[WATParser] Do not clear earlier annotations when lexing annotations (#9143)

Lexer::takeAnnotation called takeKeyword and takeLParen, which are
public token methods that call advance(). Calling advance() executes
annotations.clear(), wiping out any earlier annotations already
collected during the same skipSpace() pass whenever a subsequent
annotation contains a keyword or nested parenthesis. Use peekKeyword() +
take() and takePrefix() instead.

Author: tlively

src/parser/lexer.h

@@ -1113,8 +1113,14 @@ inline std::optional<Annotation> Lexer::takeAnnotation() {
         pos = startPos;
         return std::nullopt;
       }
-      if (takeSpace() || takeKeyword() || takeInteger() || takeFloat() ||
-          takeStr() || takeIdent()) {
+      // Use peekKeyword + take rather than takeKeyword to avoid calling
+      // advance(), which would clear previously collected annotations.
+      if (auto keyword = peekKeyword()) {
+        take(keyword->size());
+        continue;
+      }
+      if (takeSpace() || takeInteger() || takeFloat() || takeStr() ||
+          takeIdent()) {
         continue;
       }
       if (takePrefix("(@"sv)) {
@@ -1130,7 +1136,8 @@ inline std::optional<Annotation> Lexer::takeAnnotation() {
         ++depth;
         continue;
       }
-      if (takeLParen()) {
+      // Use takePrefix rather than takeLParen to avoid calling advance().
+      if (takePrefix("("sv)) {
         ++depth;
         continue;
       }

test/gtest/wat-lexer.cpp

@@ -947,14 +947,17 @@ TEST(LexerTest, LexString) {
 }
 
 TEST(LexerTest, Annotations) {
-  Lexer lexer(
-    "      (@metadata.code.branch_hint \"\\01\")\n      (@metadata.code.branch_hint \"\\00\")\n      (br_if $out"sv);
+  Lexer lexer("(@metadata.code.branch_hint \"\\01\")\n"
+              "(@metadata.code.branch_hint \"\\00\")\n"
+              "(@custom (nested kw))\n"
+              "(br_if $out"sv);
   // Trigger advance/skipSpace which parses annotations.
   lexer.takeID();
   auto annotations = lexer.takeAnnotations();
-  ASSERT_EQ(annotations.size(), 2u);
+  ASSERT_EQ(annotations.size(), 3u);
   EXPECT_EQ(annotations[0].contents, " \"\\01\""sv);
   EXPECT_EQ(annotations[1].contents, " \"\\00\""sv);
+  EXPECT_EQ(annotations[2].contents, " (nested kw)"sv);
 }
 
 TEST(LexerTest, LexKeywords) {