Add support for do/while loops

This commit adds support for a standard do <statement> while <expr>;
form of statement.  While loops were already being supported; supporting
a do/while loop mostly involves reusing code from while loops but putting
the conditional checking last.

Changelog.md

@@ -1,5 +1,8 @@
 ### 0.4.5 (unreleased)
 
+Features:
+ * Do-while loops: support for a C-style do{<block>}while(<expr>); control structure
+
 ### 0.4.4 (2016-10-31)
 
 Bugfixes:

docs/control-structures.rst

@@ -2,14 +2,14 @@
 Expressions and Control Structures
 ##################################
 
-.. index:: if, else, while, for, break, continue, return, switch, goto
+.. index:: if, else, while, do/while, for, break, continue, return, switch, goto
 
 Control Structures
 ===================
 
 Most of the control structures from C or JavaScript are available in Solidity
 except for ``switch`` and ``goto``. So
-there is: ``if``, ``else``, ``while``, ``for``, ``break``, ``continue``, ``return``, ``? :``, with
+there is: ``if``, ``else``, ``while``, ``do``, ``for``, ``break``, ``continue``, ``return``, ``? :``, with
 the usual semantics known from C or JavaScript.
 
 Parentheses can *not* be omitted for conditionals, but curly brances can be omitted

libsolidity/ast/AST.h

@@ -1005,18 +1005,22 @@ class WhileStatement: public BreakableStatement
 		SourceLocation const& _location,
 		ASTPointer<ASTString> const& _docString,
 		ASTPointer<Expression> const& _condition,
-		ASTPointer<Statement> const& _body
+		ASTPointer<Statement> const& _body,
+		bool _isDoWhile
 	):
-		BreakableStatement(_location, _docString), m_condition(_condition), m_body(_body) {}
+		BreakableStatement(_location, _docString), m_condition(_condition), m_body(_body),
+		m_isDoWhile(_isDoWhile) {}
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
 	Expression const& condition() const { return *m_condition; }
 	Statement const& body() const { return *m_body; }
+	bool isDoWhile() const { return m_isDoWhile; }
 
 private:
 	ASTPointer<Expression> m_condition;
 	ASTPointer<Statement> m_body;
+	bool m_isDoWhile;
 };
 
 /**

libsolidity/ast/ASTJsonConverter.cpp

@@ -264,7 +264,11 @@ bool ASTJsonConverter::visit(IfStatement const& _node)
 
 bool ASTJsonConverter::visit(WhileStatement const& _node)
 {
-	addJsonNode(_node, "WhileStatement", {}, true);
+	addJsonNode(
+		_node,
+		_node.isDoWhile() ? "DoWhileStatement" : "WhileStatement",
+		{},
+		true);
 	return true;
 }
 

libsolidity/ast/ASTPrinter.cpp

@@ -208,7 +208,7 @@ bool ASTPrinter::visit(IfStatement const& _node)
 
 bool ASTPrinter::visit(WhileStatement const& _node)
 {
-	writeLine("WhileStatement");
+	writeLine(_node.isDoWhile() ? "DoWhileStatement" : "WhileStatement");
 	printSourcePart(_node);
 	return goDeeper();
 }

libsolidity/codegen/ContractCompiler.cpp

@@ -611,12 +611,25 @@ bool ContractCompiler::visit(WhileStatement const& _whileStatement)
 	m_breakTags.push_back(loopEnd);
 
 	m_context << loopStart;
-	compileExpression(_whileStatement.condition());
-	m_context << Instruction::ISZERO;
-	m_context.appendConditionalJumpTo(loopEnd);
+
+	// While loops have the condition prepended
+	if (!_whileStatement.isDoWhile())
+	{
+		compileExpression(_whileStatement.condition());
+		m_context << Instruction::ISZERO;
+		m_context.appendConditionalJumpTo(loopEnd);
+	}
 
 	_whileStatement.body().accept(*this);
 
+	// Do-while loops have the condition appended
+	if (_whileStatement.isDoWhile())
+	{
+		compileExpression(_whileStatement.condition());
+		m_context << Instruction::ISZERO;
+		m_context.appendConditionalJumpTo(loopEnd);
+	}
+
 	m_context.appendJumpTo(loopStart);
 	m_context << loopEnd;
 

libsolidity/formal/Why3Translator.cpp

@@ -410,6 +410,16 @@ bool Why3Translator::visit(WhileStatement const& _node)
 {
 	addSourceFromDocStrings(_node.annotation());
 
+	// Why3 does not appear to support do-while loops,
+	// so we will simulate them by performing a while
+	// loop with the body prepended once.
+
+	if (_node.isDoWhile())
+	{
+		visitIndentedUnlessBlock(_node.body());
+		newLine();
+	}
+
 	add("while ");
 	_node.condition().accept(*this);
 	newLine();

libsolidity/grammar.txt

@@ -41,7 +41,7 @@ ArrayTypeName = TypeName StorageLocation? '[' Expression? ']'
 StorageLocation = 'memory' | 'storage'
 
