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 * Fix outdated slice syntax in docs.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/switch_prong_err_enum.zig b/test/cases/switch_prong_err_enum.zig
deleted file mode 100644
index 89060690fc..0000000000
--- a/test/cases/switch_prong_err_enum.zig
+++ /dev/null
@@ -1,30 +0,0 @@
-const assert = @import("std").debug.assert;
-
-var read_count: u64 = 0;
-
-fn readOnce() anyerror!u64 {
-    read_count += 1;
-    return read_count;
-}
-
-const FormValue = union(enum) {
-    Address: u64,
-    Other: bool,
-};
-
-fn doThing(form_id: u64) anyerror!FormValue {
-    return switch (form_id) {
-        17 => FormValue{ .Address = try readOnce() },
-        else => error.InvalidDebugInfo,
-    };
-}
-
-test "switch prong returns error enum" {
-    switch (doThing(17) catch unreachable) {
-        FormValue.Address => |payload| {
-            assert(payload == 1);
-        },
-        else => unreachable,
-    }
-    assert(read_count == 1);
-}