Warn about side-effect free statements.

3 files changed, 11 insertions, 2 deletions

diff --git a/libsolidity/analysis/StaticAnalyzer.cpp b/libsolidity/analysis/StaticAnalyzer.cpp
index c39f874e..df7f6e88 100644
--- a/libsolidity/analysis/StaticAnalyzer.cpp
+++ b/libsolidity/analysis/StaticAnalyzer.cpp
@@ -57,6 +57,13 @@ void StaticAnalyzer::endVisit(FunctionDefinition const&)
 	m_nonPayablePublic = false;
 }
 
+bool StaticAnalyzer::visit(ExpressionStatement const& _statement)
+{
+	if (_statement.expression().annotation().isPure)
+		warning(_statement.location(), "Statement has no effects.");
+	return true;
+}
+
 bool StaticAnalyzer::visit(MemberAccess const& _memberAccess)
 {
 	if (m_nonPayablePublic && !m_library)
diff --git a/libsolidity/analysis/StaticAnalyzer.h b/libsolidity/analysis/StaticAnalyzer.h
index 0cb961bd..84342322 100644
--- a/libsolidity/analysis/StaticAnalyzer.h
+++ b/libsolidity/analysis/StaticAnalyzer.h
@@ -60,6 +60,8 @@ private:
 	virtual bool visit(FunctionDefinition const& _function) override;
 	virtual void endVisit(FunctionDefinition const& _function) override;
 
+	virtual bool visit(ExpressionStatement const& _statement) override;
+
 	virtual bool visit(MemberAccess const& _memberAccess) override;
 
 	ErrorList& m_errors;
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index dc04404d..b37db7b7 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -1674,8 +1674,8 @@ bool TypeChecker::visit(Identifier const& _identifier)
 	if (auto variableDeclaration = dynamic_cast<VariableDeclaration const*>(annotation.referencedDeclaration))
 		annotation.isPure = annotation.isConstant = variableDeclaration->isConstant();
 	else if (dynamic_cast<MagicVariableDeclaration const*>(annotation.referencedDeclaration))
-		if (auto functionType = dynamic_cast<FunctionType const*>(annotation.type.get()))
-			annotation.isPure = functionType->isPure();
+		if (dynamic_cast<FunctionType const*>(annotation.type.get()))
+			annotation.isPure = true;
 	return false;
 }