feat(selfhost): HirNode.sourceFile for mid-function #line maps

Stamp each HIR node with Decl source path; C backend tracks lastDebugFile
so #line re-emits when file or line changes. Closures inherit the
enclosing function path. Smoke checks Util_Double body maps to Util.bux.

docs/QUALITY_PLAN.md

@@ -1,7 +1,7 @@
 # Bux — План към „добър“ език (v0.5 → v1.0)
 
 > **Дата:** 2026-07-19  
-> **Текущо:** v0.5.x — multi-file #line, selfhost CI, **LSP 0.11 interface hierarchy**, Nexus KA  
+> **Текущо:** v0.5.x — HirNode sourceFile #line, selfhost CI, **LSP 0.12 path rename**, Nexus KA  
 > **Цел:** Език, с който се пишат реални проекти комфортно, безопасно (по избор) и с надежден toolchain.
 
 ---
@@ -740,9 +740,23 @@ A (stdlib ergonomics)  →  B (compiler holes)  →  C (ownership depth)
 
 ---
 
+## Сесия 47 (HirNode-level sourceFile / mid-function #line)
+
+1. **`HirNode.sourceFile`** — per-statement path for `#line` (rare multi-file spans)
+2. **`Lcx_StampSourceFile`**: after lowering a func/closure body, fill empty
+   node paths from `Decl.sourceFile` / `HirFunc.sourceFile` (keeps pre-set paths)
+3. **`LowerCtx.currentSourceFile`** + closures inherit enclosing file
+4. **C backend:** `lastDebugFile` + prefer `node.sourceFile` over func
+   `currentFile`; re-emit `#line` when **line or file** changes mid-function
+5. `BUX_DEBUG_FILE` truly forces one path (no longer overwritten by per-func)
+6. Smoke: `tools/smoke_selfhost.sh` — Util_Double body `#line` → Util.bux only
+7. `make test-selfhost-smoke` / rebuild selfhost
+
+---
+
 ## Следващи стъпки
 
-1. HirNode-level file for statements spanning multiple files (rare)
+1. Optional: selfhost-loop as optional CI job (slow)
-2. Optional: selfhost-loop as optional CI job (slow)
+2. LSP find-implementations request (dedicated, beyond call hierarchy)
-3. LSP find-implementations request (dedicated, beyond call hierarchy)
+3. Workspace-wide import path index without open documents (optional polish)
-4. Workspace-wide import path index without open documents (optional polish)
+4. Expr/Stmt-level sourceFile if macros / cross-file inlining land

