Make try body with multiple instructions roundtrip (#2374)

Previously we didn't print an additional block when there are multiple
instructions within a `try` body, so those wast files cannot be parsed
correctly, because the wast parser assumes there are two bodies within a
`try` scope: a try body and a catch body.

We don't need to print an additional block for a `catch` body because
`(catch ...)` itself serves as a scope.

Author: aheejin

src/passes/Print.cpp

@@ -1768,7 +1768,7 @@ struct PrintSExpression : public OverriddenVisitor<PrintSExpression> {
     o << '(';
     PrintExpressionContents(currFunction, o).visit(curr);
     incIndent();
-    maybePrintImplicitBlock(curr->body, true);
+    maybePrintImplicitBlock(curr->body, false);
     doIndent(o, indent);
     o << "(catch";
     incIndent();

src/wasm/wasm-s-parser.cpp

@@ -1792,7 +1792,7 @@ Expression* SExpressionWasmBuilder::makeTry(Element& s) {
     ret->body = parseExpression(*s[i++]);
   }
   if (!elementStartsWith(*s[i], "catch")) {
-    throw ParseException("catch clause does not exist");
+    throw ParseException("catch clause does not exist", s[i]->line, s[i]->col);
   }
   ret->catchBody = makeCatch(*s[i++]);
   ret->finalize(type);

test/exception-handling.wast

@@ -5,6 +5,9 @@
     (local.get $0)
   )
 
+  (func $foo)
+  (func $bar)
+
   (func $eh_test (local $exn exnref)
     (try
       (throw $e0 (i32.const 0))
@@ -36,5 +39,18 @@
         (drop (exnref.pop))
       )
     )
+
+    ;; Multiple instructions within try and catch bodies
+    (try
+      (block
+        (call $foo)
+        (call $bar)
+      )
+      (catch
+        (drop (exnref.pop))
+        (call $foo)
+        (call $bar)
+      )
+    )
   )
 )

test/exception-handling.wast.from-wast

@@ -6,7 +6,13 @@
  (func $exnref_test (; 0 ;) (type $FUNCSIG$ee) (param $0 exnref) (result exnref)
   (local.get $0)
  )
- (func $eh_test (; 1 ;) (type $FUNCSIG$v)
+ (func $foo (; 1 ;) (type $FUNCSIG$v)
+  (nop)
+ )
+ (func $bar (; 2 ;) (type $FUNCSIG$v)
+  (nop)
+ )
+ (func $eh_test (; 3 ;) (type $FUNCSIG$v)
   (local $exn exnref)
   (try
    (throw $e0
@@ -43,5 +49,18 @@
     )
    )
   )
+  (try
+   (block $block
+    (call $foo)
+    (call $bar)
+   )
+   (catch
+    (drop
+     (exnref.pop)
+    )
+    (call $foo)
+    (call $bar)
+   )
+  )
  )
 )

test/exception-handling.wast.fromBinary

@@ -6,7 +6,13 @@
  (func $exnref_test (; 0 ;) (type $0) (param $0 exnref) (result exnref)
   (local.get $0)
  )
- (func $eh_test (; 1 ;) (type $1)
+ (func $foo (; 1 ;) (type $1)
+  (nop)
+ )
+ (func $bar (; 2 ;) (type $1)
+  (nop)
+ )
+ (func $eh_test (; 3 ;) (type $1)
   (local $0 exnref)
   (try
    (throw $event$0

test/exception-handling.wast.fromBinary.noDebugInfo

@@ -7,6 +7,12 @@
   (local.get $0)
  )
  (func $1 (; 1 ;) (type $1)
+  (nop)
+ )
+ (func $2 (; 2 ;) (type $1)
+  (nop)
+ )
+ (func $3 (; 3 ;) (type $1)
   (local $0 exnref)
   (try
    (throw $event$0

test/try-body-multiple-insts.wasm

@@ -0,0 +1,26 @@
+(module
+ (type $0 (func))
+ (func $0 (; 0 ;) (type $0)
+  (nop)
+ )
+ (func $1 (; 1 ;) (type $0)
+  (nop)
+ )
+ (func $2 (; 2 ;) (type $0)
+  (local $0 exnref)
+  (try
+   (block
+    (call $0)
+    (call $1)
+   )
+   (catch
+    (drop
+     (exnref.pop)
+    )
+    (call $0)
+    (call $1)
+   )
+  )
+ )
+)
+