/tuple/enum + block arms
+6. Example: `examples/match_block.bux`
+7. Verified: bootstrap + **buxc2** + selfhost-loop IDENTICAL ✓
+
+---
+
 ## Следващи стъпки
 
-1. Match arm multi-stmt bodies (beyond single expr)
-2. Nested patterns deeper (`Some((a, b))`, `Point { x: (a, b) }`)
-3. LSP: wire hover types from real sema
-4. Generic type inference for `Iter_Map` without explicit `<T,U>`
+1. Deeper nested patterns (`Some((a, b))` with multi-field enum layout ergonomics)
+2. LSP: wire hover types from real sema
+3. Generic type inference for `Iter_Map` without explicit `<T,U>`
+4. Match arm guards (`p if cond => …`)

examples/match_block.bux

@@ -0,0 +1,81 @@
+// Multi-stmt match arms (block bodies) + block-as-expression
+import Std::Io::{PrintLine, PrintInt};
+import Std::Test::{Test_AssertEqInt, Test_Pass};
+
+struct Point {
+    x: int,
+    y: int,
+}
+
+enum Option {
+    Some(int),
+    None
+}
+
+func Classify(n: int) -> int {
+    match n {
+        1 => {
+            let a: int = 10;
+            a + 1
+        },
+        2 => {
+            PrintLine("two");
+            let b: int = 20;
+            b * 2
+        },
+        _ => 0
+    }
+}
+
+func Main() -> int {
+    Test_AssertEqInt(Classify(1), 11);
+    Test_AssertEqInt(Classify(2), 40);
+    Test_AssertEqInt(Classify(9), 0);
+
+    // Block as expression outside match
+    let r: int = {
+        let x: int = 5;
+        let y: int = 6;
+        x + y
+    };
+    Test_AssertEqInt(r, 11);
+
+    // Tuple pattern + block body
+    let t: (int, int) = (3, 4);
+    let u: int = match t {
+        (a, b) => {
+            let prod: int = a * b;
+            prod
+        },
+        _ => 0
+    };
+    Test_AssertEqInt(u, 12);
+
+    // Struct pattern + block body
+    let p: Point = Point { x: 2, y: 5 };
+    let z: int = match p {
+        Point { x: px, y: py } => {
+            let sum: int = px + py;
+            sum
+        },
+        _ => -1
+    };
+    Test_AssertEqInt(z, 7);
+
+    // Enum payload + block
+    let opt: Option = Option { tag: Option_Some };
+    opt.data.Some_0 = 7;
+    let v: int = match opt {
+        Option::Some(n) => {
+            let doubled: int = n + n;
+            doubled
+        },
+        Option::None => 0
+    };
+    Test_AssertEqInt(v, 14);
+
+    PrintInt(Classify(2));
+    PrintLine("");
+    Test_Pass("match_block");
+    return 0;
+}

src/hir_lower.bux

@@ -805,25 +805,25 @@ func Lcx_PatternBindings(ctx: *LowerCtx, subject: *HirNode, pat: *Pattern,
     var arg: *Pattern = pat.patArgs;
     var ai: int = 0;
     while arg != null as *Pattern {
-        if arg.kind == pkIdent {
-            var ftype: String = "int";
-            if ai == 0 { ftype = fieldType0; }
-            else if ai == 1 { ftype = fieldType1; }
-            let fieldName: String = String_Concat(String_Concat(variantName, "_"), String_FromInt(ai as int64));
+        var ftype: String = "int";
+        if ai == 0 { ftype = fieldType0; }
+        else if ai == 1 { ftype = fieldType1; }
+        let fieldName: String = String_Concat(String_Concat(variantName, "_"), String_FromInt(ai as int64));
 
