Destructors: move into nkTupleConstr and move on tuple unpacking (#9776)

compiler/destroyer.nim

@@ -261,6 +261,11 @@ proc isLastRead(n: PNode; c: var Con): bool =
 template interestingSym(s: PSym): bool =
   s.owner == c.owner and s.kind in InterestingSyms and hasDestructor(s.typ)
 
+template isUnpackedTuple(s: PSym): bool =
+  ## we move out all elements of unpacked tuples, 
+  ## hence unpacked tuples themselves don't need to be destroyed
+  s.kind == skTemp and s.typ.kind == tyTuple
+
 proc patchHead(n: PNode) =
   if n.kind in nkCallKinds and n[0].kind == nkSym and n.len > 1:
     let s = n[0].sym
@@ -446,6 +451,13 @@ proc moveOrCopy(dest, ri: PNode; c: var Con): PNode =
       ri2.add pArg(ri[i], c, i < L and parameters[i].kind == tySink)
     #recurse(ri, ri2)
     result.add ri2
+  of nkBracketExpr:
+    if ri[0].kind == nkSym and isUnpackedTuple(ri[0].sym):
+      # unpacking of tuple: move out the elements 
+      result = genSink(c, dest.typ, dest, ri)
+    else:
+      result = genCopy(c, dest.typ, dest, ri)
+    result.add p(ri, c)
   of nkObjConstr:
     result = genSink(c, dest.typ, dest, ri)
     let ri2 = copyTree(ri)
@@ -454,6 +466,17 @@ proc moveOrCopy(dest, ri: PNode; c: var Con): PNode =
       # so these all act like 'sink' parameters:
       ri2[i].sons[1] = pArg(ri[i][1], c, isSink = true)
     result.add ri2
+  of nkTupleConstr:
+    result = genSink(c, dest.typ, dest, ri)
+    let ri2 = copyTree(ri)
+    for i in 0..<ri.len:
+      # everything that is passed to an tuple constructor is consumed,
+      # so these all act like 'sink' parameters:
+      if ri[i].kind == nkExprColonExpr:
+        ri2[i].sons[1] = pArg(ri[i][1], c, isSink = true)
+      else:
+        ri2[i] = pArg(ri[i], c, isSink = true)
+    result.add ri2
   of nkSym:
     if ri.sym.kind != skParam and isLastRead(ri, c):
       # Rule 3: `=sink`(x, z); wasMoved(z)
@@ -483,7 +506,7 @@ proc p(n: PNode; c: var Con): PNode =
       if it.kind == nkVarTuple and hasDestructor(ri.typ):
         let x = lowerTupleUnpacking(c.graph, it, c.owner)
         result.add p(x, c)
-      elif it.kind == nkIdentDefs and hasDestructor(it[0].typ):
+      elif it.kind == nkIdentDefs and hasDestructor(it[0].typ) and not isUnpackedTuple(it[0].sym):
         for j in 0..L-2:
           let v = it[j]
           doAssert v.kind == nkSym

tests/destructor/t6434.nim

@@ -1,21 +1,26 @@
 discard """
   exitcode: 0
-  output: '''assingment
-assingment
-assingment
-assingment
-'''
+  output: ""
 """
 
 type
   Foo* = object
     boo: int
 
+var sink_counter = 0
+var assign_counter = 0
+
+proc `=sink`(dest: var Foo, src: Foo) =
+  sink_counter.inc
+
 proc `=`(dest: var Foo, src: Foo) =
-  debugEcho "assingment"
+  assign_counter.inc
 
 proc test(): auto =
   var a,b : Foo
-  return (a, b)
+  return (a, b, Foo(boo: 5))
 
-var (a, b) = test()
+var (a, b, _) = test()
+
+doAssert: assign_counter == 0
+doAssert: sink_counter == 9

tests/destructor/tmove_objconstr.nim

@@ -60,3 +60,62 @@ for x in getPony():
 # XXX this needs to be enabled once top level statements
 # produce destructor calls again.
 #echo "Pony is dying!"
+
+
+#------------------------------------------------------------
+#-- Move into tuple constructor and move on tuple unpacking
+#------------------------------------------------------------
+
+type
+  MySeqNonCopyable* = object
+    len: int 
+    data: ptr UncheckedArray[float]
+
+proc `=destroy`*(m: var MySeqNonCopyable) {.inline.} =
+  if m.data != nil:
+    deallocShared(m.data)
+    m.data = nil
+
+proc `=`*(m: var MySeqNonCopyable, m2: MySeqNonCopyable) {.error.}
+
+proc `=sink`*(m: var MySeqNonCopyable, m2: MySeqNonCopyable) {.inline.} =
+  if m.data != m2.data:
+    if m.data != nil:
+      `=destroy`(m)
+    m.len = m2.len
+    m.data = m2.data
+
+proc len*(m: MySeqNonCopyable): int {.inline.} = m.len
+
+proc `[]`*(m: MySeqNonCopyable; i: int): float {.inline.} =
+  m.data[i.int]
+
+proc `[]=`*(m: var MySeqNonCopyable; i, val: float) {.inline.} =
+  m.data[i.int] = val
+
+proc setTo(s: var MySeqNonCopyable, val: float) = 
+  for i in 0..<s.len.int:
+    s.data[i] = val
+
+proc newMySeq*(size: int, initial_value = 0.0): MySeqNonCopyable =#
+  result.len = size
+  if size > 0:
+    result.data = cast[ptr UncheckedArray[float]](createShared(float, size))
+
+  result.setTo(initial_value)
+
+proc myfunc(x, y: int): (MySeqNonCopyable, MySeqNonCopyable) =
+  result = (newMySeq(x, 1.0), newMySeq(y, 5.0))
+
+proc myfunc2(x, y: int): tuple[a: MySeqNonCopyable, b:int, c:MySeqNonCopyable] =
+  (a: newMySeq(x, 1.0), b:0, c:newMySeq(y, 5.0))
+
+let (seq1, seq2) = myfunc(2, 3)
+doAssert seq1.len == 2
+doAssert seq1[0] == 1.0
+doAssert seq2.len == 3
+doAssert seq2[0] == 5.0
+
+var (seq3, i, _) = myfunc2(2, 3)
+doAssert seq3.len == 2
+doAssert seq3[0] == 1.0