Merge pull request #677 from chriseth/unusedReturn

Warn about unused return values.

3 files changed, 102 insertions, 0 deletions

diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index ce55de00..6b2c1cb8 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -830,6 +830,22 @@ void TypeChecker::endVisit(ExpressionStatement const& _statement)
 	if (type(_statement.expression())->category() == Type::Category::RationalNumber)
 		if (!dynamic_cast<RationalNumberType const&>(*type(_statement.expression())).mobileType())
 			typeError(_statement.expression().location(), "Invalid rational number.");
+
+	if (auto call = dynamic_cast<FunctionCall const*>(&_statement.expression()))
+	{
+		if (auto callType = dynamic_cast<FunctionType const*>(type(call->expression()).get()))
+		{
+			using Location = FunctionType::Location;
+			Location location = callType->location();
+			if (
+				location == Location::Bare ||
+				location == Location::BareCallCode ||
+				location == Location::BareDelegateCall ||
+				location == Location::Send
+			)
+				warning(_statement.location(), "Return value of low-level calls not used.");
+		}
+	}
 }
 
 bool TypeChecker::visit(Conditional const& _conditional)
@@ -1570,6 +1586,16 @@ void TypeChecker::typeError(SourceLocation const& _location, string const& _desc
 	m_errors.push_back(err);
 }
 
+void TypeChecker::warning(SourceLocation const& _location, string const& _description)
+{
+	auto err = make_shared<Error>(Error::Type::Warning);
+	*err <<
+		errinfo_sourceLocation(_location) <<
+		errinfo_comment(_description);
+
+	m_errors.push_back(err);
+}
+
 void TypeChecker::fatalTypeError(SourceLocation const& _location, string const& _description)
 {
 	typeError(_location, _description);
diff --git a/libsolidity/analysis/TypeChecker.h b/libsolidity/analysis/TypeChecker.h
index 48f8285a..be1e02be 100644
--- a/libsolidity/analysis/TypeChecker.h
+++ b/libsolidity/analysis/TypeChecker.h
@@ -59,6 +59,9 @@ private:
 	/// Adds a new error to the list of errors.
 	void typeError(SourceLocation const& _location, std::string const& _description);
 
+	/// Adds a new warning to the list of errors.
+	void warning(SourceLocation const& _location, std::string const& _description);
+
 	/// Adds a new error to the list of errors and throws to abort type checking.
 	void fatalTypeError(SourceLocation const& _location, std::string const& _description);
 
diff --git a/test/libsolidity/SolidityNameAndTypeResolution.cpp b/test/libsolidity/SolidityNameAndTypeResolution.cpp
index 697b3fa9..7e81bd7e 100644
--- a/test/libsolidity/SolidityNameAndTypeResolution.cpp
+++ b/test/libsolidity/SolidityNameAndTypeResolution.cpp
@@ -3750,6 +3750,79 @@ BOOST_AUTO_TEST_CASE(one_divided_by_three_integer_conversion)
 	BOOST_CHECK(!success(text));
 }
 
+BOOST_AUTO_TEST_CASE(unused_return_value)
+{
+	char const* text = R"(
+		contract test {
+			function g() returns (uint) {}
+			function f() {
+				g();
+			}
+		}
+	)";
+	BOOST_CHECK(success(text));
+}
+
+BOOST_AUTO_TEST_CASE(unused_return_value_send)
+{
+	char const* text = R"(
+		contract test {
+			function f() {
+				address(0x12).send(1);
+			}
+		}
+	)";
+	BOOST_CHECK(expectError(text, true) == Error::Type::Warning);
+}
+
+BOOST_AUTO_TEST_CASE(unused_return_value_call)
+{
+	char const* text = R"(
+		contract test {
+			function f() {
+				address(0x12).call("abc");
+			}
+		}
+	)";
+	BOOST_CHECK(expectError(text, true) == Error::Type::Warning);
+}
+
+BOOST_AUTO_TEST_CASE(unused_return_value_call_value)
+{
+	char const* text = R"(
+		contract test {
+			function f() {
+				address(0x12).call.value(2)("abc");
+			}
+		}
+	)";
+	BOOST_CHECK(expectError(text, true) == Error::Type::Warning);
+}
+
+BOOST_AUTO_TEST_CASE(unused_return_value_callcode)
+{
+	char const* text = R"(
+		contract test {
+			function f() {
+				address(0x12).callcode("abc");
+			}
+		}
+	)";
+	BOOST_CHECK(expectError(text, true) == Error::Type::Warning);
+}
+
+BOOST_AUTO_TEST_CASE(unused_return_value_delegatecall)
+{
+	char const* text = R"(
+		contract test {
+			function f() {
+				address(0x12).delegatecall("abc");
+			}
+		}
+	)";
+	BOOST_CHECK(expectError(text, true) == Error::Type::Warning);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }