stage2: fix inferred comptime constant locals

`const` declarations inside comptime blocks were not getting properly
evaluated at compile-time. To accomplish this there is a new ZIR
instruction, `alloc_inferred_comptime`. Actually we already had one
named that, but it got renamed to `alloc_inferred_comptime_mut` to match
the naming convention with the other similar instructions.

1 files changed, 48 insertions, 0 deletions

diff --git a/test/behavior/null.zig b/test/behavior/null.zig
index 861921d39c..35ecafff80 100644
--- a/test/behavior/null.zig
+++ b/test/behavior/null.zig
@@ -1,3 +1,4 @@
+const builtin = @import("builtin");
 const std = @import("std");
 const expect = std.testing.expect;
 
@@ -140,3 +141,50 @@ const Particle = struct {
     c: u64,
     d: u64,
 };
+
+test "null literal outside function" {
+    const is_null = here_is_a_null_literal.context == null;
+    try expect(is_null);
+
+    const is_non_null = here_is_a_null_literal.context != null;
+    try expect(!is_non_null);
+}
+
+const SillyStruct = struct {
+    context: ?i32,
+};
+
+const here_is_a_null_literal = SillyStruct{ .context = null };
+
+test "unwrap optional which is field of global var" {
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
+
+    struct_with_optional.field = null;
+    if (struct_with_optional.field) |payload| {
+        _ = payload;
+        unreachable;
+    }
+    struct_with_optional.field = 1234;
+    if (struct_with_optional.field) |payload| {
+        try expect(payload == 1234);
+    } else {
+        unreachable;
+    }
+}
+const StructWithOptional = struct {
+    field: ?i32,
+};
+
+var struct_with_optional: StructWithOptional = undefined;
+
+test "optional types" {
+    comptime {
+        const opt_type_struct = StructWithOptionalType{ .t = u8 };
+        try expect(opt_type_struct.t != null and opt_type_struct.t.? == u8);
+    }
+}
+
+const StructWithOptionalType = struct {
+    t: ?type,
+};