slice and array re-work plus some misc. changes

 * `@truncate` builtin allows casting to the same size integer.
   It also performs two's complement casting between signed and
   unsigned integers.
 * The idiomatic way to convert between bytes and numbers is now
   `mem.readInt` and `mem.writeInt` instead of an unsafe cast.
   It works at compile time, is safer, and looks cleaner.
 * Implicitly casting an array to a slice is allowed only if the
   slice is const.
 * Constant pointer values know if their memory is from a compile-
   time constant value or a compile-time variable.
 * Cast from [N]u8 to []T no longer allowed, but [N]u8 to []const T
   still allowed.
 * Fix inability to pass a mutable pointer to comptime variable at
   compile-time to a function and have the function modify the
   memory pointed to by the pointer.
 * Add the `comptime T: type` parameter back to mem.eql. Prevents
   accidentally creating instantiations for arrays.

1 files changed, 18 insertions, 0 deletions

diff --git a/test/cases/eval.zig b/test/cases/eval.zig
index 00906488c0..4e7c94f2d3 100644
--- a/test/cases/eval.zig
+++ b/test/cases/eval.zig
@@ -283,3 +283,21 @@ fn callMethodOnBoundFnReferringToVarInstance() {
 
     assert(bound_fn() == 1237);
 }
+
+
+
+fn ptrToLocalArrayArgumentAtComptime() {
+    @setFnTest(this);
+
+    comptime {
+        var bytes: [10]u8 = undefined;
+        modifySomeBytes(bytes[0...]);
+        assert(bytes[0] == 'a');
+        assert(bytes[9] == 'b');
+    }
+}
+
+fn modifySomeBytes(bytes: []u8) {
+    bytes[0] = 'a';
+    bytes[9] = 'b';
+}