6 files changed, 63 insertions, 10 deletions
diff --git a/libsolidity/analysis/ReferencesResolver.cpp b/libsolidity/analysis/ReferencesResolver.cpp
index 296a39c2..f91eaf6e 100644
--- a/libsolidity/analysis/ReferencesResolver.cpp
+++ b/libsolidity/analysis/ReferencesResolver.cpp
@@ -280,7 +280,8 @@ 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.
 	assembly::AsmAnalysisInfo analysisInfo;
-	assembly::AsmAnalyzer(analysisInfo, errorsIgnored, EVMVersion(), assembly::AsmFlavour::Loose, resolver).analyze(_inlineAssembly.operations());
+	boost::optional<Error::Type> errorTypeForLoose = m_experimental050Mode ? Error::Type::SyntaxError : Error::Type::Warning;
+	assembly::AsmAnalyzer(analysisInfo, errorsIgnored, EVMVersion(), errorTypeForLoose, assembly::AsmFlavour::Loose, resolver).analyze(_inlineAssembly.operations());
 	return false;
 }
 
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 1748b518..5d28e776 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -894,10 +894,15 @@ bool TypeChecker::visit(InlineAssembly const& _inlineAssembly)
 	};
 	solAssert(!_inlineAssembly.annotation().analysisInfo, "");
 	_inlineAssembly.annotation().analysisInfo = make_shared<assembly::AsmAnalysisInfo>();
+	boost::optional<Error::Type> errorTypeForLoose =
+		m_scope->sourceUnit().annotation().experimentalFeatures.count(ExperimentalFeature::V050) ?
+		Error::Type::SyntaxError :
+		Error::Type::Warning;
 	assembly::AsmAnalyzer analyzer(
 		*_inlineAssembly.annotation().analysisInfo,
 		m_errorReporter,
 		m_evmVersion,
+		errorTypeForLoose,
 		assembly::AsmFlavour::Loose,
 		identifierAccess
 	);
diff --git a/libsolidity/codegen/CompilerContext.cpp b/libsolidity/codegen/CompilerContext.cpp
index ebf0213a..0bf88267 100644
--- a/libsolidity/codegen/CompilerContext.cpp
+++ b/libsolidity/codegen/CompilerContext.cpp
@@ -330,6 +330,7 @@ void CompilerContext::appendInlineAssembly(
 			analysisInfo,
 			errorReporter,
 			m_evmVersion,
+			boost::none,
 			assembly::AsmFlavour::Strict,
 			identifierAccess.resolve
 		).analyze(*parserResult);
diff --git a/libsolidity/inlineasm/AsmAnalysis.cpp b/libsolidity/inlineasm/AsmAnalysis.cpp
index a7f764a5..abf7ddf2 100644
--- a/libsolidity/inlineasm/AsmAnalysis.cpp
+++ b/libsolidity/inlineasm/AsmAnalysis.cpp
@@ -54,7 +54,10 @@ bool AsmAnalyzer::analyze(Block const& _block)
 
 bool AsmAnalyzer::operator()(Label const& _label)
 {
-	solAssert(m_flavour == AsmFlavour::Loose, "");
+	checkLooseFeature(
+		_label.location,
+		"The use of labels is deprecated. Please use \"if\", \"switch\", \"for\" or function calls instead."
+	);
 	m_info.stackHeightInfo[&_label] = m_stackHeight;
 	warnOnInstructions(solidity::Instruction::JUMPDEST, _label.location);
 	return true;
@@ -62,7 +65,10 @@ bool AsmAnalyzer::operator()(Label const& _label)
 
 bool AsmAnalyzer::operator()(assembly::Instruction const& _instruction)
 {
-	solAssert(m_flavour == AsmFlavour::Loose, "");
+	checkLooseFeature(
+		_instruction.location,
+		"The use of non-functional instructions is deprecated. Please use functional notation instead."
+	);
 	auto const& info = instructionInfo(_instruction.instruction);
 	m_stackHeight += info.ret - info.args;
 	m_info.stackHeightInfo[&_instruction] = m_stackHeight;
@@ -170,18 +176,31 @@ bool AsmAnalyzer::operator()(FunctionalInstruction const& _instr)
 
 bool AsmAnalyzer::operator()(assembly::ExpressionStatement const& _statement)
 {
-	size_t initialStackHeight = m_stackHeight;
+	int initialStackHeight = m_stackHeight;
 	bool success = boost::apply_visitor(*this, _statement.expression);
-	if (m_flavour != AsmFlavour::Loose)
-		if (!expectDeposit(0, initialStackHeight, _statement.location))
+	if (m_stackHeight != initialStackHeight && (m_flavour != AsmFlavour::Loose || m_errorTypeForLoose))
+	{
+		Error::Type errorType = m_flavour == AsmFlavour::Loose ? *m_errorTypeForLoose : Error::Type::TypeError;
+		string msg =
+			"Top-level expressions are not supposed to return values (this expression returns " +
+			boost::lexical_cast<string>(m_stackHeight - initialStackHeight) +
+			" value" +
+			(m_stackHeight - initialStackHeight == 1 ? "" : "s") +
+			"). Use ``pop()`` or assign them.";
+		m_errorReporter.error(errorType, _statement.location, msg);
+		if (errorType != Error::Type::Warning)
 			success = false;
+	}
 	m_info.stackHeightInfo[&_statement] = m_stackHeight;
 	return success;
 }
 
