From e4b1d8eebcbb176ad0dad509b5b0039fe10de287 Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Fri, 6 Mar 2026 06:08:51 +0800
Subject: [PATCH] fix #25508; ignores void types in the backends (#25550)

fix #25508
---
 compiler/ccgexprs.nim   | 11 ++++++++++-
 compiler/ccgtypes.nim   | 25 +++++++++++++++++++------
 compiler/jsgen.nim      |  6 +++++-
 tests/typerel/tvoid.nim |  5 +++++
 4 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 11fe0673f3..9f2ac2ff9b 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -216,6 +216,8 @@ proc genOptAsgnTuple(p: BProc, dest, src: TLoc, flags: TAssignmentFlags) =
       flags
   let t = skipTypes(dest.t, abstractInst).getUniqueType()
   for i, t in t.ikids:
+    # Do not produce code for void types
+    if isEmptyType(t): continue
     let field = "Field$1" % [i.rope]
     genAssignment(p, optAsgnLoc(dest, t, field),
                      optAsgnLoc(src, t, field), newflags)
@@ -3207,6 +3209,8 @@ proc genTupleConstr(p: BProc, n: PNode, d: var TLoc) =
     for i in 0..<n.len:
       var it = n[i]
       if it.kind == nkExprColonExpr: it = it[1]
+      # Do not produce code for void types
+      if it.typ != nil and isEmptyType(it.typ): continue
       rec = initLoc(locExpr, it, dest[].storage)
       rec.snippet = dotField(rdLoc(dest[]), "Field" & rope(i))
       rec.flags.incl(lfEnforceDeref)
@@ -3818,6 +3822,7 @@ proc containsOpaqueImportcField(typ: PType): bool =
       return true
   of tyTuple:
     for i, a in t.ikids:
+      if isEmptyType(a): continue
       if containsOpaqueImportcField(a):
         return true
   of tyArray:
@@ -3867,10 +3872,12 @@ proc getDefaultValue(p: BProc; typ: PType; info: TLineInfo; result: var Builder)
     var tupleInit: StructInitializer
     let initKind = if containsOpaqueImportcField(t): siNamedStruct else: siOrderedStruct
     result.addStructInitializer(tupleInit, kind = initKind):
-      if p.vccAndC and t.isEmptyTupleType:
+      if p.vccAndC and validTupleTypeFields(t) == 0:
         result.addField(tupleInit, name = "dummy"):
           result.addIntValue(0)
       for i, a in t.ikids:
+        # Do not produce code for void types
+        if isEmptyType(a): continue
         let elemTyp = skipTypes(a, abstractRange+{tyOwned}-{tyTypeDesc})
         if not isOpaqueImportcType(elemTyp):
           result.addField(tupleInit, name = "Field" & $i):
@@ -4045,6 +4052,8 @@ proc genConstTuple(p: BProc, n: PNode; isConst: bool; tup: PType; result: var Bu
       var it = n[i]
       if it.kind == nkExprColonExpr:
         it = it[1]
+      # Do not produce code for void types
+      if isEmptyType(tup[i]): continue
       result.addField(tupleInit, name = "Field" & $i):
         genBracedInit(p, it, isConst, tup[i], result)
 
diff --git a/compiler/ccgtypes.nim b/compiler/ccgtypes.nim
index 79a4dbc1b6..67b7469cb0 100644
--- a/compiler/ccgtypes.nim
+++ b/compiler/ccgtypes.nim
@@ -808,6 +808,8 @@ proc getTupleDesc(m: BModule; typ: PType, name: Rope,
   var res = newBuilder("")
   res.addStruct(m, typ, name, ""):
     for i, a in typ.ikids:
+      # Do not produce code for void types
+      if isEmptyType(a): continue
       res.addField(
         name = "Field" & $i,
         typ = getTypeDescAux(m, a, check, dkField))
@@ -1480,27 +1482,38 @@ proc genObjectInfo(m: BModule; typ, origType: PType, name: Rope; info: TLineInfo
     t.incl tfObjHasKids
     t = t.baseClass
 
