fix warnings encountered with Nim 1.6 (#128)

* fix warnings encountered with Nim 1.6

* Create shims/stddefects.nim with aliases for all defects

stew/ranges/stackarrays.nim

@@ -37,6 +37,9 @@
 ## be reasonable for short-lived allocations.
 ##
 
+when (NimMajor, NimMinor) < (1, 4):
+  import ../shims/stddefects
+
 type
   StackArray*[T] = object
     bufferLen: int32
@@ -50,7 +53,7 @@ else:
   proc alloca(n: int): pointer {.importc, header: "<alloca.h>".}
 
 proc raiseRangeError(s: string) =
-  raise newException(RangeError, s)
+  raise newException(RangeDefect, s)
 
 proc raiseOutOfRange =
   raiseRangeError "index out of range"

stew/ranges/typedranges.nim

@@ -2,6 +2,10 @@
 
 import ../ptrops, typetraits, hashes
 
+when (NimMajor, NimMinor) < (1, 4):
+  import ../shims/stddefects
+
+
 const rangesGCHoldEnabled = not defined(rangesDisableGCHold)
 const unsafeAPIEnabled* = defined(rangesEnableUnsafeAPI)
 
@@ -159,17 +163,11 @@ proc `[]=`*[T, U, V](r: MutRange[T], s: HSlice[U, V], v: openArray[T]) =
   if L == v.len:
     for i in 0..<L: r[i + a] = v[i]
   else:
-    raise newException(RangeError, "different lengths for slice assignment")
+    raise newException(RangeDefect, "different lengths for slice assignment")
 
 template toOpenArray*[T](r: Range[T]): auto =
-  when false:
-  # when (NimMajor,NimMinor,NimPatch)>=(0,19,9):
-    # error message in Nim HEAD 2019-01-02:
-    # "for a 'var' type a variable needs to be passed, but 'toOpenArray(cast[ptr UncheckedArray[T]](curHash.start), 0, high(curHash))' is immutable"
-    toOpenArray(cast[ptr UncheckedArray[T]](r.start), 0, r.high)
-  else:
-    # NOTE: `0` in `array[0, T]` is irrelevant
-    toOpenArray(cast[ptr array[0, T]](r.start)[], 0, r.high)
+  # NOTE: `0` in `array[0, T]` is irrelevant
+  toOpenArray(cast[ptr array[0, T]](r.start)[], 0, r.high)
 
 proc `[]=`*[T, U, V](r: MutRange[T], s: HSlice[U, V], v: Range[T]) {.inline.} =
   r[s] = toOpenArray(v)
@@ -246,7 +244,7 @@ proc tryAdvance*[T](x: var MutRange[T], idx: int): bool {.inline.} =
 proc advance*[T](x: var Range[T], idx: int) =
   ## Move internal start offset of range ``x`` by ``idx`` elements forward.
   let res = x.advanceImpl(idx)
-  if not res: raise newException(IndexError, "Advance Error")
+  if not res: raise newException(IndexDefect, "Advance Error")
 
 proc advance*[T](x: var MutRange[T], idx: int) {.inline.} =
   ## Move internal start offset of range ``x`` by ``idx`` elements forward.

stew/shims/stddefects.nim

@@ -0,0 +1,23 @@
+when (NimMajor, NimMinor) < (1, 4):
+  type
+    AccessViolationDefect* = AccessViolationError
+    ArithmeticDefect* = ArithmeticError
+    AssertionDefect* = AssertionError
+    DeadThreadDefect* = DeadThreadError
+    DivByZeroDefect* = DivByZeroError
+    FieldDefect* = FieldError
+    FloatDivByZeroDefect* = FloatDivByZeroError
+    FloatInexactDefect* = FloatInexactError
+    FloatInvalidOpDefect* = FloatInvalidOpError
+    FloatOverflowDefect* = FloatOverflowError
+    FloatUnderflowDefect* = FloatUnderflowError
+    FloatingPointDefect* = FloatingPointError
+    IndexDefect* = IndexError
+    NilAccessDefect* = NilAccessError
+    ObjectAssignmentDefect* = ObjectAssignmentError
+    ObjectConversionDefect* = ObjectConversionError
+    OutOfMemDefect* = OutOfMemError
+    OverflowDefect* = OverflowError
+    RangeDefect* = RangeError
+    ReraiseDefect* = ReraiseError
+    StackOverflowDefect* = StackOverflowError

tests/ranges/tstackarrays.nim

@@ -11,6 +11,9 @@ import
   ../../stew/ptrops,
   ../../stew/ranges/[stackarrays]
 
+when (NimMajor, NimMinor) < (1, 4):
+  import ../../stew/shims/stddefects
+
 suite "Stack arrays":
   test "Basic operations work as expected":
     var arr = allocStackArray(int, 10)
@@ -33,14 +36,14 @@ suite "Stack arrays":
       cast[ptr int](offset(addr arr[0], 5))[] == 10
 
   test "Allocating with a negative size throws a RangeError":
-    expect RangeError:
+    expect RangeDefect:
       discard allocStackArray(string, -1)
 
   test "The array access is bounds-checked":
     var arr = allocStackArray(string, 3)
     arr[2] = "test"
     check arr[2] == "test"
-    expect RangeError:
+    expect RangeDefect:
       arr[3] = "another test"
 
   test "proof of stack allocation":

tests/ranges/ttypedranges.nim

@@ -10,6 +10,10 @@ import
   unittest2, sets,
   ../../stew/ranges/[typedranges, ptr_arith]
 
+when (NimMajor, NimMinor) < (1, 4):
+  import ../../stew/shims/stddefects
+
+
 suite "Typed ranges":
   test "basic stuff":
     var r = newRange[int](5)
@@ -169,7 +173,7 @@ suite "Typed ranges":
       try:
         a.advance(b)
         res = 1
-      except IndexError:
+      except IndexDefect:
         res = 2
       res
 
@@ -221,7 +225,7 @@ suite "Typed ranges":
       try:
         a.advance(b)
         res = 1
-      except IndexError:
+      except IndexDefect:
         res = 2
       res