canonical type equality constraint (#8445)

Fixes #8439

When checked, generic type equality constraints types are now in a
canonical order, allowing for a commutative type equality operator.

---------

Co-authored-by: Mukund Keshava <mkeshava@nvidia.com>

1 files changed, 87 insertions, 0 deletions

diff --git a/tests/language-feature/generics/type-equality-cononical.slang b/tests/language-feature/generics/type-equality-cononical.slang
new file mode 100644
index 000000000..4eb682b10
--- /dev/null
+++ b/tests/language-feature/generics/type-equality-cononical.slang
@@ -0,0 +1,87 @@
+//TEST:SIMPLE(filecheck=CHECK):
+//TEST:INTERPRET(filecheck=ICHECK):
+
+interface MyInterface
+{
+    associatedtype CompatibilityClass;
+
+    __generic <Other : MyInterface>
+    This f(Other other) where Other::CompatibilityClass == This::CompatibilityClass;
+
+    __generic <Other : MyInterface>
+    This g(Other other) where This::CompatibilityClass == Other::CompatibilityClass;
+
+    CompatibilityClass toCompat();
+};
+
+struct MyCompatibilityClass {};
+
+__generic <T>
+struct MyStruct : MyInterface
+{
+    typealias CompatibilityClass = MyCompatibilityClass;
+
+    __generic <Other : MyInterface>
+    This f(Other other) where CompatibilityClass == Other::CompatibilityClass
+    {
+        return this;
+    }
+
+    __generic <Other : MyInterface>
+    This g(Other other) where MyCompatibilityClass == Other::CompatibilityClass
+    {
+        return this;
+    }
+    
+    CompatibilityClass toCompat()
+    {
+        return MyCompatibilityClass();
+    }
+};
+
+struct TestInt : MyInterface
+{
+    typealias CompatibilityClass = int;
+    int value;
+
+    __init(int v)
+    {
+        value = v;
+    }
+
+    __generic <Other : MyInterface>
+    This f(Other other) where CompatibilityClass == Other::CompatibilityClass
+    {
+        return this;
+    }
+
+    __generic <Other : MyInterface>
+    This g(Other other) where int == Other::CompatibilityClass
+    {
+        return this;
+    }
+
+    int toCompat()
+    {
+        return value;
+    }
+}
+
+__generic <T : MyInterface>
+void test(T t)
+    where int == T::CompatibilityClass
+{
+    printf("Success x %d!", t.toCompat());
+}
+
+void main()
+{
+    TestInt t = TestInt(12);
+    test(t);
+}
+
+// CHECK-NOT: 30402
+// CHECK-NOT: 30404
+// CHECK-NOT: 30405
+
+// ICHECK: Success x 12!
\ No newline at end of file