Add legalization for 0-sized arrays. (#7327)

* Add legalization for 0-sized arrays.

* Allow 0-sized arrays in the front-end.

* More tests.

* Add `Conditional<T, hasValue>` type to core module.

* Update toc.

* Fix wording.

* Update test.

1 files changed, 44 insertions, 0 deletions

diff --git a/source/slang/core.meta.slang b/source/slang/core.meta.slang
index 484f51bfc..51e2f326e 100644
--- a/source/slang/core.meta.slang
+++ b/source/slang/core.meta.slang
@@ -1513,6 +1513,50 @@ bool operator!=(__none_t noneVal, Optional<T> val)
     return val.hasValue;
 }
 
+struct Conditional<T, bool hasValue>
+{
+    internal T storage[hasValue];
+
+    __implicit_conversion($(kConversionCost_ValToOptional))
+    [__unsafeForceInlineEarly]
+    __init(T val) { if (hasValue) storage[0] = val;}
+
+    [__unsafeForceInlineEarly]
+    public Optional<T> get()
+    {
+        if (hasValue)
+        {
+            return Optional<T>(storage[0]);
+        }
+        else
+        {
+            return none;
+        }
+    }
+
+    [__unsafeForceInlineEarly]
+    [mutating]
+    public void set(T value)
+    {
+        if (hasValue)
+            storage[0] = value;
+    }
+}
+
+extension<T> Optional<T>
+{
+    __implicit_conversion($(kConversionCost_ImplicitDereference))
+    __generic<bool condHasValue>
+    [__unsafeForceInlineEarly]
+    __init(Conditional<T, condHasValue> condVal)
+    {
+        if (condHasValue)
+            this = Optional<T>(condVal.storage[0]);
+        else
+            this = none;
+    }
+}
+
 //@public:
 
 /// A variadic generic storing the product of several types.