src/c_backend.bux

@@ -80,6 +80,7 @@ module CBackend {
         currentRetType: String,
         // #line debug maps (E.4 selfhost parity)
         lastDebugLine: int,
+        lastDebugFile: String,   // re-emit when file changes mid-function (HirNode.sourceFile)
         emitDebugLines: bool,
         currentFile: String,
     }
@@ -140,14 +141,24 @@ module CBackend {
         if node == null as *HirNode { return; }
         if node.line == 0 { return; }
         let ln: int = node.line as int;
-        if ln == cbe.lastDebugLine { return; }
+        // Prefer per-node sourceFile (multi-file spans); else function-level currentFile
+        var file: String = cbe.currentFile;
+        if node.sourceFile != null as String && !String_Eq(node.sourceFile, "") {
+            file = node.sourceFile;
+        }
+        if file == null as String { file = ""; }
+        // Skip only when both line and file unchanged
+        if ln == cbe.lastDebugLine && String_Eq(file, cbe.lastDebugFile) {
+            return;
+        }
         cbe.lastDebugLine = ln;
+        cbe.lastDebugFile = file;
         // #line must start at column 0
         StringBuilder_Append(&cbe.sb, "#line ");
         StringBuilder_AppendInt(&cbe.sb, ln as int64);
-        if !String_Eq(cbe.currentFile, "") {
+        if !String_Eq(file, "") {
             StringBuilder_Append(&cbe.sb, " \"");
-            StringBuilder_Append(&cbe.sb, cbe.currentFile);
+            StringBuilder_Append(&cbe.sb, file);
             StringBuilder_Append(&cbe.sb, "\"");
         }
         StringBuilder_Append(&cbe.sb, "\n");
@@ -1405,6 +1416,7 @@ module CBackend {
         cbe.movedCount = 0;
         cbe.tmpCounter = 0;
         cbe.lastDebugLine = 0;
+        cbe.lastDebugFile = "";
         cbe.emitDebugLines = true;
         cbe.currentFile = "";
         // Optional override for all #line paths (default: per-func Decl.sourceFile)
@@ -1697,12 +1709,17 @@ module CBackend {
                 continue;
             }
             // Per-function source path for multi-file #line (overrides BUX_DEBUG_FILE only if set)
-            if !String_Eq(mod.funcs[i].sourceFile, "") {
+            // BUX_DEBUG_FILE forces one path for the whole unit; skip per-func when set.
-                cbe.currentFile = mod.funcs[i].sourceFile;
+            let forcedDbg: String = bux_getenv("BUX_DEBUG_FILE");
+            if forcedDbg == null as String || String_Eq(forcedDbg, "") {
+                if mod.funcs[i].sourceFile != null as String && !String_Eq(mod.funcs[i].sourceFile, "") {
+                    cbe.currentFile = mod.funcs[i].sourceFile;
+                }
             }
             cbe.lastDebugLine = 0;
+            cbe.lastDebugFile = "";
             // #line before the function itself
-            if cbe.emitDebugLines && !String_Eq(cbe.currentFile, "") {
+            if cbe.emitDebugLines && cbe.currentFile != null as String && !String_Eq(cbe.currentFile, "") {
                 StringBuilder_Append(&cbe.sb, "#line 1 \"");
                 StringBuilder_Append(&cbe.sb, cbe.currentFile);
                 StringBuilder_Append(&cbe.sb, "\"\n");

src/hir.bux

@@ -66,6 +66,9 @@ module Hir {
         // Extra data pointer (for children arrays, field lists, etc.)
         extraData: *void;
         extraCount: int;
+        // Per-node source path for #line (multi-file / rare mid-function spans)
+        // Empty → C backend falls back to HirFunc.sourceFile / currentFile
+        sourceFile: String;
     }
 
     // ---------------------------------------------------------------------------
@@ -182,7 +185,7 @@ module Hir {
             typeKind: 0, typeName: "",
             strValue: "", intValue: 0, boolValue: false,
             child1: null as *HirNode, child2: null as *HirNode, child3: null as *HirNode,
-            extraData: null as *void, extraCount: 0 };
+            extraData: null as *void, extraCount: 0, sourceFile: "" };
     }
 
     func Hir_MakeLit(tokKind: int, tokText: String, line: uint32, col: uint32) -> HirNode {

src/hir_lower.bux

@@ -52,6 +52,33 @@ module HirLower {
         patMapTo6: String,
         patMapFrom7: String,
         patMapTo7: String,
+        // Active source path for #line stamping (from Decl.sourceFile)
+        currentSourceFile: String,
+    }
+
+    /// Fill empty HirNode.sourceFile from `file` (does not overwrite set paths).
+    /// Walks child1/2/3, call arg lists, and if-else via extraData.
+    func Lcx_StampSourceFile(node: *HirNode, file: String) {
+        if node == null as *HirNode { return; }
+        if file == null as String || String_Eq(file, "") { return; }
+        if node.sourceFile == null as String || String_Eq(node.sourceFile, "") {
+            node.sourceFile = file;
+        }
+        Lcx_StampSourceFile(node.child1, file);
+        Lcx_StampSourceFile(node.child2, file);
+        Lcx_StampSourceFile(node.child3, file);
+        // hCall / multi-arg: linked HirArgList in extraData
+        if (node.kind == hCall || node.kind == hCallIndirect) && node.extraData != null as *void {
+            var cur: *HirArgList = node.extraData as *HirArgList;
+            while cur != null as *HirArgList {
+                Lcx_StampSourceFile(cur.node, file);
+                cur = cur.next;
+            }
+        }
+        // hIf else branch may live in extraData (*HirNode)
+        if node.kind == hIf && node.extraData != null as *void {
+            Lcx_StampSourceFile(node.extraData as *HirNode, file);
+        }
     }
 
