libyul: Adds Comment as new AST node type, to be used for pretty printing (and preserving) comments in yul-format.

libsolidity/analysis/ViewPureChecker.cpp

@@ -116,6 +116,10 @@ public:
 			boost::apply_visitor(*this, s);
 	}
 
+	void operator()(yul::Comment const&)
+	{
+	}
+
 private:
 	void checkInstruction(SourceLocation _location, dev::eth::Instruction _instruction)
 	{

libyul/AsmAnalysis.h

@@ -94,6 +94,7 @@ public:
 	bool operator()(Break const&);
 	bool operator()(Continue const&);
 	bool operator()(Block const& _block);
+	bool operator()(Comment const& _comment) { return true; }
 
 private:
 	/// Visits the statement and expects it to deposit one item onto the stack.

libyul/AsmData.h

@@ -82,6 +82,7 @@ struct ForLoop { langutil::SourceLocation location; Block pre; std::unique_ptr<E
 struct Break { langutil::SourceLocation location; };
 /// Continue statement (valid within for loop)
 struct Continue { langutil::SourceLocation location; };
+struct Comment { langutil::SourceLocation location; std::string text; };
 
 struct LocationExtractor: boost::static_visitor<langutil::SourceLocation>
 {

libyul/AsmDataForward.h

@@ -45,10 +45,11 @@ struct Break;
 struct Continue;
 struct ExpressionStatement;
 struct Block;
+struct Comment;
 
 struct TypedName;
 
 using Expression = boost::variant<FunctionalInstruction, FunctionCall, Identifier, Literal>;
-using Statement = boost::variant<ExpressionStatement, Instruction, Label, StackAssignment, Assignment, VariableDeclaration, FunctionDefinition, If, Switch, ForLoop, Break, Continue, Block>;
+using Statement = boost::variant<ExpressionStatement, Instruction, Label, StackAssignment, Assignment, VariableDeclaration, FunctionDefinition, If, Switch, ForLoop, Break, Continue, Block, Comment>;
 
 }

libyul/AsmParser.cpp

@@ -84,8 +84,22 @@ Block Parser::parseBlock()
 	RecursionGuard recursionGuard(*this);
 	Block block = createWithLocation<Block>();
 	expectToken(Token::LBrace);
+
 	while (currentToken() != Token::RBrace)
+	{
+		if (!m_scanner->currentCommentLiteral().empty())
+			block.statements.emplace_back(
+				Comment{m_scanner->currentCommentLocation(), m_scanner->currentCommentLiteral()}
+			);
+
 		block.statements.emplace_back(parseStatement());
+	}
+
+	if (!m_scanner->currentCommentLiteral().empty())
+		block.statements.emplace_back(
+			Comment{m_scanner->currentCommentLocation(), m_scanner->currentCommentLiteral()}
+		);
+
 	block.location.end = endPosition();
 	advance();
 	return block;

libyul/AsmPrinter.cpp

@@ -258,6 +258,12 @@ string AsmPrinter::operator()(Block const& _block) const
 	}
 }
 
+std::string AsmPrinter::operator()(Comment const& _comment) const
+{
+	// Leading newline for better readability of comments.
+	return "\n// " + _comment.text;
+}
+
 string AsmPrinter::formatTypedName(TypedName _variable) const
 {
 	solAssert(!_variable.name.empty(), "Invalid variable name.");

libyul/AsmPrinter.h

@@ -53,6 +53,7 @@ public:
 	std::string operator()(Break const& _break) const;
 	std::string operator()(Continue const& _continue) const;
 	std::string operator()(Block const& _block) const;
+	std::string operator()(Comment const& _comment) const;
 
 private:
 	std::string formatTypedName(TypedName _variable) const;

libyul/AsmScopeFiller.h

@@ -66,6 +66,7 @@ public:
 	bool operator()(Break const&) { return true; }
 	bool operator()(Continue const&) { return true; }
 	bool operator()(Block const& _block);
+	bool operator()(Comment const&) { return true; }
 
