[Parser] Parse tuple types (WebAssembly#6249)

Use the new `(tuple ...)` syntax. Enforce that tuples have a valid number of
elements and are not nested to avoid assertion failures when parsing invalid
input.

Author: tlively

src/parser/contexts.h

@@ -78,6 +78,7 @@ struct TypeUse {
 struct NullTypeParserCtx {
   using IndexT = Ok;
   using HeapTypeT = Ok;
+  using TupleElemListT = Ok;
   using TypeT = Ok;
   using ParamsT = Ok;
   using ResultsT = size_t;
@@ -122,6 +123,10 @@ struct NullTypeParserCtx {
 
   TypeT makeRefType(HeapTypeT, Nullability) { return Ok{}; }
 
+  TupleElemListT makeTupleElemList() { return Ok{}; }
+  void appendTupleElem(TupleElemListT&, TypeT) {}
+  TypeT makeTupleType(TupleElemListT) { return Ok{}; }
+
   ParamsT makeParams() { return Ok{}; }
   void appendParam(ParamsT&, Name, TypeT) {}
 
@@ -219,7 +224,13 @@ template<typename Ctx> struct TypeParserCtx {
     return Type(ht, nullability);
   }
 
-  TypeT makeTupleType(const std::vector<Type> types) { return Tuple(types); }
+  std::vector<Type> makeTupleElemList() { return {}; }
+  void appendTupleElem(std::vector<Type>& elems, Type elem) {
+    elems.push_back(elem);
+  }
+  Result<TypeT> makeTupleType(const std::vector<Type>& types) {
+    return Tuple(types);
+  }
 
   ParamsT makeParams() { return {}; }
   void appendParam(ParamsT& params, Name id, TypeT type) {

src/parser/parsers.h

@@ -28,6 +28,7 @@ using namespace std::string_view_literals;
 // Types
 template<typename Ctx> Result<typename Ctx::HeapTypeT> heaptype(Ctx&);
 template<typename Ctx> MaybeResult<typename Ctx::RefTypeT> reftype(Ctx&);
+template<typename Ctx> MaybeResult<typename Ctx::TypeT> tupletype(Ctx&);
 template<typename Ctx> Result<typename Ctx::TypeT> valtype(Ctx&);
 template<typename Ctx> MaybeResult<typename Ctx::ParamsT> params(Ctx&);
 template<typename Ctx> MaybeResult<typename Ctx::ResultsT> results(Ctx&);
@@ -365,15 +366,34 @@ template<typename Ctx> MaybeResult<typename Ctx::TypeT> reftype(Ctx& ctx) {
   return ctx.makeRefType(*type, nullability);
 }
 
+// tupletype ::= '(' 'tuple' valtype* ')'
+template<typename Ctx> MaybeResult<typename Ctx::TypeT> tupletype(Ctx& ctx) {
+  if (!ctx.in.takeSExprStart("tuple"sv)) {
+    return {};
+  }
+  auto elems = ctx.makeTupleElemList();
+  size_t numElems = 0;
+  while (!ctx.in.takeRParen()) {
+    auto elem = singlevaltype(ctx);
+    CHECK_ERR(elem);
+    ctx.appendTupleElem(elems, *elem);
+    ++numElems;
+  }
+  if (numElems < 2) {
+    return ctx.in.err("tuples must have at least two elements");
+  }
+  return ctx.makeTupleType(elems);
+}
+
 // numtype ::= 'i32' => i32
 //           | 'i64' => i64
 //           | 'f32' => f32
 //           | 'f64' => f64
 // vectype ::= 'v128' => v128
-// valtype ::= t:numtype => t
-//           | t:vectype => t
-//           | t:reftype => t
-template<typename Ctx> Result<typename Ctx::TypeT> valtype(Ctx& ctx) {
+// singlevaltype ::= t:numtype => t
+//                 | t:vectype => t
+//                 | t:reftype => t
+template<typename Ctx> Result<typename Ctx::TypeT> singlevaltype(Ctx& ctx) {
   if (ctx.in.takeKeyword("i32"sv)) {
     return ctx.makeI32();
   } else if (ctx.in.takeKeyword("i64"sv)) {
@@ -392,6 +412,15 @@ template<typename Ctx> Result<typename Ctx::TypeT> valtype(Ctx& ctx) {
   }
 }
 
+// valtype ::= singlevaltype | tupletype
+template<typename Ctx> Result<typename Ctx::TypeT> valtype(Ctx& ctx) {
+  if (auto type = tupletype(ctx)) {
+    CHECK_ERR(type);
+    return *type;
+  }
+  return singlevaltype(ctx);
+}
+
 // param  ::= '(' 'param id? t:valtype ')' => [t]
 //          | '(' 'param t*:valtype* ')' => [t*]
 // params ::= param*

test/lit/wat-kitchen-sink.wast

@@ -457,6 +457,12 @@
  ;; CHECK-NEXT: )
  (func $f4 (type 18) (local i32 i64) (local $l f32))
 
+ ;; CHECK:      (func $tuple-locals (type $void)
+ ;; CHECK-NEXT:  (local $0 (tuple i32 i32))
+ ;; CHECK-NEXT:  (nop)
+ ;; CHECK-NEXT: )
+ (func $tuple-locals (local (tuple i32 i32)))
+
  ;; CHECK:      (func $nop-skate (type $void)
  ;; CHECK-NEXT:  (nop)
  ;; CHECK-NEXT:  (nop)
@@ -3519,7 +3525,7 @@
  (func $ref-func
   ref.func $ref-func
   drop
-  ref.func 151
+  ref.func 152
   drop
  )