Update Dockerfiles and CI scripts to Ubuntu 20.04 and simplify them.

libyul/AsmAnalysis.cpp

@@ -527,7 +527,7 @@ bool AsmAnalyzer::warnOnInstructions(evmasm::Instruction _instr, SourceLocation
 	// Similarly we assume bitwise shifting and create2 go together.
 	yulAssert(m_evmVersion.hasBitwiseShifting() == m_evmVersion.hasCreate2(), "");
 
-	auto errorForVM = [=](string const& vmKindMessage) {
+	auto errorForVM = [&](string const& vmKindMessage) {
 		typeError(
 			_location,
 			"The \"" +

libyul/backends/evm/EVMCodeTransform.cpp

@@ -85,11 +85,11 @@ void VariableReferenceCounter::operator()(Block const& _block)
 void VariableReferenceCounter::increaseRefIfFound(YulString _variableName)
 {
 	m_scope->lookup(_variableName, GenericVisitor{
-		[=](Scope::Variable const& _var)
+		[&](Scope::Variable const& _var)
 		{
 			++m_context.variableReferences[&_var];
 		},
-		[=](Scope::Function const&) { }
+		[](Scope::Function const&) { }
 	});
 }
 
@@ -272,7 +272,7 @@ void CodeTransform::operator()(FunctionCall const& _call)
 
 		Scope::Function* function = nullptr;
 		yulAssert(m_scope->lookup(_call.functionName.name, GenericVisitor{
-			[=](Scope::Variable&) { yulAssert(false, "Expected function name."); },
+			[](Scope::Variable&) { yulAssert(false, "Expected function name."); },
 			[&](Scope::Function& _function) { function = &_function; }
 		}), "Function name not found.");
 		yulAssert(function, "");
@@ -296,7 +296,7 @@ void CodeTransform::operator()(Identifier const& _identifier)
 	// First search internals, then externals.
 	yulAssert(m_scope, "");
 	if (m_scope->lookup(_identifier.name, GenericVisitor{
-		[=](Scope::Variable& _var)
+		[&](Scope::Variable& _var)
 		{
 			// TODO: opportunity for optimization: Do not DUP if this is the last reference
 			// to the top most element of the stack
@@ -307,7 +307,7 @@ void CodeTransform::operator()(Identifier const& _identifier)
 				m_assembly.appendConstant(u256(0));
 			decreaseReference(_identifier.name, _var);
 		},
-		[=](Scope::Function&)
+		[](Scope::Function&)
 		{
 			yulAssert(false, "Function not removed during desugaring.");
 		}

libyul/backends/wasm/EVMToEwasmTranslator.cpp

@@ -1232,7 +1232,7 @@ Object EVMToEwasmTranslator::run(Object const& _object)
 
 	FunctionHoister::run(context, ast);
 	FunctionGrouper::run(context, ast);
-	MainFunction{}(ast);
+	MainFunction::run(context, ast);
 	ForLoopConditionIntoBody::run(context, ast);
 	ExpressionSplitter::run(context, ast);
 	WordSizeTransform::run(m_dialect, WasmDialect::instance(), ast, nameDispenser);

libyul/optimiser/RedundantAssignEliminator.cpp

@@ -306,7 +306,7 @@ void RedundantAssignEliminator::finalize(YulString _variable, RedundantAssignEli
 
 void AssignmentRemover::operator()(Block& _block)
 {
-	boost::range::remove_erase_if(_block.statements, [=](Statement const& _statement) -> bool {
+	boost::range::remove_erase_if(_block.statements, [&](Statement const& _statement) -> bool {
 		return holds_alternative<Assignment>(_statement) && m_toRemove.count(&std::get<Assignment>(_statement));
 	});
 

libyul/optimiser/UnusedPruner.cpp

@@ -86,7 +86,7 @@ void UnusedPruner::operator()(Block& _block)
 			if (std::none_of(
 				varDecl.variables.begin(),
 				varDecl.variables.end(),
-				[=](TypedName const& _typedName) { return used(_typedName.name); }
+				[&](TypedName const& _typedName) { return used(_typedName.name); }
 			))
 			{
 				if (!varDecl.value)