-            let fPtr: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
-            fPtr.kind = hFieldPtr;
-            fPtr.line = line;
-            fPtr.column = col;
-            fPtr.strValue = fieldName;
-            fPtr.child1 = payloadBase;
-            let fLoad: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
-            fLoad.kind = hLoad;
-            fLoad.line = line;
-            fLoad.column = col;
-            fLoad.child1 = fPtr;
-            fLoad.typeName = ftype;
+        let fPtr: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
+        fPtr.kind = hFieldPtr;
+        fPtr.line = line;
+        fPtr.column = col;
+        fPtr.strValue = fieldName;
+        fPtr.child1 = payloadBase;
+        let fLoad: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
+        fLoad.kind = hLoad;
+        fLoad.line = line;
+        fLoad.column = col;
+        fLoad.child1 = fPtr;
+        fLoad.typeName = ftype;
 
+        if arg.kind == pkIdent && !String_Eq(arg.patIdent, "_") {
             let alloca: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
             alloca.kind = hAlloca;
             alloca.line = line;
@@ -842,7 +842,6 @@ func Lcx_PatternBindings(ctx: *LowerCtx, subject: *HirNode, pat: *Pattern,
             store.child2 = fLoad;
             alloca.child3 = store;
 
-            // Define in scope so body idents resolve
             var bsym: Symbol;
             bsym.kind = skVar;
             bsym.name = arg.patIdent;
@@ -861,6 +860,19 @@ func Lcx_PatternBindings(ctx: *LowerCtx, subject: *HirNode, pat: *Pattern,
                 tail.child3 = alloca;
                 tail = store;
             }
+        } else if arg.kind == pkTuple || arg.kind == pkStruct || arg.kind == pkEnum {
+            // Nested pattern on payload field
+            let nested: *HirNode = Lcx_PatternBindings(ctx, fLoad, arg, subjectEnumName, subjectHasData, line, col);
+            if nested != null as *HirNode {
+                if head == null as *HirNode {
+                    head = nested;
+                    tail = nested;
+                    while tail.child3 != null as *HirNode { tail = tail.child3; }
+                } else {
+                    tail.child3 = nested;
+                    while tail.child3 != null as *HirNode { tail = tail.child3; }
+                }
+            }
         }
         arg = arg.patNext;
         ai = ai + 1;
@@ -872,6 +884,8 @@ func Lcx_PatternBindings(ctx: *LowerCtx, subject: *HirNode, pat: *Pattern,
 func Lcx_IsMatchYield(n: *HirNode) -> bool {
     if n == null as *HirNode { return false; }
     if n.kind != hBlock { return false; }
+    // strValue must be a real temp name — null/"" is a plain statement block
+    if n.strValue == null as String { return false; }
     return !String_Eq(n.strValue, "");
 }
 
@@ -957,7 +971,7 @@ func Lcx_LowerMatch(ctx: *LowerCtx, expr: *Expr) -> *HirNode {
         // Pattern bindings before body (so body idents resolve)
         let bindHead: *HirNode = Lcx_PatternBindings(ctx, subject, cur.pattern, subjectEnumName, subjectHasData, line, col);
         let bodyHir: *HirNode = Lcx_LowerExpr(ctx, cur.body);
-        // result = body
+        // result = body (expand block/match yield: run stmts then store result var)
         let storeNode: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
         storeNode.kind = hStore;
         storeNode.line = line;
@@ -966,20 +980,32 @@ func Lcx_LowerMatch(ctx: *LowerCtx, expr: *Expr) -> *HirNode {
         resVar.kind = hVar;
         resVar.strValue = resultName;
         storeNode.child1 = resVar;
-        storeNode.child2 = bodyHir;
+        var bodyPrefix: *HirNode = null as *HirNode;
+        if Lcx_IsMatchYield(bodyHir) {
+            storeNode.child2 = Lcx_YieldVarOf(bodyHir);
+            bodyHir.strValue = "";
+            bodyPrefix = bodyHir.child1;
+        } else {
+            storeNode.child2 = bodyHir;
+        }
 
