Merge pull request #7551 from ethereum/060-cxx17-std-optional

Use `std::optional<>` rather than `boost::optional<>`

libsolidity/analysis/ReferencesResolver.cpp

@@ -122,7 +122,7 @@ bool ReferencesResolver::visit(ElementaryTypeName const& _typeName)
 	if (!_typeName.annotation().type)
 	{
 		_typeName.annotation().type = TypeProvider::fromElementaryTypeName(_typeName.typeName());
-		if (_typeName.stateMutability().is_initialized())
+		if (_typeName.stateMutability().has_value())
 		{
 			// for non-address types this was already caught by the parser
 			solAssert(_typeName.annotation().type->category() == Type::Category::Address, "");
@@ -323,7 +323,7 @@ bool ReferencesResolver::visit(InlineAssembly const& _inlineAssembly)
 	// Will be re-generated later with correct information
 	// We use the latest EVM version because we will re-run it anyway.
 	yul::AsmAnalysisInfo analysisInfo;
-	boost::optional<Error::Type> errorTypeForLoose = Error::Type::SyntaxError;
+	std::optional<Error::Type> errorTypeForLoose = Error::Type::SyntaxError;
 	yul::AsmAnalyzer(
 		analysisInfo,
 		errorsIgnored,

libsolidity/analysis/ViewPureChecker.cpp

@@ -241,7 +241,7 @@ void ViewPureChecker::endVisit(InlineAssembly const& _inlineAssembly)
 void ViewPureChecker::reportMutability(
 	StateMutability _mutability,
 	SourceLocation const& _location,
-	boost::optional<SourceLocation> const& _nestedLocation
+	std::optional<SourceLocation> const& _nestedLocation
 )
 {
 	if (_mutability > m_bestMutabilityAndLocation.mutability)

libsolidity/analysis/ViewPureChecker.h

@@ -23,6 +23,7 @@
 
 #include <map>
 #include <memory>
+#include <optional>
 
 namespace langutil
 {
@@ -67,7 +68,7 @@ private:
 	void reportMutability(
 		StateMutability _mutability,
 		langutil::SourceLocation const& _location,
-		boost::optional<langutil::SourceLocation> const& _nestedLocation = {}
+		std::optional<langutil::SourceLocation> const& _nestedLocation = {}
 	);
 
 	std::vector<std::shared_ptr<ASTNode>> const& m_ast;