distinctBase type trait for distinct types (#13031)

tests/stdlib/tsugar.nim

@@ -1,37 +0,0 @@
-discard """
-  output: "@[@[], @[], @[], @[], @[]]"
-"""
-import sugar
-import macros
-
-block distinctBase:
-  block:
-    type
-      Foo[T] = distinct seq[T]
-    var a: Foo[int]
-    doAssert a.type.distinctBase is seq[int]
-
-  block:
-    # simplified from https://github.com/nim-lang/Nim/pull/8531#issuecomment-410436458
-    macro uintImpl(bits: static[int]): untyped =
-      if bits >= 128:
-        let inner = getAST(uintImpl(bits div 2))
-        result = newTree(nnkBracketExpr, ident("UintImpl"), inner)
-      else:
-        result = ident("uint64")
-
-    type
-      BaseUint = UintImpl or SomeUnsignedInt
-      UintImpl[Baseuint] = object
-      Uint[bits: static[int]] = distinct uintImpl(bits)
-
-    doAssert Uint[128].distinctBase is UintImpl[uint64]
-
-# bug #7816
-import sequtils
-
-proc tester[T](x: T) =
-  let test = toSeq(0..4).map(i => newSeq[int]())
-  echo test
-
-tester(1)