Introduce RightArrow (->) token in the scanner

Changelog.md

@@ -15,6 +15,7 @@ Compiler Features:
 Bugfixes:
  * AST: Remove ``null`` member values also when the compiler is used in standard-json-mode.
  * Optimizer: Keep side-effects of ``x`` in ``byte(a, shr(b, x))`` even if the constants ``a`` and ``b`` would make the expression zero unconditionally. This optimizer rule is very hard if not impossible to trigger in a way that it can result in invalid code, though.
+ * Scanner: Fix bug where whitespace would be allowed within the ``->`` token (e.g. ``function f() -   > x {}`` becomes invalid in inline assembly and Yul).
  * SMTChecker: Fix internal error in BMC function inlining.
  * SMTChecker: Fix internal error on array implicit conversion.
  * SMTChecker: Fix internal error on fixed bytes index access.

docs/grammar/SolidityLexer.g4

@@ -112,6 +112,7 @@ Semicolon: ';';
 Period: '.';
 Conditional: '?';
 Arrow: '=>';
+RightArrow: '->';
 
 Assign: '=';
 AssignBitOr: '|=';
@@ -283,9 +284,7 @@ YulRParen: ')';
 YulAssign: ':=';
 YulPeriod: '.';
 YulComma: ',';
-// TODO: remove whitespace workaround once the parser disallows it.
+YulArrow: '->';
-//@doc:name ->
-YulArrow: '->' | '-' YulWS+ '>';
 
 /**
  * Yul identifiers consist of letters, dollar signs, underscores and numbers, but may not start with a number.

liblangutil/Scanner.cpp

@@ -563,12 +563,14 @@ void Scanner::scanToken()
 				token = Token::Add;
 			break;
 		case '-':
-			// - -- -=
+			// - -- -= ->
 			advance();
 			if (m_char == '-')
 				token = selectToken(Token::Dec);
 			else if (m_char == '=')
 				token = selectToken(Token::AssignSub);
+			else if (m_char == '>')
+				token = selectToken(Token::RightArrow);
 			else
 				token = Token::Sub;
 			break;

liblangutil/Token.h

@@ -84,6 +84,7 @@ namespace solidity::langutil
 	T(Period, ".", 0)                                                   \
 	T(Conditional, "?", 3)                                              \
 	T(Arrow, "=>", 0)                                                   \
+	T(RightArrow, "->", 0)                                              \
 	\
 	/* Assignment operators. */										\
 	/* IsAssignmentOp() relies on this block of enum values being */	\

libyul/AsmParser.cpp

@@ -401,10 +401,9 @@ FunctionDefinition Parser::parseFunctionDefinition()
 		expectToken(Token::Comma);
 	}
 	expectToken(Token::RParen);
-	if (currentToken() == Token::Sub)
+	if (currentToken() == Token::RightArrow)
 	{
-		expectToken(Token::Sub);
+		expectToken(Token::RightArrow);
-		expectToken(Token::GreaterThan);
 		while (true)
 		{
 			funDef.returnVariables.emplace_back(parseTypedName());

test/liblangutil/Scanner.cpp

@@ -782,8 +782,7 @@ BOOST_AUTO_TEST_CASE(yul_function)
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Comma);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Identifier);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::RParen);
-	BOOST_CHECK_EQUAL(scanner.next(), Token::Sub);
+	BOOST_CHECK_EQUAL(scanner.next(), Token::RightArrow);
-	BOOST_CHECK_EQUAL(scanner.next(), Token::GreaterThan);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Identifier);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Comma);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Identifier);
@@ -797,8 +796,7 @@ BOOST_AUTO_TEST_CASE(yul_function)
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Comma);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Identifier);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::RParen);
-	BOOST_CHECK_EQUAL(scanner.next(), Token::Sub);
+	BOOST_CHECK_EQUAL(scanner.next(), Token::RightArrow);
-	BOOST_CHECK_EQUAL(scanner.next(), Token::GreaterThan);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Identifier);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Comma);
 	BOOST_CHECK_EQUAL(scanner.next(), Token::Identifier);

test/libsolidity/syntaxTests/inlineAssembly/function_definition_whitespace.sol

@@ -6,3 +6,5 @@ contract C {
     }
   }
 }
+// ----
+// ParserError 2314: (87-88): Expected '{' but got '-'

test/libyul/yulSyntaxTests/function_definition_whitespace.yul

@@ -2,3 +2,5 @@
     function f (a, b  , c ) -     >    y,x,z {
     }
 }
+// ----
+// ParserError 2314: (30-31): Expected '{' but got '-'