Improve parser error when encountering extra end delimiter in member …

…list

include/slang/parsing/ParserBase.h

@@ -44,6 +44,8 @@ class SLANG_EXPORT ParserBase {
     Token getLastConsumed() const;
     bool haveDiagAtCurrentLoc();
 
+    const std::pair<Token, Token>& getLastPoppedDelims() const { return lastPoppedDelims; }
+
     Preprocessor& getPP() { return window.tokenSource; }
 
     /// Helper class that maintains a sliding window of tokens, with lookahead.
@@ -236,6 +238,7 @@ class SLANG_EXPORT ParserBase {
     Window window;
     SmallVector<Token> skippedTokens;
     SmallVector<Token> openDelims;
+    std::pair<Token, Token> lastPoppedDelims;
 };
 
 } // namespace slang::parsing

scripts/diagnostics.txt

@@ -298,6 +298,7 @@ error StaticFuncSpecifier "static members cannot have override specifiers"
 error OverridingExtends "'{}' is marked 'extends' but doesn't override a base class virtual member"
 error DerivedCovergroupNotInClass "covergroup inheritance can only be used inside a class"
 error DerivedCovergroupNoBase "covergroup is marked 'extends' but is in a class that has no base class"
+error UnexpectedEndDelim "unexpected '{}' delimiter"
 warning dpi-pure-task DPIPureTask "DPI tasks cannot be marked 'pure'"
 warning nonstandard-generate NonStandardGenBlock "standalone generate block without loop or condition is not allowed in SystemVerilog"
 warning empty-pattern EmptyAssignmentPattern "empty assignment patterns are disallowed by SystemVerilog"
@@ -307,6 +308,8 @@ warning nonstandard-dist NonstandardDist "use of parentheses around 'dist' expre
 warning empty-body EmptyBody "{} has empty body (put the semicolon on a separate line to silence this warning)"
 warning split-distweight-op SplitDistWeightOp "split dist weight operator is not allowed; SystemVerilog requires that they be joined together"
 note NoteToMatchThis "to match this '{}'"
+note NoteLastBlockStarted "last complete block started here"
+note NoteLastBlockEnded "and ended here"
 
 subsystem Declarations
 error LocalParamNoInitializer "local parameter is missing an initializer"

source/parsing/ParserBase.cpp

@@ -77,8 +77,10 @@ Token ParserBase::consume() {
 
     if (SF::isOpenDelimOrKeyword(result.kind))
         openDelims.push_back(result);
-    else if (SF::isCloseDelimOrKeyword(result.kind) && !openDelims.empty())
+    else if (SF::isCloseDelimOrKeyword(result.kind) && !openDelims.empty()) {
+        lastPoppedDelims = {openDelims.back(), result};
         openDelims.pop_back();
+    }
 
     return result;
 }
@@ -107,6 +109,7 @@ Token ParserBase::expect(TokenKind kind) {
             // become unbalanced and flush it.
             openDelims.clear();
         }
+        lastPoppedDelims = {};
     }
 
     Token result = Token::createExpected(alloc, getDiagnostics(), peek(), kind, window.lastConsumed,

source/parsing/Parser_members.cpp

@@ -440,6 +440,18 @@ std::span<TMember*> Parser::parseMemberList(TokenKind endKind, Token& endToken,
             errored = false;
         }
         else {
+            if (isCloseDelimOrKeyword(kind)) {
+                auto& diag = addDiag(diag::UnexpectedEndDelim, peek().range());
+                diag << peek().valueText();
+                errored = true;
+
+                auto& lastBlock = getLastPoppedDelims();
+                if (lastBlock.first && lastBlock.second) {
+                    diag.addNote(diag::NoteLastBlockStarted, lastBlock.first.location());
+                    diag.addNote(diag::NoteLastBlockEnded, lastBlock.second.location());
+                }
+            }
+
             skipToken(errored ? std::nullopt : std::make_optional(diag::ExpectedMember));
             errored = true;
         }

tests/unittests/parsing/MemberParsingTests.cpp

@@ -1458,3 +1458,21 @@ endgroup
     CHECK(diagnostics[4].code == diag::WrongLanguageVersion);
     CHECK(diagnostics[5].code == diag::DerivedCovergroupNotInClass);
 }
+
+TEST_CASE("Parser error recovery with extra end token") {
+    auto& text = R"(
+module m;
+    int i;
+    if (1) begin
+        initial /* begin */
+            i = 1;
+        end
+    end
+endmodule
+)";
+
+    parseCompilationUnit(text);
+
+    REQUIRE(diagnostics.size() == 1);
+    CHECK(diagnostics[0].code == diag::UnexpectedEndDelim);
+}