Disallow unary plus at the parsing stage

Changelog.md

@@ -9,6 +9,7 @@ Compiler Features:
  * NatSpec: Add support for NatSpec documentation in ``enum`` definitions.
  * NatSpec: Add support for NatSpec documentation in ``struct`` definitions.
  * Optimizer: Re-implement simplified version of UnusedAssignEliminator and UnusedStoreEliminator. It can correctly remove some unused assignments in deeply nested loops that were ignored by the old version.
+ * Parser: Unary plus is no longer recognized as a unary operator in the AST and triggers an error at the parsing stage (rather than later during the analysis).
  * SMTChecker: Properties that are proved safe are now reported explicitly at the end of the analysis. By default, only the number of safe properties is shown. The CLI option ``--model-checker-show-proved-safe`` and the JSON option ``settings.modelChecker.showProvedSafe`` can be enabled to show the full list of safe properties.
  * SMTChecker: Group all messages about unsupported language features in a single warning. The CLI option ``--model-checker-show-unsupported`` and the JSON option ``settings.modelChecker.showUnsupported`` can be enabled to show the full list.
  * Yul EVM Code Transform: If available, use ``push0`` instead of ``codesize`` to produce an arbitrary value on stack in order to create equal stack heights between branches.

libsolidity/analysis/SyntaxChecker.cpp

@@ -332,9 +332,7 @@ bool SyntaxChecker::visit(Literal const& _literal)
 
 bool SyntaxChecker::visit(UnaryOperation const& _operation)
 {
-	if (_operation.getOperator() == Token::Add)
-		m_errorReporter.syntaxError(9636_error, _operation.location(), "Use of unary + is disallowed.");
-
+	solAssert(_operation.getOperator() != Token::Add);
 	return true;
 }
 

libsolidity/ast/Types.cpp

@@ -819,16 +819,17 @@ BoolResult FixedPointType::isExplicitlyConvertibleTo(Type const& _convertTo) con
 
 TypeResult FixedPointType::unaryOperatorResult(Token _operator) const
 {
+	solAssert(_operator != Token::Add);
+
 	switch (_operator)
 	{
 	case Token::Delete:
 		// "delete" is ok for all fixed types
 		return TypeResult{TypeProvider::emptyTuple()};
-	case Token::Add:
 	case Token::Sub:
 	case Token::Inc:
 	case Token::Dec:
-		// for fixed, we allow +, -, ++ and --
+		// for fixed, we allow -, ++ and --
 		return this;
 	default:
 		return nullptr;

libsolidity/codegen/ExpressionCompiler.cpp

@@ -511,8 +511,8 @@ bool ExpressionCompiler::visit(UnaryOperation const& _unaryOperation)
 		m_currentLValue.reset();
 		break;
 	case Token::Add: // +
-		// unary add, so basically no-op
-		break;
+		// According to SyntaxChecker...
+		solAssert(false, "Use of unary + is disallowed.");
 	case Token::Sub: // -
 		solUnimplementedAssert(
 			type.category() != Type::Category::FixedPoint,

libsolidity/parsing/Parser.cpp

@@ -1863,6 +1863,10 @@ ASTPointer<Expression> Parser::parseUnaryExpression(
 	ASTNodeFactory nodeFactory = _partiallyParsedExpression ?
 		ASTNodeFactory(*this, _partiallyParsedExpression) : ASTNodeFactory(*this);
 	Token token = m_scanner->currentToken();
+
+	if (token == Token::Add)
+		fatalParserError(9636_error, "Use of unary + is disallowed.");
+
 	if (!_partiallyParsedExpression && (TokenTraits::isUnaryOp(token) || TokenTraits::isCountOp(token)))
 	{
 		// prefix expression

test/libsolidity/syntaxTests/iceRegressionTests/declarationUnaryTuple/declaration_unary_plus_tuple.sol

@@ -0,0 +1,9 @@
+contract C
+{
+    function f() public
+    {
+        int x = +(0, 0);
+    }
+}
+// ----
+// ParserError 9636: (59-60): Use of unary + is disallowed.

test/libsolidity/syntaxTests/iceRegressionTests/declarationUnaryTuple/declaration_unary_tuple.sol

@@ -2,19 +2,15 @@ contract C
 {
     function f() public
     {
-        int x = +(0, 0);
         int y = -(0, 0);
         (int z) = ~(0, 0);
         (int t) = !(0, 0);
     }
 }
 // ----
-// SyntaxError 9636: (59-66): Use of unary + is disallowed.
-// TypeError 4907: (59-66): Built-in unary operator + cannot be applied to type tuple(int_const 0,int_const 0).
+// TypeError 4907: (59-66): Built-in unary operator - cannot be applied to type tuple(int_const 0,int_const 0).
 // TypeError 7364: (51-66): Different number of components on the left hand side (1) than on the right hand side (2).
-// TypeError 4907: (84-91): Built-in unary operator - cannot be applied to type tuple(int_const 0,int_const 0).
-// TypeError 7364: (76-91): Different number of components on the left hand side (1) than on the right hand side (2).
-// TypeError 4907: (111-118): Built-in unary operator ~ cannot be applied to type tuple(int_const 0,int_const 0).
-// TypeError 7364: (101-118): Different number of components on the left hand side (1) than on the right hand side (2).
-// TypeError 4907: (138-145): Built-in unary operator ! cannot be applied to type tuple(int_const 0,int_const 0).
-// TypeError 7364: (128-145): Different number of components on the left hand side (1) than on the right hand side (2).
+// TypeError 4907: (86-93): Built-in unary operator ~ cannot be applied to type tuple(int_const 0,int_const 0).
+// TypeError 7364: (76-93): Different number of components on the left hand side (1) than on the right hand side (2).
+// TypeError 4907: (113-120): Built-in unary operator ! cannot be applied to type tuple(int_const 0,int_const 0).
+// TypeError 7364: (103-120): Different number of components on the left hand side (1) than on the right hand side (2).

test/libsolidity/syntaxTests/nameAndTypeResolution/308_rational_unary_plus_operation.sol

@@ -6,5 +6,4 @@ contract test {
     }
 }
 // ----
-// SyntaxError 9636: (70-75): Use of unary + is disallowed.
-// TypeError 4907: (70-75): Built-in unary operator + cannot be applied to type rational_const 13 / 4.
+// ParserError 9636: (70-71): Use of unary + is disallowed.

test/libsolidity/syntaxTests/parsing/unary_plus_expression.sol

@@ -5,5 +5,4 @@ contract test {
     }
 }
 // ----
-// SyntaxError 9636: (70-72): Use of unary + is disallowed.
-// TypeError 4907: (70-72): Built-in unary operator + cannot be applied to type uint256.
+// ParserError 9636: (70-71): Use of unary + is disallowed.