backport copy elision changes

This commit contains everything from the copy-elision-2
branch that does not have to do with copy elision directly,
but is generally useful for master branch.

 * All const values know their parents, when applicable, not
   just structs and unions.
 * Null pointers in const values are represented explicitly,
   rather than as a HardCodedAddr value of 0.
 * Rename "maybe" to "optional" in various code locations.
 * Separate DeclVarSrc and DeclVarGen
 * Separate PtrCastSrc and PtrCastGen
 * Separate CmpxchgSrc and CmpxchgGen
 * Represent optional error set as an integer, using the 0 value.
   In a const value, it uses nullptr.
 * Introduce type_has_one_possible_value and use it where applicable.
 * Fix debug builds not setting memory to 0xaa when storing
   undefined.
 * Separate the type of a variable from the const value of a variable.
 * Use copy_const_val where appropriate.
 * Rearrange structs to pack data more efficiently.
 * Move test/cases/* to test/behavior/*
 * Use `std.debug.assertOrPanic` in behavior tests instead of
   `std.debug.assert`.
 * Fix outdated slice syntax in docs.

1 files changed, 0 insertions, 30 deletions

diff --git a/test/cases/void.zig b/test/cases/void.zig
deleted file mode 100644
index 7121ac664b..0000000000
--- a/test/cases/void.zig
+++ /dev/null
@@ -1,30 +0,0 @@
-const assert = @import("std").debug.assert;
-
-const Foo = struct {
-    a: void,
-    b: i32,
-    c: void,
-};
-
-test "compare void with void compile time known" {
-    comptime {
-        const foo = Foo{
-            .a = {},
-            .b = 1,
-            .c = {},
-        };
-        assert(foo.a == {});
-    }
-}
-
-test "iterate over a void slice" {
-    var j: usize = 0;
-    for (times(10)) |_, i| {
-        assert(i == j);
-        j += 1;
-    }
-}
-
-fn times(n: usize) []const void {
-    return ([*]void)(undefined)[0..n];
-}