Rewrite wasm-shell to use new wast parser (#6601)

Use the new wast parser to parse a full script up front, then traverse the
parsed script data structure and execute the commands. wasm-shell had previously
used the new wat parser for top-level modules, but it now uses the new parser
for module assertions as well. Fix various bugs this uncovered.

After this change, wasm-shell supports all the assertions used in the upstream
spec tests (although not new kinds of assertions introduced in any proposals).
Uncomment various `assert_exhaustion` tests that we can now execute.

Other kinds of assertions remain commented out in our tests: wasm-shell now
supports `assert_unlinkable`, but the interpreter does not eagerly check for the
existence of imports, so those tests do not pass. Tests that check for NaNs also
remain commented out because they do not yet use the standard syntax that
wasm-shell now supports for canonical and arithmetic NaN results, and our
interpreter would not pass all of those tests even if they did use the standard
syntax.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/parser/lexer.cpp b/src/parser/lexer.cpp
index fd0a262b8..bb6428e87 100644
--- a/src/parser/lexer.cpp
+++ b/src/parser/lexer.cpp
@@ -23,6 +23,7 @@
 #include <variant>
 
 #include "lexer.h"
+#include "support/bits.h"
 #include "support/string.h"
 
 using namespace std::string_view_literals;
@@ -1005,6 +1006,9 @@ std::optional<uint32_t> Lexer::takeAlign() {
     }
     Lexer subLexer(result->span.substr(6));
     if (auto o = subLexer.takeU32()) {
+      if (Bits::popCount(*o) != 1) {
+        return std::nullopt;
+      }
       pos += result->span.size();
       advance();
       return o;