[Parser] Parse wast scripts (#6581)

The spec tests use an extension of the standard text format that includes
various commands and assertions used to test WebAssembly implementations. Add a
utility to parse this extended WebAssembly script format and use it in
wasm-shell to check that it parses our spec tests without error. Fix a few
errors the new parser found in our spec tests.

A future PR will rewrite wasm-shell to interpret the results of the new parser,
but for now to keep the diff smaller, do not do anything with the new parser
except check for errors.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/parser/wat-parser.cpp b/src/parser/wat-parser.cpp
index fd18fbbe0..2bc222d6b 100644
--- a/src/parser/wat-parser.cpp
+++ b/src/parser/wat-parser.cpp
@@ -238,7 +238,25 @@ Result<Expression*> parseExpression(Module& wasm, Lexer& lexer) {
   ParseDefsCtx ctx(lexer, wasm, {}, {}, {}, {}, {});
   auto e = expr(ctx);
   CHECK_ERR(e);
+  lexer = ctx.in;
   return *e;
 }
 
+Result<Literal> parseConst(Lexer& lexer) {
+  Module wasm;
+  ParseDefsCtx ctx(lexer, wasm, {}, {}, {}, {}, {});
+  auto inst = foldedinstr(ctx);
+  CHECK_ERR(inst);
+  auto expr = ctx.irBuilder.build();
+  if (auto* err = expr.getErr()) {
+    return lexer.err(err->msg);
+  }
+  auto* e = *expr;
+  if (!e->is<Const>() && !e->is<RefNull>() && !e->is<RefI31>()) {
+    return lexer.err("expected constant");
+  }
+  lexer = ctx.in;
+  return getLiteralFromConstExpression(e);
+}
+
 } // namespace wasm::WATParser