Add support for inline export/import of tags (#1747)

This PR adds support for inline export/import of tags in modules. e.g.,

```
(tag (import "foo" "bar") (param i32))
```

This is used in the spec tests for the exception handling proposal already:

  https://github.com/WebAssembly/exception-handling/blob/main/test/core/tag.wast

so it would be useful to support in wabt, so that the test suite can be imported in the future.

Author: takikawa

src/wast-parser.cc

@@ -1197,13 +1197,31 @@ Result WastParser::ParseElemModuleField(Module* module) {
 Result WastParser::ParseTagModuleField(Module* module) {
   WABT_TRACE(ParseTagModuleField);
   EXPECT(Lpar);
-  auto field = MakeUnique<TagModuleField>(GetLocation());
   EXPECT(Tag);
-  ParseBindVarOpt(&field->tag.name);
-  CHECK_RESULT(ParseTypeUseOpt(&field->tag.decl));
-  CHECK_RESULT(ParseUnboundFuncSignature(&field->tag.decl.sig));
+  std::string name;
+  ParseBindVarOpt(&name);
+
+  ModuleFieldList export_fields;
+  CHECK_RESULT(ParseInlineExports(&export_fields, ExternalKind::Tag));
+
+  if (PeekMatchLpar(TokenType::Import)) {
+    CheckImportOrdering(module);
+    auto import = MakeUnique<TagImport>(name);
+    CHECK_RESULT(ParseInlineImport(import.get()));
+    CHECK_RESULT(ParseTypeUseOpt(&import->tag.decl));
+    CHECK_RESULT(ParseUnboundFuncSignature(&import->tag.decl.sig));
+    auto field =
+        MakeUnique<ImportModuleField>(std::move(import), GetLocation());
+    module->AppendField(std::move(field));
+  } else {
+    auto field = MakeUnique<TagModuleField>(GetLocation(), name);
+    CHECK_RESULT(ParseTypeUseOpt(&field->tag.decl));
+    CHECK_RESULT(ParseUnboundFuncSignature(&field->tag.decl.sig));
+    module->AppendField(std::move(field));
+  }
+
+  AppendInlineExportFields(module, &export_fields, module->tags.size() - 1);
   EXPECT(Rpar);
-  module->AppendField(std::move(field));
   return Result::Ok;
 }
 

test/parse/module/export-tag.txt

@@ -2,4 +2,5 @@
 ;;; ARGS: --enable-exceptions
 (module
   (tag (param i32 i32))
-  (export "my_tag" (tag 0)))
+  (export "my_tag" (tag 0))
+  (tag (export "my_tag_2") (param i32)))

test/parse/module/import-tag.txt

@@ -1,4 +1,5 @@
 ;;; TOOL: wat2wasm
 ;;; ARGS: --enable-exceptions
 (module
-  (import "foo" "1" (tag (param f64 f32))))
+  (import "foo" "1" (tag (param f64 f32)))
+  (tag $t2 (import "foo" "2") (param i32 i64)))

test/typecheck/bad-tag-results.txt

@@ -3,7 +3,7 @@
 ;;; ERROR: 1
 (module (tag (result i32)))
 (;; STDERR ;;;
-out/test/typecheck/bad-tag-results.txt:4:10: error: Tag signature must have 0 results.
+out/test/typecheck/bad-tag-results.txt:4:14: error: Tag signature must have 0 results.
 (module (tag (result i32)))
-         ^^^
+             ^
 ;;; STDERR ;;)