+proc validTupleTypeFields(t: PType): int =
+  # we want to treat tuples with only void fields as empty, so we need to exclude void types here:
+  result = 0
+  for a in t.kids:
+    if not isEmptyType(a): inc result
+
 proc genTupleInfo(m: BModule; typ, origType: PType, name: Rope; info: TLineInfo) =
   genTypeInfoAuxBase(m, typ, typ, name, cIntValue(0), info)
   var expr = getNimNode(m)
-  if not typ.isEmptyTupleType:
-    var tmp = getTempName(m) & "_" & $typ.kidsLen
-    genTNimNodeArray(m, tmp, typ.kidsLen)
+  let nonVoidKids = validTupleTypeFields(typ)
+  if nonVoidKids > 0:
+    var tmp = getTempName(m) & "_" & $nonVoidKids
+    genTNimNodeArray(m, tmp, nonVoidKids)
+    var j = 0
     for i, a in typ.ikids:
+      # Do not produce code for void types
+      if isEmptyType(a): continue
       var tmp2 = getNimNode(m)
       let fieldTypInfo = genTypeInfoV1(m, a, info)
-      m.s[cfsTypeInit3].addSubscriptAssignment(tmp, cIntValue(i), cAddr(tmp2))
+      m.s[cfsTypeInit3].addSubscriptAssignment(tmp, cIntValue(j), cAddr(tmp2))
       m.s[cfsTypeInit3].addFieldAssignment(tmp2, "kind", 1)
       m.s[cfsTypeInit3].addFieldAssignmentWithValue(tmp2, "offset"):
         m.s[cfsTypeInit3].addOffsetof(getTypeDesc(m, origType, dkVar), "Field" & $i)
       m.s[cfsTypeInit3].addFieldAssignment(tmp2, "typ", fieldTypInfo)
       m.s[cfsTypeInit3].addFieldAssignment(tmp2, "name", "\"Field" & $i & "\"")
-    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", typ.kidsLen)
+      inc j
+    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", nonVoidKids)
     m.s[cfsTypeInit3].addFieldAssignment(expr, "kind", 2)
     m.s[cfsTypeInit3].addFieldAssignment(expr, "sons",
       cAddr(subscript(tmp, cIntValue(0))))
   else:
-    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", typ.kidsLen)
+    m.s[cfsTypeInit3].addFieldAssignment(expr, "len", cIntValue(0))
     m.s[cfsTypeInit3].addFieldAssignment(expr, "kind", 2)
   m.s[cfsTypeInit3].addFieldAssignment(tiNameForHcr(m, name), "node", cAddr(expr))
 
diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index 99582b0fd6..98153490df 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -2018,8 +2018,12 @@ proc createVar(p: PProc, typ: PType, indirect: bool): Rope =
     if indirect: result = "[$1]" % [result]
   of tyTuple:
     result = rope("{")
+    var first = true
     for i in 0..<t.len:
-      if i > 0: result.add(", ")
+      # Do not produce code for void types
+      if isEmptyType(t[i]): continue
+      if not first: result.add(", ")
+      first = false
       result.addf("Field$1: $2", [i.rope,
             createVar(p, t[i], false)])
     result.add("}")
diff --git a/tests/typerel/tvoid.nim b/tests/typerel/tvoid.nim
index 8bb5691b88..e00f34168d 100644
--- a/tests/typerel/tvoid.nim
+++ b/tests/typerel/tvoid.nim
@@ -4,6 +4,7 @@ empty
 he, no return type;
 abc a string
 ha'''
+  target: "c js"
 """
 
 proc ReturnT[T](x: T): T =
@@ -96,3 +97,7 @@ block: # typeof(stmt)
   block:
     template bad2 = echo (nonexistent; discard)
     doAssert not compiles(bad2())
+
+block:
+  discard default(tuple[b: void])
+  discard default((void,))