fix #12740 (#12774)

* fix #12740

* A different kind of a hack

* proper fix

* fix typo

compiler/renderer.nim

@@ -451,7 +451,11 @@ proc lsub(g: TSrcGen; n: PNode): int =
     result = lcomma(g, n, 0, - 3)
     if n[^2].kind != nkEmpty: result = result + lsub(g, n[^2]) + 2
     if n[^1].kind != nkEmpty: result = result + lsub(g, n[^1]) + 3
-  of nkVarTuple: result = lcomma(g, n, 0, - 3) + len("() = ") + lsub(g, lastSon(n))
+  of nkVarTuple:
+    if n[^1].kind == nkEmpty:
+      result = lcomma(g, n, 0, - 2) + len("()")
+    else:
+      result = lcomma(g, n, 0, - 3) + len("() = ") + lsub(g, lastSon(n))
   of nkChckRangeF: result = len("chckRangeF") + 2 + lcomma(g, n)
   of nkChckRange64: result = len("chckRange64") + 2 + lcomma(g, n)
   of nkChckRange: result = len("chckRange") + 2 + lcomma(g, n)
@@ -1119,12 +1123,17 @@ proc gsub(g: var TSrcGen, n: PNode, c: TContext) =
       putWithSpace(g, tkEquals, "=")
       gsub(g, n[^1], c)
   of nkVarTuple:
-    put(g, tkParLe, "(")
-    gcomma(g, n, 0, -3)
-    put(g, tkParRi, ")")
-    put(g, tkSpaces, Space)
-    putWithSpace(g, tkEquals, "=")
-    gsub(g, lastSon(n), c)
+    if n[^1].kind == nkEmpty:
+      put(g, tkParLe, "(")
+      gcomma(g, n, 0, -2)
+      put(g, tkParRi, ")")
+    else:
+      put(g, tkParLe, "(")
+      gcomma(g, n, 0, -3)
+      put(g, tkParRi, ")")
+      put(g, tkSpaces, Space)
+      putWithSpace(g, tkEquals, "=")
+      gsub(g, lastSon(n), c)
   of nkExprColonExpr:
     gsub(g, n, 0)
     putWithSpace(g, tkColon, ":")

tests/macros/tastrepr.nim

@@ -0,0 +1,43 @@
+discard """
+output: '''
+var data = @[(1, "one"), (2, "two")]
+for (i, d) in pairs(data):
+  discard
+for i, d in pairs(data):
+  discard
+for i, (x, y) in pairs(data):
+  discard
+var (a, b) = (1, 2)
+
+var data = @[(1, "one"), (2, "two")]
+for (i, d) in pairs(data):
+  discard
+for i, d in pairs(data):
+  discard
+for i, (x, y) in pairs(data):
+  discard
+var (a, b) = (1, 2)
+'''
+"""
+
+import macros
+
+macro echoTypedRepr(arg: typed) =
+  result = newCall(ident"echo", newLit(arg.repr))
+
+macro echoUntypedRepr(arg: untyped) =
+  result = newCall(ident"echo", newLit(arg.repr))
+
+template echoTypedAndUntypedRepr(arg: untyped) =
+  echoTypedRepr(arg)
+  echoUntypedRepr(arg)
+
+echoTypedAndUntypedRepr:
+  var data = @[(1,"one"), (2,"two")]
+  for (i, d) in pairs(data):
+    discard
+  for i, d in pairs(data):
+    discard
+  for i, (x,y) in pairs(data):
+    discard
+  var (a,b) = (1,2)