 Block = '{' Statement* '}'
-Statement = IfStatement | WhileStatement | ForStatement | Block |
+Statement = IfStatement | WhileStatement | DoWhileStatement | ForStatement | Block |
             ( PlaceholderStatement | Continue | Break | Return |
               Throw | SimpleStatement ) ';'
 
@@ -51,6 +51,7 @@ WhileStatement = 'while' '(' Expression ')' Statement
 PlaceholderStatement = '_'
 SimpleStatement = VariableDefinition | ExpressionStatement
 ForStatement = 'for' '(' (SimpleStatement)? ';' (Expression)? ';' (ExpressionStatement)? ')' Statement
+DoWhileStatement = 'do' Statement 'while' '(' Expression ')' ';'
 Continue = 'continue'
 Break = 'break'
 Return = 'return' Expression?

libsolidity/parsing/Parser.cpp

@@ -722,6 +722,8 @@ ASTPointer<Statement> Parser::parseStatement()
 		return parseIfStatement(docString);
 	case Token::While:
 		return parseWhileStatement(docString);
+	case Token::Do:
+		return parseDoWhileStatement(docString);
 	case Token::For:
 		return parseForStatement(docString);
 	case Token::LBrace:
@@ -816,9 +818,24 @@ ASTPointer<WhileStatement> Parser::parseWhileStatement(ASTPointer<ASTString> con
 	expectToken(Token::RParen);
 	ASTPointer<Statement> body = parseStatement();
 	nodeFactory.setEndPositionFromNode(body);
-	return nodeFactory.createNode<WhileStatement>(_docString, condition, body);
+	return nodeFactory.createNode<WhileStatement>(_docString, condition, body, false);
 }
 
+ASTPointer<WhileStatement> Parser::parseDoWhileStatement(ASTPointer<ASTString> const& _docString)
+{
+	ASTNodeFactory nodeFactory(*this);
+	expectToken(Token::Do);
+	ASTPointer<Statement> body = parseStatement();
+	expectToken(Token::While);
+	expectToken(Token::LParen);
+	ASTPointer<Expression> condition = parseExpression();
+	expectToken(Token::RParen);
+	nodeFactory.markEndPosition();
+	expectToken(Token::Semicolon);
+	return nodeFactory.createNode<WhileStatement>(_docString, condition, body, true);
+}
+
+
 ASTPointer<ForStatement> Parser::parseForStatement(ASTPointer<ASTString> const& _docString)
 {
 	ASTNodeFactory nodeFactory(*this);

libsolidity/parsing/Parser.h

@@ -85,6 +85,7 @@ class Parser: public ParserBase
 	ASTPointer<InlineAssembly> parseInlineAssembly(ASTPointer<ASTString> const& _docString = {});
 	ASTPointer<IfStatement> parseIfStatement(ASTPointer<ASTString> const& _docString);
 	ASTPointer<WhileStatement> parseWhileStatement(ASTPointer<ASTString> const& _docString);
+	ASTPointer<WhileStatement> parseDoWhileStatement(ASTPointer<ASTString> const& _docString);
 	ASTPointer<ForStatement> parseForStatement(ASTPointer<ASTString> const& _docString);
 	/// A "simple statement" can be a variable declaration statement or an expression statement.
 	ASTPointer<Statement> parseSimpleStatement(ASTPointer<ASTString> const& _docString);

test/libsolidity/SolidityEndToEndTest.cpp

@@ -353,6 +353,34 @@ BOOST_AUTO_TEST_CASE(while_loop)
 	testSolidityAgainstCppOnRange("f(uint256)", while_loop_cpp, 0, 5);
 }
 
+
+BOOST_AUTO_TEST_CASE(do_while_loop)
+{
+	char const* sourceCode = "contract test {\n"
+							 "  function f(uint n) returns(uint nfac) {\n"
+							 "    nfac = 1;\n"
+							 "    var i = 2;\n"
+							 "    do { nfac *= i++; } while (i <= n);\n"
+							 "  }\n"
+							 "}\n";
+	compileAndRun(sourceCode);
+
+	auto do_while_loop_cpp = [](u256 const& n) -> u256
+	{
+		u256 nfac = 1;
+		u256 i = 2;
+		do
+		{
+			nfac *= i++;
+		}
+		while (i <= n);
+
+		return nfac;
+	};
+
+	testSolidityAgainstCppOnRange("f(uint256)", do_while_loop_cpp, 0, 5);
+}
+
 BOOST_AUTO_TEST_CASE(nested_loops)
 {
 	// tests that break and continue statements in nested loops jump to the correct place