Support custom backward derivative attribute. (#2594)

2 files changed, 23 insertions, 0 deletions

diff --git a/tests/language-server/robustness-6.slang b/tests/language-server/robustness-6.slang
new file mode 100644
index 000000000..ef5924cf3
--- /dev/null
+++ b/tests/language-server/robustness-6.slang
@@ -0,0 +1,10 @@
+//TEST:LANG_SERVER:
+//HOVER:4,8
+
+float dsqr<T:II
+
+[ForwardDerivative(dsqr)]
+float sqr<T:IInterface>(T obj, float x)
+{
+    return no_diff(obj.calc(x)) + x * x;
+}
diff --git a/tests/language-server/robustness-6.slang.expected.txt b/tests/language-server/robustness-6.slang.expected.txt
new file mode 100644
index 000000000..d5aa6c8c9
--- /dev/null
+++ b/tests/language-server/robustness-6.slang.expected.txt
@@ -0,0 +1,13 @@
+--------
+range: 3,6 - 3,10
+content:
+```
+func dsqr<T>(T obj, float x) -> float
+```
+
+TEST:LANG_SERVER:  
+HOVER:4,8  
+
+{REDACTED}.slang(4)
+
+