Fix delegate validation to allow any block target (#1748)

This PR makes wabt's validation behavior for `try-delegate` match the spec and spec interpreter. The spec now allows the delegate to target any block, rather than just `try` blocks and the function body block.

The semantics was changed a bit ago as discussed in WebAssembly/exception-handling#176

src/type-checker.cc

@@ -569,10 +569,6 @@ Result TypeChecker::OnDelegate(Index depth) {
   // Delegate starts counting after the current try, as the delegate
   // instruction is not actually in the try block.
   CHECK_RESULT(GetLabel(depth + 1, &label));
-  if (Failed(Check2LabelTypes(label, LabelType::Try, LabelType::Func))) {
-    PrintError("try-delegate must target a try block or function label");
-    result = Result::Error;
-  }
 
   Label* try_label;
   CHECK_RESULT(TopLabel(&try_label));

test/typecheck/try-delegate.txt

@@ -0,0 +1,38 @@
+;;; TOOL: wat2wasm
+;;; ARGS: --enable-exceptions
+(module
+  (tag $e)
+  (func
+    try $l
+      try
+      delegate $l
+    catch $e
+    end)
+
+  (func
+    try $l
+      try
+        try
+        delegate $l
+      catch $e
+      end
+    catch $e
+    end)
+
+  (func
+    block $l
+      try
+      delegate $l
+    end)
+
+  (func
+    try $l
+    catch_all
+      try
+      delegate $l
+    end)
+
+  (func
+    try
+    delegate 0)
+  )