nrvo don't touch bycopy object

fix nim-lang#19342; Imo nrvo shouldn't touch importc procs

compiler/ccgtypes.nim

@@ -220,7 +220,7 @@ proc isInvalidReturnType(conf: ConfigRef; rettype: PType): bool =
   # such a poor programming language.
   # We exclude records with refs too. This enhances efficiency and
   # is necessary for proper code generation of assignments.
-  if rettype == nil or getSize(conf, rettype) > conf.target.floatSize*3:
+  if rettype == nil or (tfByCopy notin rettype.flags and getSize(conf, rettype) > conf.target.floatSize*3):
     result = true
   else:
     case mapType(conf, rettype, skResult)

tests/objects/m19342.c

@@ -0,0 +1,12 @@
+struct Node
+{
+  int data[25];
+};
+
+
+struct Node hello(int name) {
+  struct Node x = {999, 1, 2, 3, 4, 5, 6, 7, 8, 9,
+            0, 1, 2, 3, 4, 5, 6, 7 ,8, 9,
+            1, 2, 3, 4, 5};
+  return x;
+}

tests/objects/t19342.nim

@@ -0,0 +1,18 @@
+discard """
+  targets: "c cpp"
+"""
+
+{.compile: "m19342.c".}
+
+# bug #19342
+type
+  Node* {.bycopy.} = object
+    data: array[25, cint]
+
+proc myproc(name: cint): Node {.importc: "hello", cdecl.}
+
+proc parse =
+  let node = myproc(10)
+  doAssert node.data[0] == 999
+
+parse()