Fix checking of delegate target block kind. (#1605)

As clarified in:

  WebAssembly/exception-handling#146

the delegate target cannot be a `block` or `loop`. This commit
also adds a failure test that covers several cases discussed
in that issue.

Author: takikawa

src/type-checker.cc

@@ -548,6 +548,10 @@ 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/bad-delegate-target.txt

@@ -0,0 +1,36 @@
+;;; TOOL: wat2wasm
+;;; ERROR: 1
+;;; ARGS: --enable-exceptions
+(module
+  (event $e)
+  (func
+    try
+      block
+        try
+          throw $e
+        delegate 0
+      end
+    catch $e
+    loop
+      try
+        throw $e
+      delegate 0
+    end
+    try
+    catch $e
+      try
+      delegate 0
+    catch_all
+    end
+    end))
+(;; STDERR ;;;
+out/test/typecheck/bad-delegate-target.txt:9:9: error: try-delegate must target a try block or function label
+        try
+        ^^^
+out/test/typecheck/bad-delegate-target.txt:15:7: error: try-delegate must target a try block or function label
+      try
+      ^^^
+out/test/typecheck/bad-delegate-target.txt:21:7: error: try-delegate must target a try block or function label
+      try
+      ^^^
+;;; STDERR ;;)

test/typecheck/delegate.txt

@@ -4,10 +4,11 @@
   (event $e)
   (func
     try
-      block
+      try
         try
           throw $e
         delegate 0
+      catch $e
       end
     catch $e
     end)