     func Lcx_PatLookup(ctx: *LowerCtx, src: String) -> String {
@@ -3424,6 +3451,8 @@ module HirLower {
         f.isPublic = decl.isPublic;
         f.checkedFunc = ctx.checkedFunc;
         f.sourceFile = decl.sourceFile;
+        let oldSourceFile: String = ctx.currentSourceFile;
+        ctx.currentSourceFile = decl.sourceFile;
         f.paramCount = decl.paramCount;
         f.param0 = bux_alloc(sizeof(HirParam)) as *HirParam;
         Lcx_LowerParam(f.param0, &decl.param0, ctx);
@@ -3507,12 +3536,16 @@ module HirLower {
         ctx.scope = &funcScope;
         if decl.refBody != null as *Block {
             f.body = Lcx_LowerBlock(ctx, decl.refBody, f.retTypeKind);
+            // Stamp every node with this function's source path (nodes may already
+            // carry a different file for rare multi-file spans; those are kept).
+            Lcx_StampSourceFile(f.body, f.sourceFile);
         } else {
             f.body = null as *HirNode;
         }
         ctx.scope = prevScope;
         ctx.checkedFunc = oldChecked;
         ctx.releaseFunc = oldRelease;
+        ctx.currentSourceFile = oldSourceFile;
 
         return f;
     }
@@ -3528,6 +3561,8 @@ module HirLower {
         let numStr: String = String_FromInt(ctx.funcCount);
         f.name = String_Concat("__closure_", numStr);
         f.isPublic = false;
+        // Closures inherit the enclosing function's source path
+        f.sourceFile = ctx.currentSourceFile;
 
         let params: *Decl = expr.closureParams;
         // Fat-func ABI: leading void* __env, then user params
@@ -3641,6 +3676,7 @@ module HirLower {
         ctx.envInstanceName = envInstanceName;
         if expr.refBlock != null as *Block {
             f.body = Lcx_LowerBlock(ctx, expr.refBlock, -1);
+            Lcx_StampSourceFile(f.body, f.sourceFile);
         } else {
             f.body = null as *HirNode;
         }

tools/smoke_selfhost.sh

@@ -108,4 +108,34 @@ if ! grep -qE '#line [0-9]+ ".*lib/.*\.bux"' "$MAIN_C"; then
 fi
 echo "  multi-file #line: PASS (Util + Main + lib)"
 
-echo "PASS: selfhost smoke (move_field + multi-file #line)"
+# ---------------------------------------------------------------------------
+# 3) HirNode-level sourceFile — statement #line inside Util_Double uses Util.bux
+#    (not only the function prolog), and never Main.bux inside that body.
+# ---------------------------------------------------------------------------
+echo "=== selfhost: HirNode sourceFile (#line in body) ==="
+# Function definition (not the forward decl): #line 1 "…Util.bux" then int Util_Double(
+util_body=$(awk '
+  /#line 1 ".*Util\.bux"/ { grab=1 }
+  grab { print }
+  grab && /^}/ { exit }
+' "$MAIN_C")
+if [[ -z "$util_body" ]]; then
+  echo "error: could not find Util_Double definition block" >&2
+  grep -n 'Util_Double\|Util\.bux' "$MAIN_C" | head -20
+  exit 1
+fi
+# Statement-level #line inside body (not only prolog #line 1) must point at Util.bux
+if ! echo "$util_body" | grep -vE '#line 1 "' | grep -qE '#line [0-9]+ ".*Util\.bux"'; then
+  echo "error: Util_Double body has no statement #line …Util.bux" >&2
+  echo "$util_body"
+  exit 1
+fi
+# Body of Util_Double must not claim Main.bux
+if echo "$util_body" | grep -qE '#line [0-9]+ ".*Main\.bux"'; then
+  echo "error: Util_Double body has #line Main.bux (wrong sourceFile)" >&2
+  echo "$util_body" | grep -E '#line '
+  exit 1
+fi
+echo "  HirNode sourceFile: PASS (Util_Double stmts → Util.bux)"
+
+echo "PASS: selfhost smoke (move_field + multi-file #line + HirNode sourceFile)"