fix: Temporary workaround to parse post increments #118

This is a temporary workaround to accept a larger subset of
increments expressions.

src/parser/cxx/parser.cc

@@ -35,7 +35,29 @@
 
 namespace cxx {
 
-static auto getFunctionDeclaratorHelper(DeclaratorAST* declarator)
+namespace {
+
+class RecordingDiagnosticsClient : public DiagnosticsClient {
+ public:
+  void reset() { messages_.clear(); }
+
+  void reportTo(DiagnosticsClient* client) {
+    for (const auto& message : messages_) {
+      client->report(message);
+    }
+  }
+
+  auto messages() const -> const std::vector<Diagnostic>& { return messages_; }
+
+  void report(const Diagnostic& message) override {
+    messages_.push_back(message);
+  }
+
+ private:
+  std::vector<Diagnostic> messages_;
+};
+
+auto getFunctionDeclaratorHelper(DeclaratorAST* declarator)
     -> std::pair<FunctionDeclaratorAST*, bool> {
   if (!declarator) return std::make_pair(nullptr, false);
 
@@ -64,11 +86,13 @@ static auto getFunctionDeclaratorHelper(DeclaratorAST* declarator)
   return std::make_pair(nullptr, false);
 }
 
-static auto getFunctionDeclarator(DeclaratorAST* declarator)
+auto getFunctionDeclarator(DeclaratorAST* declarator)
     -> FunctionDeclaratorAST* {
   return get<0>(getFunctionDeclaratorHelper(declarator));
 }
 
+}  // namespace
+
 Parser::Parser(TranslationUnit* unit) : unit(unit) {
   control = unit->control();
   cursor_ = 1;
@@ -1945,6 +1969,8 @@ auto Parser::parse_unop_expression(ExpressionAST*& yyast) -> bool {
 
   if (!parse_cast_expression(ast->expression)) {
     parse_error("expected an expression");
+    rewind(opLoc);
+    return false;
   }
 
   return true;
@@ -2289,7 +2315,18 @@ auto Parser::parse_delete_expression(ExpressionAST*& yyast) -> bool {
 auto Parser::parse_cast_expression(ExpressionAST*& yyast) -> bool {
   const auto start = currentLocation();
 
-  if (parse_cast_expression_helper(yyast)) return true;
+  RecordingDiagnosticsClient diags;
+
+  auto savedDiagnosticClient = unit->changeDiagnosticsClient(&diags);
+
+  auto parsedCastExpression = parse_cast_expression_helper(yyast);
+
+  unit->changeDiagnosticsClient(savedDiagnosticClient);
+
+  if (parsedCastExpression) {
+    diags.reportTo(unit->diagnosticsClient());
+    return true;
+  }
 
   rewind(start);
 
@@ -2311,7 +2348,9 @@ auto Parser::parse_cast_expression_helper(ExpressionAST*& yyast) -> bool {
 
   ExpressionAST* expression = nullptr;
 
-  if (!parse_cast_expression(expression)) return false;
+  if (!parse_cast_expression(expression)) {
+    return false;
+  }
 
   auto ast = new (pool) CastExpressionAST();
   yyast = ast;

src/parser/cxx/translation_unit.cc

@@ -50,6 +50,16 @@ TranslationUnit::TranslationUnit(Control* control,
 
 TranslationUnit::~TranslationUnit() = default;
 
+auto TranslationUnit::diagnosticsClient() const -> DiagnosticsClient* {
+  return diagnosticsClient_;
+}
+
+auto TranslationUnit::changeDiagnosticsClient(
+    DiagnosticsClient* diagnosticsClient) -> DiagnosticsClient* {
+  std::swap(diagnosticsClient_, diagnosticsClient);
+  return diagnosticsClient;
+}
+
 void TranslationUnit::setSource(std::string source, std::string fileName) {
   fileName_ = std::move(fileName);
   preprocessor_->preprocess(std::move(source), fileName_, tokens_);

src/parser/cxx/translation_unit.h

@@ -48,9 +48,10 @@ class TranslationUnit {
 
   [[nodiscard]] auto arena() const -> Arena* { return arena_.get(); }
 
-  [[nodiscard]] auto diagnosticsClient() const -> DiagnosticsClient* {
-    return diagnosticsClient_;
-  }
+  [[nodiscard]] auto diagnosticsClient() const -> DiagnosticsClient*;
+
+  auto changeDiagnosticsClient(DiagnosticsClient* diagnosticsClient)
+      -> DiagnosticsClient*;
 
   [[nodiscard]] auto ast() const -> UnitAST* { return ast_; }
 

tests/unit_tests/parser/postfix_expr_conflicts.cc

@@ -5,10 +5,7 @@ auto decr(int x) -> int { return x--; }
 auto call(int (*f)(int, int), int x) { return (f)(x, x); }
 auto subscript(int a[], int n) -> int { return a[n]; }
 
-// expected-error@1 {{expected an expression}}
 auto incr_1(int x) -> int { return (x)++; }
-
-// expected-error@1 {{expected an expression}}
 auto decr_1(int x) -> int { return (x)--; }
 
 // expected-error@1 {{expected lambda declarator}}