-        // armBlock = bindings... → storeNode
+        // armBlock = bindings → body stmts → store
         let armBlock: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
         armBlock.kind = hBlock;
         armBlock.line = line;
         armBlock.column = col;
-        if bindHead != null as *HirNode {
-            armBlock.child1 = bindHead;
-            // find tail of bind chain
-            var bt: *HirNode = bindHead;
-            while bt.child3 != null as *HirNode {
-                bt = bt.child3;
-            }
+        var chainHead: *HirNode = bindHead;
+        if chainHead == null as *HirNode {
+            chainHead = bodyPrefix;
+        } else if bodyPrefix != null as *HirNode {
+            var bt0: *HirNode = chainHead;
+            while bt0.child3 != null as *HirNode { bt0 = bt0.child3; }
+            bt0.child3 = bodyPrefix;
+        }
+        if chainHead != null as *HirNode {
+            armBlock.child1 = chainHead;
+            var bt: *HirNode = chainHead;
+            while bt.child3 != null as *HirNode { bt = bt.child3; }
             bt.child3 = storeNode;
         } else {
             armBlock.child1 = storeNode;
@@ -2158,6 +2184,7 @@ func Lcx_LowerExpr(ctx: *LowerCtx, expr: *Expr) -> *HirNode {
     }
 
     // Block expression (boolValue = true means unsafe block)
+    // retTypeKind -2 → yield last expression as block value
     if kind == ekBlock {
         if expr.refBlock != null as *Block {
             if expr.boolValue {
@@ -2165,12 +2192,12 @@ func Lcx_LowerExpr(ctx: *LowerCtx, expr: *Expr) -> *HirNode {
                 let oldRelease: bool = ctx.releaseFunc;
                 ctx.checkedFunc = false;
                 ctx.releaseFunc = false;
-                let blockNode: *HirNode = Lcx_LowerBlock(ctx, expr.refBlock, -1);
+                let blockNode: *HirNode = Lcx_LowerBlock(ctx, expr.refBlock, -2);
                 ctx.checkedFunc = oldChecked;
                 ctx.releaseFunc = oldRelease;
                 return blockNode;
             } else {
-                return Lcx_LowerBlock(ctx, expr.refBlock, -1);
+                return Lcx_LowerBlock(ctx, expr.refBlock, -2);
             }
         }
         return n;
@@ -3053,27 +3080,30 @@ func Lcx_LowerBlock(ctx: *LowerCtx, block: *Block, retTypeKind: int) -> *HirNode
     if block == null as *Block { return null as *HirNode; }
     if block.stmtCount == 0 { return null as *HirNode; }
 
