[Parser] Begin parsing modules (#4716)

Implement the basic infrastructure for the full WAT parser with just enough
detail to parse basic modules that contain only imported globals. Parsing
functions correspond to elements of the grammar in the text specification and
are templatized over context types that correspond to each phase of parsing.
Errors are explicitly propagated via `Result<T>` and `MaybeResult<T>` types.

Follow-on PRs will implement additional phases of parsing and parsing for new
elements in the grammar.

1 files changed, 16 insertions, 4 deletions

diff --git a/src/wasm/wasm-io.cpp b/src/wasm/wasm-io.cpp
index b94fc8470..55892975b 100644
--- a/src/wasm/wasm-io.cpp
+++ b/src/wasm/wasm-io.cpp
@@ -24,19 +24,31 @@
 // binary.
 //
 
-#include "wasm-io.h"
 #include "support/debug.h"
 #include "wasm-binary.h"
 #include "wasm-s-parser.h"
+#include "wat-parser.h"
+
+#include "wasm-io.h"
 
 namespace wasm {
 
+bool useNewWATParser = false;
+
 #define DEBUG_TYPE "writer"
 
 static void readTextData(std::string& input, Module& wasm, IRProfile profile) {
-  SExpressionParser parser(const_cast<char*>(input.c_str()));
-  Element& root = *parser.root;
-  SExpressionWasmBuilder builder(wasm, *root[0], profile);
+  if (useNewWATParser) {
+    std::string_view in(input.c_str());
+    if (auto parsed = WATParser::parseModule(wasm, in);
+        auto err = parsed.getErr()) {
+      Fatal() << err->msg;
+    }
+  } else {
+    SExpressionParser parser(const_cast<char*>(input.c_str()));
+    Element& root = *parser.root;
+    SExpressionWasmBuilder builder(wasm, *root[0], profile);
+  }
 }
 
 void ModuleReader::readText(std::string filename, Module& wasm) {