 bool AsmAnalyzer::operator()(assembly::StackAssignment const& _assignment)
 {
-	solAssert(m_flavour == AsmFlavour::Loose, "");
+	checkLooseFeature(
+		_assignment.location,
+		"The use of stack assignment is deprecated. Please use assignment in functional notation instead."
+	);
 	bool success = checkAssignment(_assignment.variableName, size_t(-1));
 	m_info.stackHeightInfo[&_assignment] = m_stackHeight;
 	return success;
@@ -577,10 +596,22 @@ void AsmAnalyzer::warnOnInstructions(solidity::Instruction _instr, SourceLocatio
 		);
 
 	if (_instr == solidity::Instruction::JUMP || _instr == solidity::Instruction::JUMPI || _instr == solidity::Instruction::JUMPDEST)
-		m_errorReporter.warning(
+	{
+		solAssert(m_flavour == AsmFlavour::Loose, "");
+		m_errorReporter.error(
+			m_errorTypeForLoose ? *m_errorTypeForLoose : Error::Type::Warning,
 			_location,
 			"Jump instructions and labels are low-level EVM features that can lead to "
 			"incorrect stack access. Because of that they are discouraged. "
 			"Please consider using \"switch\", \"if\" or \"for\" statements instead."
 		);
+	}
+}
+
+void AsmAnalyzer::checkLooseFeature(SourceLocation const& _location, string const& _description)
+{
+	if (m_flavour != AsmFlavour::Loose)
+		solAssert(false, _description);
+	else if (m_errorTypeForLoose)
+		m_errorReporter.error(*m_errorTypeForLoose, _location, _description);
 }
diff --git a/libsolidity/inlineasm/AsmAnalysis.h b/libsolidity/inlineasm/AsmAnalysis.h
index 867711c7..8d2a71f0 100644
--- a/libsolidity/inlineasm/AsmAnalysis.h
+++ b/libsolidity/inlineasm/AsmAnalysis.h
@@ -30,6 +30,7 @@
 #include <libsolidity/inlineasm/AsmDataForward.h>
 
 #include <boost/variant.hpp>
+#include <boost/optional.hpp>
 
 #include <functional>
 #include <memory>
@@ -56,9 +57,17 @@ public:
 		AsmAnalysisInfo& _analysisInfo,
 		ErrorReporter& _errorReporter,
 		EVMVersion _evmVersion,
+		boost::optional<Error::Type> _errorTypeForLoose,
 		AsmFlavour _flavour = AsmFlavour::Loose,
 		julia::ExternalIdentifierAccess::Resolver const& _resolver = julia::ExternalIdentifierAccess::Resolver()
-	): m_resolver(_resolver), m_info(_analysisInfo), m_errorReporter(_errorReporter), m_evmVersion(_evmVersion), m_flavour(_flavour) {}
+	):
+		m_resolver(_resolver),
+		m_info(_analysisInfo),
+		m_errorReporter(_errorReporter),
+		m_evmVersion(_evmVersion),
+		m_flavour(_flavour),
+		m_errorTypeForLoose(_errorTypeForLoose)
+	{}
 
 	bool analyze(assembly::Block const& _block);
 
@@ -91,6 +100,11 @@ private:
 	void expectValidType(std::string const& type, SourceLocation const& _location);
 	void warnOnInstructions(solidity::Instruction _instr, SourceLocation const& _location);
 
+	/// Depending on @a m_flavour and @a m_errorTypeForLoose, throws an internal compiler
+	/// exception (if the flavour is not Loose), reports an error/warning
+	/// (if m_errorTypeForLoose is set) or does nothing.
+	void checkLooseFeature(SourceLocation const& _location, std::string const& _description);
+
 	int m_stackHeight = 0;
 	julia::ExternalIdentifierAccess::Resolver m_resolver;
 	Scope* m_currentScope = nullptr;
@@ -101,6 +115,7 @@ private:
 	ErrorReporter& m_errorReporter;
 	EVMVersion m_evmVersion;
 	AsmFlavour m_flavour = AsmFlavour::Loose;
+	boost::optional<Error::Type> m_errorTypeForLoose;
 };
 
 }
diff --git a/libsolidity/interface/AssemblyStack.cpp b/libsolidity/interface/AssemblyStack.cpp
index 7a9fffbf..7f97336b 100644
--- a/libsolidity/interface/AssemblyStack.cpp
+++ b/libsolidity/interface/AssemblyStack.cpp
@@ -91,7 +91,7 @@ bool AssemblyStack::analyze(assembly::Block const& _block, Scanner const* _scann
 bool AssemblyStack::analyzeParsed()
 {
 	m_analysisInfo = make_shared<assembly::AsmAnalysisInfo>();
-	assembly::AsmAnalyzer analyzer(*m_analysisInfo, m_errorReporter, m_evmVersion, languageToAsmFlavour(m_language));
+	assembly::AsmAnalyzer analyzer(*m_analysisInfo, m_errorReporter, m_evmVersion, boost::none, languageToAsmFlavour(m_language));
 	m_analysisSuccessful = analyzer.analyze(*m_parserResult);
 	return m_analysisSuccessful;
 }