more arc features (#13098)

* config update
* ARC now supports 'repr' and 'new' with finalizers is supported

lib/system/repr_v2.nim

@@ -0,0 +1,170 @@
+proc repr*(x: int): string {.magic: "IntToStr", noSideEffect.}
+  ## repr for an integer argument. Returns `x`
+  ## converted to a decimal string.
+
+proc repr*(x: int64): string {.magic: "Int64ToStr", noSideEffect.}
+  ## repr for an integer argument. Returns `x`
+  ## converted to a decimal string.
+
+proc repr*(x: float): string {.magic: "FloatToStr", noSideEffect.}
+  ## repr for a float argument. Returns `x`
+  ## converted to a decimal string.
+
+proc repr*(x: bool): string {.magic: "BoolToStr", noSideEffect.}
+  ## repr for a boolean argument. Returns `x`
+  ## converted to the string "false" or "true".
+
+proc repr*(x: char): string {.magic: "CharToStr", noSideEffect.}
+  ## repr for a character argument. Returns `x`
+  ## converted to a string.
+  ##
+  ## .. code-block:: Nim
+  ##   assert $'c' == "c"
+
+proc repr*(x: cstring): string {.magic: "CStrToStr", noSideEffect.}
+  ## repr for a CString argument. Returns `x`
+  ## converted to a string.
+
+proc repr*(x: string): string {.magic: "StrToStr", noSideEffect.}
+  ## repr for a string argument. Returns `x`
+  ## as it is. This operator is useful for generic code, so
+  ## that ``$expr`` also works if ``expr`` is already a string.
+
+proc repr*[Enum: enum](x: Enum): string {.magic: "EnumToStr", noSideEffect.}
+  ## repr for an enumeration argument. This works for
+  ## any enumeration type thanks to compiler magic.
+  ##
+  ## If a `repr` operator for a concrete enumeration is provided, this is
+  ## used instead. (In other words: *Overwriting* is possible.)
+
+template repr(t: typedesc): string = $t
+
+proc isNamedTuple(T: typedesc): bool =
+  # Taken from typetraits.
+  when T isnot tuple: result = false
+  else:
+    var t: T
+    for name, _ in t.fieldPairs:
+      when name == "Field0":
+        return compiles(t.Field0)
+      else:
+        return true
+    return false
+
+proc repr*[T: tuple|object](x: T): string =
+  ## Generic `repr` operator for tuples that is lifted from the components
+  ## of `x`. Example:
+  ##
+  ## .. code-block:: Nim
+  ##   $(23, 45) == "(23, 45)"
+  ##   $(a: 23, b: 45) == "(a: 23, b: 45)"
+  ##   $() == "()"
+  when T is object:
+    result = $typeof(x)
+  else:
+    result = ""
+  result.add '('
+  var firstElement = true
+  const isNamed = T is object or isNamedTuple(T)
+  when not isNamed:
+    var count = 0
+  for name, value in fieldPairs(x):
+    if not firstElement: result.add(", ")
+    when isNamed:
+      result.add(name)
+      result.add(": ")
+    else:
+      count.inc
+    when compiles($value):
+      when value isnot string and value isnot seq and compiles(value.isNil):
+        if value.isNil: result.add "nil"
+        else: result.addQuoted(value)
+      else:
+        result.addQuoted(value)
+      firstElement = false
+    else:
+      result.add("...")
+      firstElement = false
+  when not isNamed:
+    if count == 1:
+      result.add(',') # $(1,) should print as the semantically legal (1,)
+  result.add(')')
+
+proc repr*[T: (ref object)](x: T): string =
+  ## Generic `repr` operator for tuples that is lifted from the components
+  ## of `x`.
+  if x == nil: return "nil"
+  result = $typeof(x) & "("
+  var firstElement = true
+  for name, value in fieldPairs(x[]):
+    if not firstElement: result.add(", ")
+    result.add(name)
+    result.add(": ")
+    when compiles($value):
+      when value isnot string and value isnot seq and compiles(value.isNil):
+        if value.isNil: result.add "nil"
+        else: result.addQuoted(value)
+      else:
+        result.addQuoted(value)
+      firstElement = false
+    else:
+      result.add("...")
+      firstElement = false
+  result.add(')')
+
+proc collectionToRepr[T](x: T, prefix, separator, suffix: string): string =
+  result = prefix
+  var firstElement = true
+  for value in items(x):
+    if firstElement:
+      firstElement = false
+    else:
+      result.add(separator)
+
+    when value isnot string and value isnot seq and compiles(value.isNil):
+      # this branch should not be necessary
+      if value.isNil:
+        result.add "nil"
+      else:
+        result.addQuoted(value)
+    else:
+      result.addQuoted(value)
+  result.add(suffix)
+
+proc repr*[T](x: set[T]): string =
+  ## Generic `repr` operator for sets that is lifted from the components
+  ## of `x`. Example:
+  ##
+  ## .. code-block:: Nim
+  ##   ${23, 45} == "{23, 45}"
+  collectionToRepr(x, "{", ", ", "}")
+
+proc repr*[T](x: seq[T]): string =
+  ## Generic `repr` operator for seqs that is lifted from the components
+  ## of `x`. Example:
+  ##
+  ## .. code-block:: Nim
+  ##   $(@[23, 45]) == "@[23, 45]"
+  collectionToRepr(x, "@[", ", ", "]")
+
+proc repr*[T, U](x: HSlice[T, U]): string =
+  ## Generic `repr` operator for slices that is lifted from the components
+  ## of `x`. Example:
+  ##
+  ## .. code-block:: Nim
+  ##  $(1 .. 5) == "1 .. 5"
+  result = $x.a
+  result.add(" .. ")
+  result.add($x.b)
+
+proc repr*[T, IDX](x: array[IDX, T]): string =
+  ## Generic `repr` operator for arrays that is lifted from the components.
+  collectionToRepr(x, "[", ", ", "]")
+
+proc repr*[T](x: openArray[T]): string =
+  ## Generic `repr` operator for openarrays that is lifted from the components
+  ## of `x`. Example:
+  ##
+  ## .. code-block:: Nim
+  ##   $(@[23, 45].toOpenArray(0, 1)) == "[23, 45]"
+  collectionToRepr(x, "[", ", ", "]")