Support `constref` parameters passing. (#3249)

* Support `constref` parameters passing.

* Fix.

* Fix.

* Add test and diagnostic on mix use of __constref and no_diff.

* check for [constref] on differentiable member method.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

3 files changed, 42 insertions, 4 deletions

diff --git a/tests/diagnostics/const-ref-differentiable-param.slang b/tests/diagnostics/const-ref-differentiable-param.slang
new file mode 100644
index 000000000..c345826e7
--- /dev/null
+++ b/tests/diagnostics/const-ref-differentiable-param.slang
@@ -0,0 +1,38 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK):
+
+
+[Differentiable]
+float f(__constref float3 val)
+{
+    return val.x;
+}
+
+struct MyType : IDifferentiable
+{
+    // Error: cannot use constref on a differentiable member method of a differentiable type.
+    [Differentiable]
+    [constref] float compute(float x) { return 0; }
+
+    // OK
+    [Differentiable]
+    float compute1(float x) { return 0; }
+
+    // OK
+    [constref] float compute2(float x) { return 0;}
+}
+
+struct MyType2
+{
+    // OK.
+    [Differentiable]
+    [constref] float compute(float x) { return 0; }
+
+    // OK
+    [constref]
+    float compute1(float x) { return 0; }
+}
+
+// CHECK-DAG: {{.*}}(5): error 38034: cannot use '__constref' on a differentiable parameter.
+// CHECK-NOT {{.*}}error
+// CHECK-DAG: {{.*}}(14): error 38034: cannot use '[constref]' on a differentiable member method of a differentiable type.
+// CHECK-NOT {{.*}}error
diff --git a/tests/diagnostics/param-mutation.slang b/tests/diagnostics/param-mutation.slang
index 835e645c8..723c4c212 100644
--- a/tests/diagnostics/param-mutation.slang
+++ b/tests/diagnostics/param-mutation.slang
@@ -20,8 +20,6 @@ int doThing(MutatingStruct s, int v)
 
 // For non-copyable types (such as HitObject or NonCopyableStruct declared below), if passed as as `in`
 // should produce an error.
-// NOTE! This *doesn't* produce an error (or warning) because NonCopyable types are *implicitly* 
-// made *ref* when parsed as arguments. 
 
 [__NonCopyableType]
 struct NonCopyableStruct
@@ -32,7 +30,6 @@ struct NonCopyableStruct
 
 int doThing2(NonCopyableStruct s, int v)
 {
-    // Currently doesn't produce an error/warning because NonCopyableStruct is passed as *ref* implicitly.
     s.setValue(v + 1);
     return s.m_value;
 }
diff --git a/tests/diagnostics/param-mutation.slang.expected b/tests/diagnostics/param-mutation.slang.expected
index a1fb34fb7..314d6cbe3 100644
--- a/tests/diagnostics/param-mutation.slang.expected
+++ b/tests/diagnostics/param-mutation.slang.expected
@@ -1,8 +1,11 @@
-result code = 0
+result code = -1
 standard error = {
 tests/diagnostics/param-mutation.slang(17): warning 30068: mutating method 'setValue' called on `in` parameter 's'; changes will not be visible to caller. copy the parameter into a local variable if this behavior is intended
     s.setValue(v + 1);
               ^
+tests/diagnostics/param-mutation.slang(36): error 30067: mutating method 'setValue' called on `in` parameter 's'; changes will not be visible to caller. copy the parameter into a local variable if this behavior is intended
+    s.setValue(v + 1);
+              ^
 }
 standard output = {
 }