 private:
 	bool registerVariable(

libyul/backends/evm/EVMCodeTransform.h

@@ -188,6 +188,7 @@ public:
 	void operator()(Break const&);
 	void operator()(Continue const&);
 	void operator()(Block const& _block);
+	void operator()(Comment const&) {}
 
 private:
 	AbstractAssembly::LabelID labelFromIdentifier(Identifier const& _identifier);

libyul/backends/wasm/EWasmCodeTransform.cpp

@@ -264,7 +264,9 @@ vector<wasm::Expression> EWasmCodeTransform::visit(vector<yul::Statement> const&
 {
 	vector<wasm::Expression> ret;
 	for (auto const& s: _statements)
-		ret.emplace_back(visit(s));
+		if (s.type() != typeid(yul::Comment))
+			ret.emplace_back(visit(s));
+
 	return ret;
 }
 

libyul/backends/wasm/EWasmCodeTransform.h

@@ -54,6 +54,7 @@ public:
 	wasm::Expression operator()(yul::Break const&);
 	wasm::Expression operator()(yul::Continue const&);
 	wasm::Expression operator()(yul::Block const& _block);
+	wasm::Expression operator()(yul::Comment const&) { return {}; }
 
 private:
 	EWasmCodeTransform(

libyul/optimiser/ASTCopier.cpp

@@ -153,6 +153,11 @@ Statement ASTCopier::operator ()(Block const& _block)
 	return translate(_block);
 }
 
+Statement ASTCopier::operator()(Comment const& _comment)
+{
+	return Comment{_comment.location, _comment.text};
+}
+
 Expression ASTCopier::translate(Expression const& _expression)
 {
 	return _expression.apply_visitor(static_cast<ExpressionCopier&>(*this));

libyul/optimiser/ASTCopier.h

@@ -61,6 +61,7 @@ public:
 	virtual Statement operator()(Break const&) = 0;
 	virtual Statement operator()(Continue const&) = 0;
 	virtual Statement operator()(Block const& _block) = 0;
+	virtual Statement operator()(Comment const& _comment) = 0;
 };
 
 /**
@@ -88,6 +89,7 @@ public:
 	Statement operator()(Break const&) override;
 	Statement operator()(Continue const&) override;
 	Statement operator()(Block const& _block) override;
+	Statement operator()(Comment const& _comment) override;
 
 	virtual Expression translate(Expression const& _expression);
 	virtual Statement translate(Statement const& _statement);

libyul/optimiser/ASTWalker.h

@@ -59,6 +59,7 @@ public:
 	virtual void operator()(Break const&) {}
 	virtual void operator()(Continue const&) {}
 	virtual void operator()(Block const& _block);
+	virtual void operator()(Comment const&) {}
 
 	virtual void visit(Statement const& _st);
 	virtual void visit(Expression const& _e);
@@ -96,6 +97,7 @@ public:
 	virtual void operator()(Break&);
 	virtual void operator()(Continue&);
 	virtual void operator()(Block& _block);
+	virtual void operator()(Comment&) {}
 
 	virtual void visit(Statement& _st);
 	virtual void visit(Expression& _e);

libyul/optimiser/SyntacticalEquality.cpp

@@ -181,6 +181,11 @@ bool SyntacticallyEqual::statementEqual(Block const& _lhs, Block const& _rhs)
 	});
 }
 
+bool SyntacticallyEqual::statementEqual(Comment const& _lhs, Comment const& _rhs)
+{
+	return _lhs.text == _rhs.text;
+}
+
 bool SyntacticallyEqual::visitDeclaration(TypedName const& _lhs, TypedName const& _rhs)
 {
 	if (_lhs.type != _rhs.type)

libyul/optimiser/SyntacticalEquality.h

@@ -58,6 +58,7 @@ public:
 	bool statementEqual(Break const&, Break const&) { return true; }
 	bool statementEqual(Continue const&, Continue const&) { return true; }
 	bool statementEqual(Block const& _lhs, Block const& _rhs);
+	bool statementEqual(Comment const& _lhs, Comment const& _rhs);
 private:
 	bool statementEqual(Instruction const& _lhs, Instruction const& _rhs);
 	bool statementEqual(Label const& _lhs, Label const& _rhs);