-    // Build a linked list of HirNodes via child3:
-    //   node1 (stmt1) → child3 → node2 (stmt2) → child3 → node3 (stmt3) → null
-    // child3 is safe for chaining because:
-    //   hStore: child1=alloca, child2=value, child3 unused
-    //   hReturn: child1=value, child2/child3 unused
-    //   hCall: child1=arg1, child2=arg2, child3 unused
+    // retTypeKind:
+    //   >= 0  → function body; last skExpr becomes return
+    //   -1    → statement block (if/while/for); no return, no yield
+    //   -2    → block-as-expression (match arm / let { ... }); yield last skExpr
+    let asExpr: bool = retTypeKind == -2;
+    var yieldName: String = "";
+    if asExpr {
+        ctx.varCounter = ctx.varCounter + 1;
+        yieldName = String_Concat("__blk_", String_FromInt(ctx.varCounter as int64));
+    }
+
+    // Build a linked list of HirNodes via child3
     var firstNode: *HirNode = null as *HirNode;
     var prevNode: *HirNode = null as *HirNode;
     var stmt: *Stmt = block.firstStmt;
-    var lastStmt: *Stmt = null as *Stmt;
     while stmt != null as *Stmt {
-        lastStmt = stmt;
         let isLast: bool = stmt.nextStmt == null as *Stmt;
-        // Last expression statement in a non-void function → implicit return
-        // (supports `func F() -> T { match ... }` / bare value as body)
         var lowered: *HirNode = null as *HirNode;
-        if isLast && retTypeKind != tyVoid && retTypeKind != tyUnknown && retTypeKind >= 0
+
+        // Last expression statement in a non-void function → implicit return
+        if isLast && !asExpr && retTypeKind != tyVoid && retTypeKind != tyUnknown && retTypeKind >= 0
             && stmt.kind == skExpr && stmt.child1 != null as *Expr {
             let exprNode: *HirNode = Lcx_LowerExpr(ctx, stmt.child1);
             if exprNode != null as *HirNode {
-                // Match (and similar multi-stmt yields): hBlock with strValue = result var
                 if exprNode.kind == hBlock && !String_Eq(exprNode.strValue, "") {
                     let retVar: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
                     retVar.kind = hVar;
@@ -3083,7 +3113,6 @@ func Lcx_LowerBlock(ctx: *LowerCtx, block: *Block, retTypeKind: int) -> *HirNode
                     retNode.line = stmt.line;
                     retNode.column = stmt.column;
                     retNode.child1 = retVar;
-                    // Append return at end of match block's child3 chain
                     var lastInBlock: *HirNode = exprNode.child1;
                     if lastInBlock == null as *HirNode {
                         exprNode.child1 = retNode;
@@ -3093,7 +3122,6 @@ func Lcx_LowerBlock(ctx: *LowerCtx, block: *Block, retTypeKind: int) -> *HirNode
                         }
                         lastInBlock.child3 = retNode;
                     }
-                    // Clear yield marker so emit treats it as plain block
                     exprNode.strValue = "";
                     lowered = exprNode;
                 } else if exprNode.kind == hReturn {
@@ -3107,6 +3135,53 @@ func Lcx_LowerBlock(ctx: *LowerCtx, block: *Block, retTypeKind: int) -> *HirNode
                     lowered = retNode;
                 }
             }
+        } else if isLast && asExpr && stmt.kind == skExpr && stmt.child1 != null as *Expr {
+            // Block-as-expression: last expr is the yield value
+            let exprNode: *HirNode = Lcx_LowerExpr(ctx, stmt.child1);
+            // alloca yield temp
+            let allocaN: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
+            allocaN.kind = hAlloca;
+            allocaN.line = stmt.line;
+            allocaN.column = stmt.column;
+            allocaN.strValue = yieldName;
+            allocaN.typeName = "int";
+            if exprNode != null as *HirNode && exprNode.typeName != null as String
+                && !String_Eq(exprNode.typeName, "") {
+                allocaN.typeName = exprNode.typeName;
+            }
+            // store: yield = value (handle nested match yield)
+            let storeN: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
+            storeN.kind = hStore;
+            storeN.line = stmt.line;
+            storeN.column = stmt.column;
+            let yv: *HirNode = bux_alloc(sizeof(HirNode)) as *HirNode;
+            yv.kind = hVar;
+            yv.strValue = yieldName;
+            storeN.child1 = yv;
+            if exprNode != null as *HirNode && Lcx_IsMatchYield(exprNode) {
+                // Expand nested match stmts then store its result var
+                let yvar: *HirNode = Lcx_YieldVarOf(exprNode);
+                storeN.child2 = yvar;
+                exprNode.strValue = "";
+                // chain: exprNode stmts → alloca → store
+                var lastIn: *HirNode = exprNode.child1;
+                if lastIn == null as *HirNode {
+                    exprNode.child1 = allocaN;
+                    allocaN.child3 = storeN;
+                    lowered = exprNode;
+                } else {
+                    while lastIn.child3 != null as *HirNode {
+                        lastIn = lastIn.child3;
+                    }
+                    lastIn.child3 = allocaN;
+                    allocaN.child3 = storeN;
+                    lowered = exprNode;
+                }
+            } else {
+                storeN.child2 = exprNode;
+                allocaN.child3 = storeN;
+                lowered = allocaN;
+            }
         } else {
             lowered = Lcx_LowerStmt(ctx, stmt);
         }
@@ -3115,8 +3190,12 @@ func Lcx_LowerBlock(ctx: *LowerCtx, block: *Block, retTypeKind: int) -> *HirNode
                 firstNode = lowered;
                 prevNode = lowered;
             } else {
+                // Walk to end of chain (lowered may itself be a multi-node chain)
                 prevNode.child3 = lowered;
                 prevNode = lowered;
+                while prevNode.child3 != null as *HirNode {
+                    prevNode = prevNode.child3;
+                }
             }
         }
         stmt = stmt.nextStmt;
@@ -3129,6 +3208,10 @@ func Lcx_LowerBlock(ctx: *LowerCtx, block: *Block, retTypeKind: int) -> *HirNode
     n.column = block.column;
     n.boolValue = true;
     n.child1 = firstNode;
+    if asExpr && !String_Eq(yieldName, "") {
+        n.strValue = yieldName;
+        n.typeName = "int";
+    }
     return n;
 }
 

