Introduce pure specifier on functions

7 files changed, 21 insertions, 4 deletions

diff --git a/Changelog.md b/Changelog.md
index 1ea3f6c8..fbbf0761 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,6 +1,7 @@
 ### 0.4.16 (unreleased)
 
 Features:
+ * Introduce ``pure`` functions. The pureness is not enforced yet, use with care.
  * ABI JSON: Include new field ``statemutability`` with values ``view``, ``nonpayable`` and ``payable``.
  * Analyzer: Experimental partial support for Z3 SMT checker.
  * Parser: Display previous visibility specifier in error if multiple are found.
diff --git a/libsolidity/analysis/StaticAnalyzer.cpp b/libsolidity/analysis/StaticAnalyzer.cpp
index ab1cbb52..2f130414 100644
--- a/libsolidity/analysis/StaticAnalyzer.cpp
+++ b/libsolidity/analysis/StaticAnalyzer.cpp
@@ -57,6 +57,8 @@ bool StaticAnalyzer::visit(FunctionDefinition const& _function)
 	solAssert(m_localVarUseCount.empty(), "");
 	m_nonPayablePublic = _function.isPublic() && !_function.isPayable();
 	m_constructor = _function.isConstructor();
+	if (_function.stateMutability() == StateMutability::Pure)
+		m_errorReporter.warning(_function.location(), "Function is marked pure. Be careful, pureness is not enforced yet.");
 	return true;
 }
 
diff --git a/libsolidity/ast/ASTEnums.h b/libsolidity/ast/ASTEnums.h
index f7c75878..5ba21907 100644
--- a/libsolidity/ast/ASTEnums.h
+++ b/libsolidity/ast/ASTEnums.h
@@ -31,12 +31,14 @@ namespace solidity
 {
 
 // How a function can mutate the EVM state.
-enum class StateMutability { View, NonPayable, Payable };
+enum class StateMutability { Pure, View, NonPayable, Payable };
 
 inline std::string stateMutabilityToString(StateMutability const& _stateMutability)
 {
 	switch(_stateMutability)
 	{
+	case StateMutability::Pure:
+		return "pure";
 	case StateMutability::View:
 		return "view";
 	case StateMutability::NonPayable:
diff --git a/libsolidity/interface/ABI.cpp b/libsolidity/interface/ABI.cpp
index 6e8563f7..dd56ff6d 100644
--- a/libsolidity/interface/ABI.cpp
+++ b/libsolidity/interface/ABI.cpp
@@ -36,7 +36,7 @@ Json::Value ABI::generate(ContractDefinition const& _contractDef)
 		method["type"] = "function";
 		method["name"] = it.second->declaration().name();
 		// TODO: deprecate constant in a future release
-		method["constant"] = it.second->stateMutability() == StateMutability::View;
+		method["constant"] = it.second->stateMutability() == StateMutability::Pure || it.second->stateMutability() == StateMutability::View;
 		method["payable"] = it.second->isPayable();
 		method["statemutability"] = stateMutabilityToString(it.second->stateMutability());
 		method["inputs"] = formatTypeList(
diff --git a/libsolidity/parsing/Parser.cpp b/libsolidity/parsing/Parser.cpp
index cd0d6157..ddfdb667 100644
--- a/libsolidity/parsing/Parser.cpp
+++ b/libsolidity/parsing/Parser.cpp
@@ -321,6 +321,8 @@ StateMutability Parser::parseStateMutability(Token::Value _token)
 	// FIXME: constant should be removed at the next breaking release
 	else if (_token == Token::View || _token == Token::Constant)
 		stateMutability = StateMutability::View;
+	else if (_token == Token::Pure)
+		stateMutability = StateMutability::Pure;
 	else
 		solAssert(false, "Invalid state mutability specifier.");
 	m_scanner->next();
diff --git a/libsolidity/parsing/Token.h b/libsolidity/parsing/Token.h
index 3bc52f1d..805fbf5d 100644
--- a/libsolidity/parsing/Token.h
+++ b/libsolidity/parsing/Token.h
@@ -169,6 +169,7 @@ namespace solidity
 	K(Public, "public", 0)                                             \
 	K(Pragma, "pragma", 0)                                             \
 	K(Private, "private", 0)                                           \
+	K(Pure, "pure", 0)                                                 \
 	K(Return, "return", 0)                                             \
 	K(Returns, "returns", 0)                                           \
 	K(Storage, "storage", 0)                                           \
@@ -230,7 +231,6 @@ namespace solidity
 	K(Match, "match", 0)                                               \
 	K(NullLiteral, "null", 0)                                          \
 	K(Of, "of", 0)                                                     \
-	K(Pure, "pure", 0)                                                 \
 	K(Relocatable, "relocatable", 0)                                   \
 	K(Static, "static", 0)                                             \
 	K(Switch, "switch", 0)                                             \
@@ -290,7 +290,7 @@ public:
 	static bool isVisibilitySpecifier(Value op) { return isVariableVisibilitySpecifier(op) || op == External; }
 	static bool isVariableVisibilitySpecifier(Value op) { return op == Public || op == Private || op == Internal; }
 	static bool isLocationSpecifier(Value op) { return op == Memory || op == Storage; }
-	static bool isStateMutabilitySpecifier(Value op) { return op == Constant || op == View || op == Payable; }
+	static bool isStateMutabilitySpecifier(Value op) { return op == Pure || op == Constant || op == View || op == Payable; }
 	static bool isEtherSubdenomination(Value op) { return op == SubWei || op == SubSzabo || op == SubFinney || op == SubEther; }
 	static bool isTimeSubdenomination(Value op) { return op == SubSecond || op == SubMinute || op == SubHour || op == SubDay || op == SubWeek || op == SubYear; }
 	static bool isReservedKeyword(Value op) { return (Abstract <= op && op <= TypeOf); }
diff --git a/test/libsolidity/SolidityParser.cpp b/test/libsolidity/SolidityParser.cpp
index 8e84ead1..a39e0958 100644
--- a/test/libsolidity/SolidityParser.cpp
+++ b/test/libsolidity/SolidityParser.cpp
@@ -928,6 +928,16 @@ BOOST_AUTO_TEST_CASE(multiple_statemutability_specifiers)
 			function f() payable constant {}
 		})";
 	CHECK_PARSE_ERROR(text, "State mutability already specified as \"payable\".");
+	text = R"(
+		contract c {
+			function f() pure payable {}
+		})";
+	CHECK_PARSE_ERROR(text, "State mutability already specified as \"pure\".");
+	text = R"(
+		contract c {
+			function f() pure constant {}
+		})";
+	CHECK_PARSE_ERROR(text, "State mutability already specified as \"pure\".");
 }
 
 BOOST_AUTO_TEST_CASE(literal_constants_with_ether_subdenominations)