added a test case ensuring exception inference continues to work

tests/exception/texception_inference.nim

@@ -0,0 +1,32 @@
+discard """
+  output: '''good'''
+  cmd: "nim c --gc:orc -d:release $file"
+"""
+
+type
+  Raising[T, E] = object
+
+proc foo[T, Errors](x: proc (x: Raising[T, Errors])) {.raises: Errors.} =
+  discard
+
+proc callback(x: Raising[int, ValueError]) =
+  echo "callback"
+
+proc xy() {.raises: [ValueError].} =
+  foo callback
+
+proc x[E]() {.raises: [E, IOError].} =
+  raise newException(E, "text here")
+
+try:
+  x[ValueError]()
+except ValueError:
+  echo "good"
+
+proc callback2(x: Raising[int, IOError]) =
+  discard
+
+proc foo2[T, OtherErrors](x: proc(x: Raising[T, OtherErrors])) {.raises: [ValueError, OtherErrors].} =
+  discard
+
+foo2 callback2