src/parser.bux

@@ -661,6 +661,14 @@ func parserParsePrimary(p: *Parser) -> *Expr {
         return parserParseClosure(p);
     }
 
+    // Block expression { stmts; value }
+    if kind == tkLBrace {
+        let e: *Expr = parserMakeExpr(ekBlock, line, col);
+        e.boolValue = false;
+        e.refBlock = parserParseBlock(p);
+        return e;
+    }
+
     // unsafe { ... } — unsafe block expression
     if kind == tkUnsafe {
         discard parserAdvance(p);

src/sema.bux

@@ -446,10 +446,10 @@ func Sema_BindPattern(sema: *Sema, pat: *Pattern, subject: *Expr) {
         var arg: *Pattern = pat.patArgs;
         var ai: int = 0;
         while arg != null as *Pattern {
+            var ftype: String = "int";
+            if ai == 0 { ftype = fieldType0; }
+            else if ai == 1 { ftype = fieldType1; }
             if arg.kind == pkIdent {
-                var ftype: String = "int";
-                if ai == 0 { ftype = fieldType0; }
-                else if ai == 1 { ftype = fieldType1; }
                 var bsym: Symbol;
                 Sema_ZeroInitSymbol(&bsym);
                 bsym.kind = skVar;
@@ -467,6 +467,14 @@ func Sema_BindPattern(sema: *Sema, pat: *Pattern, subject: *Expr) {
                 bsym.isPublic = false;
                 bsym.decl = null as *Decl;
                 discard Scope_Define(sema.scope, bsym);
+            } else {
+                // Nested pattern: synthesize a fake subject expr with payload type
+                let fake: *Expr = bux_alloc(sizeof(Expr)) as *Expr;
+                let fte: *TypeExpr = bux_alloc(sizeof(TypeExpr)) as *TypeExpr;
+                fte.kind = tekNamed;
+                fte.typeName = ftype;
+                fake.refType = fte;
+                Sema_BindPattern(sema, arg, fake);
             }
             arg = arg.patNext;
             ai = ai + 1;
@@ -478,19 +486,17 @@ func Sema_BindPattern(sema: *Sema, pat: *Pattern, subject: *Expr) {
         var ei: int = 0;
         var elem: *Pattern = pat.patArgs;
         while elem != null as *Pattern {
-            if elem.kind == pkIdent {
-                var ety: String = "int";
-                // Tuple_int_int → fields are ints by default; prefer subject type args if present
-                if subject != null as *Expr && subject.refType != null as *TypeExpr {
-                    if subject.refType.kind == tekTuple {
-                        // typeArgName0 / typeArgName1 store element type names when available
-                        if ei == 0 && !String_Eq(subject.refType.typeArgName0, "") {
-                            ety = subject.refType.typeArgName0;
-                        } else if ei == 1 && !String_Eq(subject.refType.typeArgName1, "") {
-                            ety = subject.refType.typeArgName1;
-                        }
+            var ety: String = "int";
+            if subject != null as *Expr && subject.refType != null as *TypeExpr {
+                if subject.refType.kind == tekTuple {
+                    if ei == 0 && !String_Eq(subject.refType.typeArgName0, "") {
+                        ety = subject.refType.typeArgName0;
+                    } else if ei == 1 && !String_Eq(subject.refType.typeArgName1, "") {
+                        ety = subject.refType.typeArgName1;
                     }
                 }
+            }
+            if elem.kind == pkIdent {
                 var bsym: Symbol;
                 Sema_ZeroInitSymbol(&bsym);
