From 25a64c7f8f35833b9dec6068232be6e0ce9d2e78 Mon Sep 17 00:00:00 2001
From: chriseth <c@ethdev.com>
Date: Fri, 24 Jun 2016 16:41:17 +0200
Subject: [PATCH] Only warn about unused return in low-level functions.

---
 libsolidity/analysis/TypeChecker.cpp          | 21 +++++---
 .../SolidityNameAndTypeResolution.cpp         | 50 ++++++++++++++++++-
 2 files changed, 64 insertions(+), 7 deletions(-)

diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index c2fd3e7eeb47..6b2c1cb8ee9f 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -831,12 +831,21 @@ void TypeChecker::endVisit(ExpressionStatement const& _statement)
 		if (!dynamic_cast<RationalNumberType const&>(*type(_statement.expression())).mobileType())
 			typeError(_statement.expression().location(), "Invalid rational number.");
 
-	bool unusedReturnValue = true;
-	if (auto t = dynamic_cast<TupleType const*>(type(_statement.expression()).get()))
-		if (t->components().empty())
-			unusedReturnValue = false;
-	if (unusedReturnValue)
-		warning(_statement.location(), "Unused return value.");
+	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)
diff --git a/test/libsolidity/SolidityNameAndTypeResolution.cpp b/test/libsolidity/SolidityNameAndTypeResolution.cpp
index 1f42c23ed29e..7e81bd7ec720 100644
--- a/test/libsolidity/SolidityNameAndTypeResolution.cpp
+++ b/test/libsolidity/SolidityNameAndTypeResolution.cpp
@@ -3760,7 +3760,7 @@ BOOST_AUTO_TEST_CASE(unused_return_value)
 			}
 		}
 	)";
-	BOOST_CHECK(expectError(text, true) == Error::Type::Warning);
+	BOOST_CHECK(success(text));
 }
 
 BOOST_AUTO_TEST_CASE(unused_return_value_send)
@@ -3775,6 +3775,54 @@ BOOST_AUTO_TEST_CASE(unused_return_value_send)
 	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()
 
 }