fix #25508; ignores void types in the backends (#25550)

fix #25508

(cherry picked from commit e4b1d8eebc)

compiler/ccgexprs.nim

@@ -237,6 +237,8 @@ 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)
@@ -2735,6 +2737,8 @@ 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 = "$1.Field$2" % [rdLoc(dest[]), rope(i)]
       rec.flags.incl(lfEnforceDeref)
@@ -3260,6 +3264,8 @@ proc getDefaultValue(p: BProc; typ: PType; info: TLineInfo; result: var Rope) =
     if p.vccAndC and t.isEmptyTupleType:
       result.add "0"
     for i, a in t.ikids:
+      # Do not produce code for void types
+      if isEmptyType(a): continue
       if i > 0: result.add ", "
       getDefaultValue(p, a, info, result)
     result.add "}"
@@ -3391,6 +3397,8 @@ proc genConstTuple(p: BProc, n: PNode; isConst: bool; tup: PType; result: var Ro
   if p.vccAndC and n.len == 0:
     result.add "0"
   for i in 0..<n.len:
+    # Do not produce code for void types
+    if isEmptyType(tup[i]): continue
     let it = n[i]
     if i > 0: result.add ",\n"
     if it.kind == nkExprColonExpr: genBracedInit(p, it[1], isConst, tup[i], result)

compiler/ccgtypes.nim

@@ -811,6 +811,8 @@ proc getTupleDesc(m: BModule; typ: PType, name: Rope,
   result = newBuilder("")
   result.addStruct(m, typ, name, ""):
     for i, a in typ.ikids:
+      # Do not produce code for void types
+      if isEmptyType(a): continue
       result.addField(
         name = "Field" & $i,
         typ = getTypeDescAux(m, a, check, dkField))
@@ -1423,25 +1425,36 @@ proc genObjectInfo(m: BModule; typ, origType: PType, name: Rope; info: TLineInfo
     t.flags.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, rope("0"), info)
   var expr = getNimNode(m)
-  if not typ.isEmptyTupleType:
-    var tmp = getTempName(m) & "_" & $typ.kidsLen
-    genTNimNodeArray(m, tmp, rope(typ.kidsLen))
+  let nonVoidKids = validTupleTypeFields(typ)
+  if nonVoidKids > 0:
+    var tmp = getTempName(m) & "_" & $nonVoidKids
+    genTNimNodeArray(m, tmp, rope(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)
-      m.s[cfsTypeInit3].addf("$1[$2] = &$3;$n", [tmp, rope(i), tmp2])
+      m.s[cfsTypeInit3].addf("$1[$2] = &$3;$n", [tmp, rope(j), tmp2])
       m.s[cfsTypeInit3].addf("$1.kind = 1;$n" &
           "$1.offset = offsetof($2, Field$3);$n" &
           "$1.typ = $4;$n" &
           "$1.name = \"Field$3\";$n",
            [tmp2, getTypeDesc(m, origType, dkVar), rope(i), genTypeInfoV1(m, a, info)])
+      inc j
     m.s[cfsTypeInit3].addf("$1.len = $2; $1.kind = 2; $1.sons = &$3[0];$n",
-         [expr, rope(typ.kidsLen), tmp])
+         [expr, rope(nonVoidKids), tmp])
   else:
     m.s[cfsTypeInit3].addf("$1.len = $2; $1.kind = 2;$n",
-         [expr, rope(typ.kidsLen)])
+         [expr, rope("0")])
   m.s[cfsTypeInit3].addf("$1.node = &$2;$n", [tiNameForHcr(m, name), expr])
 
 proc genEnumInfo(m: BModule; typ: PType, name: Rope; info: TLineInfo) =

compiler/jsgen.nim

@@ -2004,8 +2004,12 @@ 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("}")

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,))