                 bsym.kind = skVar;
@@ -505,6 +511,13 @@ func Sema_BindPattern(sema: *Sema, pat: *Pattern, subject: *Expr) {
                 bsym.refType = te;
                 bsym.isMutable = false;
                 discard Scope_Define(sema.scope, bsym);
+            } else {
+                let fake: *Expr = bux_alloc(sizeof(Expr)) as *Expr;
+                let fte: *TypeExpr = bux_alloc(sizeof(TypeExpr)) as *TypeExpr;
+                fte.kind = tekNamed;
+                fte.typeName = ety;
+                fake.refType = fte;
+                Sema_BindPattern(sema, elem, fake);
             }
             elem = elem.patNext;
             ei = ei + 1;
@@ -519,23 +532,25 @@ func Sema_BindPattern(sema: *Sema, pat: *Pattern, subject: *Expr) {
         }
         var field: *Pattern = pat.patArgs;
         while field != null as *Pattern {
-            if field.kind == pkIdent {
-                var ftype: String = "int";
-                if !String_Eq(structName, "") {
-                    let ssym: Symbol = Scope_Lookup(sema.scope, structName);
-                    if ssym.decl != null as *Decl && ssym.decl.kind == dkStruct && ssym.decl.fields != null as *StructField {
-                        var fi: int = 0;
-                        while fi < ssym.decl.fieldCount {
-                            let sf: StructField = ssym.decl.fields[fi];
-                            if String_Eq(sf.name, field.patFieldName) {
-                                if sf.refFieldType != null as *TypeExpr && !String_Eq(sf.refFieldType.typeName, "") {
-                                    ftype = sf.refFieldType.typeName;
-                                }
+            var ftype: String = "int";
+            if !String_Eq(structName, "") {
+                let ssym: Symbol = Scope_Lookup(sema.scope, structName);
+                if ssym.decl != null as *Decl && ssym.decl.kind == dkStruct && ssym.decl.fields != null as *StructField {
+                    var fi: int = 0;
+                    while fi < ssym.decl.fieldCount {
+                        let sf: StructField = ssym.decl.fields[fi];
+                        var fname: String = field.patFieldName;
+                        if String_Eq(fname, "") { fname = field.patIdent; }
+                        if String_Eq(sf.name, fname) {
+                            if sf.refFieldType != null as *TypeExpr && !String_Eq(sf.refFieldType.typeName, "") {
+                                ftype = sf.refFieldType.typeName;
                             }
-                            fi = fi + 1;
                         }
+                        fi = fi + 1;
                     }
                 }
+            }
+            if field.kind == pkIdent {
                 var bsym: Symbol;
                 Sema_ZeroInitSymbol(&bsym);
                 bsym.kind = skVar;
@@ -550,6 +565,13 @@ func Sema_BindPattern(sema: *Sema, pat: *Pattern, subject: *Expr) {
                 bsym.refType = te;
                 bsym.isMutable = false;
                 discard Scope_Define(sema.scope, bsym);
+            } else {
+                let fake: *Expr = bux_alloc(sizeof(Expr)) as *Expr;
+                let fte: *TypeExpr = bux_alloc(sizeof(TypeExpr)) as *TypeExpr;
+                fte.kind = tekNamed;
+                fte.typeName = ftype;
+                fake.refType = fte;
+                Sema_BindPattern(sema, field, fake);
             }
             field = field.patNext;
         }