Make capacity work with refc [backport] (#22697)

followup of #19771.

lib/system/seqs_v2.nim

@@ -183,8 +183,6 @@ proc newSeq[T](s: var seq[T], len: Natural) =
 proc sameSeqPayload(x: pointer, y: pointer): bool {.compilerproc, inline.} =
  result = cast[ptr NimRawSeq](x)[].p == cast[ptr NimRawSeq](y)[].p
 
-template capacityImpl(sek: NimSeqV2): int =
- if sek.p != nil: (sek.p.cap and not strlitFlag) else: 0
 
 func capacity*[T](self: seq[T]): int {.inline.} =
  ## Returns the current capacity of the seq.
@@ -194,9 +192,8 @@ func capacity*[T](self: seq[T]): int {.inline.} =
  lst.add "Nim"
  assert lst.capacity == 42
 
- {.cast(noSideEffect).}:
- let sek = unsafeAddr self
- result = capacityImpl(cast[ptr NimSeqV2[T]](sek)[])
+ let sek = cast[ptr NimSeqV2[T]](unsafeAddr self)
+ result = if sek.p != nil: (sek.p.cap and not strlitFlag) else: 0
 
 
 {.pop.} # See https://github.com/nim-lang/Nim/issues/21401

lib/system/strs_v2.nim

@@ -202,9 +202,6 @@ proc prepareMutation*(s: var string) {.inline.} =
  nimPrepareStrMutationV2(cast[ptr NimStringV2](s)[])
 
 
-template capacityImpl(str: NimStringV2): int =
- if str.p != nil: str.p.cap else: 0
-
 func capacity*(self: string): int {.inline.} =
  ## Returns the current capacity of the string.
  # See https://github.com/nim-lang/RFCs/issues/460
@@ -213,6 +210,5 @@ func capacity*(self: string): int {.inline.} =
  str.add "Nim"
  assert str.capacity == 42
 
- {.cast(noSideEffect).}:
- let str = unsafeAddr self
- result = capacityImpl(cast[ptr NimStringV2](str)[])
+ let str = cast[ptr NimStringV2](unsafeAddr self)
+ result = if str.p != nil: str.p.cap else: 0

lib/system/sysstr.nim

@@ -340,3 +340,25 @@ proc setLengthSeqV2(s: PGenericSeq, typ: PNimType, newLen: int): PGenericSeq {.
  result = s
  zeroMem(dataPointer(result, elemAlign, elemSize, result.len), (newLen-%result.len) *% elemSize)
  result.len = newLen
+
+func capacity*(self: string): int {.inline.} =
+ ## Returns the current capacity of the string.
+ # See https://github.com/nim-lang/RFCs/issues/460
+ runnableExamples:
+ var str = newStringOfCap(cap = 42)
+ str.add "Nim"
+ assert str.capacity == 42
+
+ let str = cast[NimString](self)
+ result = if str != nil: str.reserved else: 0
+
+func capacity*[T](self: seq[T]): int {.inline.} =
+ ## Returns the current capacity of the seq.
+ # See https://github.com/nim-lang/RFCs/issues/460
+ runnableExamples:
+ var lst = newSeqOfCap[string](cap = 42)
+ lst.add "Nim"
+ assert lst.capacity == 42
+
+ let sek = cast[PGenericSeq](self)
+ result = if sek != nil: (sek.reserved and not strlitFlag) else: 0