Fix shallow for MutRange[T]. (#29)

* Fix shallow for MutRange[T].
Add shallow for slices of Range[T] and MutRange[T].
Add testing procedure.
Add tests.

* Fix appveyor to use status-im nim compiler.

appveyor.yml

@@ -24,13 +24,8 @@ install:
   - IF not exist "%MINGW_ARCHIVE%" appveyor DownloadFile "%MINGW_URL%" -FileName "%MINGW_ARCHIVE%"
   - 7z x -y "%MINGW_ARCHIVE%" > nul
   - SET PATH=%CD%\%MINGW_DIR%\bin;%CD%\Nim\bin;%PATH%
-  - git clone https://github.com/nim-lang/Nim.git
+  - git clone https://github.com/status-im/Nim.git
   - cd %CD%\Nim
-  - git remote add statusim https://github.com/status-im/Nim.git
-  - git fetch statusim
-  - git config --global user.email "you@example.com"
-  - git config --global user.name "Your Name"
-  - for /f "tokens=*" %%G IN ('git branch -a --list ^"statusim/status-autopatch-*^"') DO (git merge %%G)
   - git clone --depth 1 https://github.com/nim-lang/csources
   - cd csources
   - IF "%PLATFORM%" == "x64" ( build64.bat ) else ( build.bat )

ranges/typedranges.nim

@@ -12,7 +12,7 @@ type
     mLen: int
 
   # A view into mutable array
-  MutRange*[T] = distinct Range[T]
+  MutRange* {.shallow.} [T] = distinct Range[T]
 
   ByteRange* = Range[byte]
   MutByteRange* = MutRange[byte]
@@ -129,7 +129,7 @@ proc sliceNormalized[T](r: Range[T], ibegin, iend: int): Range[T] =
                             # an empty range
 
   when rangesGCHoldEnabled:
-    result.gcHold = r.gcHold
+    shallowCopy(result.gcHold, r.gcHold)
   result.start = r.start.shift(ibegin)
   result.mLen = iend - ibegin + 1
 
@@ -169,7 +169,12 @@ proc `[]=`*[T, U, V](r: MutRange[T], s: HSlice[U, V], v: Range[T]) {.inline.} =
   r[s] = toOpenArray(v)
 
 proc baseAddr*[T](r: Range[T]): ptr T {.inline.} = r.start
-
+proc gcHolder*[T](r: Range[T]): ptr T {.inline.} = 
+  ## This procedure is used only for shallow test, do not use it
+  ## in production.
+  when rangesGCHoldEnabled:
+    if r.len > 0:
+      result = unsafeAddr r.gcHold[0]
 template toRange*[T](a: Range[T]): Range[T] = a
 
 # this preferred syntax doesn't work

tests/ttypedranges.nim

@@ -72,8 +72,11 @@ suite "Typed ranges":
     var r2 = r
     s[0] = 5
     check(r[0] == 5)
-    r[1] = 10
+    s[1] = 10
     check(r2[1] == 10)
+    var r3 = r[2..2]
+    s[2] = 15
+    check(r3[0] == 15)
 
   test "hash function":
     var a = toRange(@[1,2,3])
@@ -103,6 +106,34 @@ suite "Typed ranges":
     var a = toRange(@[1,2,3])
     check $a.toOpenArray == "[1, 2, 3]"
 
+  test "MutRange[T] shallow test":
+    var b = @[1, 2, 3, 4, 5, 6]
+    var r1 = b.toRange()
+    var r2 = r1
+    b[0] = 5
+    b[1] = 10
+    b[2] = 15
+    var r3 = r1[1..1]
+    var a0 = cast[uint](addr b[0])
+    var a1 = cast[uint](r1.gcHolder)
+    var a2 = cast[uint](r2.gcHolder)
+    var a3 = cast[uint](r3.gcHolder)
+    check:
+      a1 == a0
+      a2 == a0
+      a3 == a0
+
+  test "Range[T] shallow test":
+    var r1 = toRange(@[1, 2, 3, 4, 5, 6])
+    var r2 = r1
+    var r3 = r1[1..1]
+    var a1 = cast[uint](r1.gcHolder)
+    var a2 = cast[uint](r2.gcHolder)
+    var a3 = cast[uint](r3.gcHolder)
+    check:
+      a2 == a1
+      a3 == a1
+
   test "tryAdvance(Range)":
     var a: Range[int]
     check: