Merge pull request #304 from chriseth/imp

Simple aliasing during import

13 files changed, 240 insertions, 58 deletions

diff --git a/libsolidity/analysis/NameAndTypeResolver.cpp b/libsolidity/analysis/NameAndTypeResolver.cpp
index efdb1953..92347bfc 100644
--- a/libsolidity/analysis/NameAndTypeResolver.cpp
+++ b/libsolidity/analysis/NameAndTypeResolver.cpp
@@ -46,14 +46,16 @@ NameAndTypeResolver::NameAndTypeResolver(
 
 bool NameAndTypeResolver::registerDeclarations(SourceUnit& _sourceUnit)
 {
-	solAssert(!m_scopes[&_sourceUnit], "");
-	m_scopes[&_sourceUnit].reset(new DeclarationContainer(nullptr, m_scopes[nullptr].get()));
+	if (!m_scopes[&_sourceUnit])
+		// By importing, it is possible that the container already exists.
+		m_scopes[&_sourceUnit].reset(new DeclarationContainer(nullptr, m_scopes[nullptr].get()));
 	m_currentScope = m_scopes[&_sourceUnit].get();
 
 	// The helper registers all declarations in m_scopes as a side-effect of its construction.
 	try
 	{
 		DeclarationRegistrationHelper registrar(m_scopes, _sourceUnit, m_errors);
+		_sourceUnit.annotation().exportedSymbols = m_scopes[&_sourceUnit]->declarations();
 	}
 	catch (FatalError const&)
 	{
@@ -78,12 +80,12 @@ bool NameAndTypeResolver::performImports(SourceUnit& _sourceUnit, map<string, So
 					"Import \"" +
 					path +
 					"\" (referenced as \"" +
-					imp->identifier() +
+					imp->path() +
 					"\") not found."
 				);
 				error = true;
 			}
-			else
+			else if (imp->name().empty())
 			{
 				auto scope = m_scopes.find(_sourceUnits.at(path));
 				solAssert(scope != end(m_scopes), "");
@@ -380,7 +382,7 @@ void NameAndTypeResolver::reportFatalTypeError(Error const& _e)
 }
 
 DeclarationRegistrationHelper::DeclarationRegistrationHelper(
-	map<ASTNode const*, unique_ptr<DeclarationContainer>>& _scopes,
+	map<ASTNode const*, shared_ptr<DeclarationContainer>>& _scopes,
 	ASTNode& _astRoot,
 	ErrorList& _errors
 ):
@@ -392,6 +394,17 @@ DeclarationRegistrationHelper::DeclarationRegistrationHelper(
 	_astRoot.accept(*this);
 }
 
+bool DeclarationRegistrationHelper::visit(ImportDirective& _import)
+{
+	SourceUnit const* importee = _import.annotation().sourceUnit;
+	solAssert(!!importee, "");
+	if (!m_scopes[importee])
+		m_scopes[importee].reset(new DeclarationContainer(nullptr, m_scopes[nullptr].get()));
+	m_scopes[&_import] = m_scopes[importee];
+	registerDeclaration(_import, false);
+	return true;
+}
+
 bool DeclarationRegistrationHelper::visit(ContractDefinition& _contract)
 {
 	registerDeclaration(_contract, true);
@@ -489,9 +502,9 @@ void DeclarationRegistrationHelper::endVisit(EventDefinition&)
 
 void DeclarationRegistrationHelper::enterNewSubScope(Declaration const& _declaration)
 {
-	map<ASTNode const*, unique_ptr<DeclarationContainer>>::iterator iter;
+	map<ASTNode const*, shared_ptr<DeclarationContainer>>::iterator iter;
 	bool newlyAdded;
-	unique_ptr<DeclarationContainer> container(new DeclarationContainer(m_currentScope, m_scopes[m_currentScope].get()));
+	shared_ptr<DeclarationContainer> container(new DeclarationContainer(m_currentScope, m_scopes[m_currentScope].get()));
 	tie(iter, newlyAdded) = m_scopes.emplace(&_declaration, move(container));
 	solAssert(newlyAdded, "Unable to add new scope.");
 	m_currentScope = &_declaration;
diff --git a/libsolidity/analysis/NameAndTypeResolver.h b/libsolidity/analysis/NameAndTypeResolver.h
index 3c444aba..89b9818b 100644
--- a/libsolidity/analysis/NameAndTypeResolver.h
+++ b/libsolidity/analysis/NameAndTypeResolver.h
@@ -111,7 +111,8 @@ private:
 	/// Maps nodes declaring a scope to scopes, i.e. ContractDefinition and FunctionDeclaration,
 	/// where nullptr denotes the global scope. Note that structs are not scope since they do
 	/// not contain code.
-	std::map<ASTNode const*, std::unique_ptr<DeclarationContainer>> m_scopes;
+	/// Aliases (for example `import "x" as y;`) create multiple pointers to the same scope.
+	std::map<ASTNode const*, std::shared_ptr<DeclarationContainer>> m_scopes;
 
 	DeclarationContainer* m_currentScope = nullptr;
 	ErrorList& m_errors;
@@ -125,12 +126,13 @@ class DeclarationRegistrationHelper: private ASTVisitor
 {
 public:
 	DeclarationRegistrationHelper(
-		std::map<ASTNode const*, std::unique_ptr<DeclarationContainer>>& _scopes,
+		std::map<ASTNode const*, std::shared_ptr<DeclarationContainer>>& _scopes,
 		ASTNode& _astRoot,
 		ErrorList& _errors
 	);
 
 private:
+	bool visit(ImportDirective& _declaration) override;
 	bool visit(ContractDefinition& _contract) override;
 	void endVisit(ContractDefinition& _contract) override;
 	bool visit(StructDefinition& _struct) override;
@@ -166,7 +168,7 @@ private:
 	// creates the Declaration error and adds it in the errors list and throws FatalError
 	void fatalDeclarationError(SourceLocation _sourceLocation, std::string const& _description);
 
-	std::map<ASTNode const*, std::unique_ptr<DeclarationContainer>>& m_scopes;
+	std::map<ASTNode const*, std::shared_ptr<DeclarationContainer>>& m_scopes;
 	ASTNode const* m_currentScope = nullptr;
 	VariableScope* m_currentFunction = nullptr;
 	ErrorList& m_errors;
diff --git a/libsolidity/ast/AST.cpp b/libsolidity/ast/AST.cpp
index 701202f9..b5affa8e 100644
--- a/libsolidity/ast/AST.cpp
+++ b/libsolidity/ast/AST.cpp
@@ -56,6 +56,13 @@ Error ASTNode::createTypeError(string const& _description) const
 	return Error(Error::Type::TypeError) << errinfo_sourceLocation(location()) << errinfo_comment(_description);
 }
 
+SourceUnitAnnotation& SourceUnit::annotation() const
+{
+	if (!m_annotation)
+		m_annotation = new SourceUnitAnnotation();
+	return static_cast<SourceUnitAnnotation&>(*m_annotation);
+}
+
 ImportAnnotation& ImportDirective::annotation() const
 {
 	if (!m_annotation)
@@ -63,6 +70,12 @@ ImportAnnotation& ImportDirective::annotation() const
 	return static_cast<ImportAnnotation&>(*m_annotation);
 }
 
+TypePointer ImportDirective::type() const
+{
+	solAssert(!!annotation().sourceUnit, "");
+	return make_shared<ModuleType>(*annotation().sourceUnit);
+}
+
 map<FixedHash<4>, FunctionTypePointer> ContractDefinition::interfaceFunctions() const
 {
 	auto exportedFunctionList = interfaceFunctionList();
diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
index 1ba4f65b..84e9e706 100644
--- a/libsolidity/ast/AST.h
+++ b/libsolidity/ast/AST.h
@@ -120,6 +120,7 @@ public:
 
 	virtual void accept(ASTVisitor& _visitor) override;
 	virtual void accept(ASTConstVisitor& _visitor) const override;
+	virtual SourceUnitAnnotation& annotation() const override;
 
 	std::vector<ASTPointer<ASTNode>> nodes() const { return m_nodes; }
 
@@ -128,28 +129,7 @@ private:
 };
 
 /**
- * Import directive for referencing other files / source objects.
- * Example: import "abc.sol"
- * Source objects are identified by a string which can be a file name but does not have to be.
- */
-class ImportDirective: public ASTNode
-{
-public:
-	ImportDirective(SourceLocation const& _location, ASTPointer<ASTString> const& _identifier):
-		ASTNode(_location), m_identifier(_identifier) {}
-
-	virtual void accept(ASTVisitor& _visitor) override;
-	virtual void accept(ASTConstVisitor& _visitor) const override;
-
-	ASTString const& identifier() const { return *m_identifier; }
-	virtual ImportAnnotation& annotation() const override;
-
-private:
-	ASTPointer<ASTString> m_identifier;
-};
-
-/**
- * Abstract AST class for a declaration (contract, function, struct, variable).
+ * Abstract AST class for a declaration (contract, function, struct, variable, import directive).
  */
 class Declaration: public ASTNode
 {
@@ -195,6 +175,45 @@ private:
 };
 
 /**
+ * Import directive for referencing other files / source objects.
+ * Example: import "abc.sol" // imports all symbols of "abc.sol" into current scope
+ * Source objects are identified by a string which can be a file name but does not have to be.
+ * Other ways to use it:
+ * import "abc" as x; // creates symbol "x" that contains all symbols in "abc"
+ * import * as x from "abc"; // same as above
+ * import {a as b, c} from "abc"; // creates new symbols "b" and "c" referencing "a" and "c" in "abc", respectively.
+ */
+class ImportDirective: public Declaration
+{
+public:
+	ImportDirective(
+		SourceLocation const& _location,
+		ASTPointer<ASTString> const& _path,
+		ASTPointer<ASTString> const& _unitAlias,
+		std::vector<std::pair<ASTPointer<Identifier>, ASTPointer<ASTString>>>&& _symbolAliases
+	):
+		Declaration(_location, _unitAlias),
+		m_path(_path),
+		m_symbolAliases(_symbolAliases)
+	{ }
+
+	virtual void accept(ASTVisitor& _visitor) override;
+	virtual void accept(ASTConstVisitor& _visitor) const override;
+
+	ASTString const& path() const { return *m_path; }
+	virtual ImportAnnotation& annotation() const override;
+
+	virtual TypePointer type() const override;
+
+private:
+	ASTPointer<ASTString> m_path;
+	/// The aliases for the specific symbols to import. If non-empty import the specific symbols.
+	/// If the second component is empty, import the identifier unchanged.
+	/// If both m_unitAlias and m_symbolAlias are empty, import all symbols into the current scope.
+	std::vector<std::pair<ASTPointer<Identifier>, ASTPointer<ASTString>>> m_symbolAliases;
+};
+
+/**
  * Abstract class that is added to each AST node that can store local variables.
  */
 class VariableScope
diff --git a/libsolidity/ast/ASTAnnotations.h b/libsolidity/ast/ASTAnnotations.h
index 0bc91c60..235338bb 100644
--- a/libsolidity/ast/ASTAnnotations.h
+++ b/libsolidity/ast/ASTAnnotations.h
@@ -54,10 +54,20 @@ struct DocumentedAnnotation
 	std::multimap<std::string, DocTag> docTags;
 };
 
+struct SourceUnitAnnotation: ASTAnnotation
+{
+	/// The "absolute" (in the compiler sense) path of this source unit.
+	std::string path;
+	/// The exported symbols (all global symbols).
+	std::map<ASTString, std::vector<Declaration const*>> exportedSymbols;
+};
+
 struct ImportAnnotation: ASTAnnotation
 {
 	/// The absolute path of the source unit to import.
 	std::string absolutePath;
+	/// The actual source unit.
+	SourceUnit const* sourceUnit = nullptr;
 };
 
 struct TypeDeclarationAnnotation: ASTAnnotation
diff --git a/libsolidity/ast/ASTJsonConverter.cpp b/libsolidity/ast/ASTJsonConverter.cpp
index f208c3c9..377fa7e6 100644
--- a/libsolidity/ast/ASTJsonConverter.cpp
+++ b/libsolidity/ast/ASTJsonConverter.cpp
@@ -91,7 +91,7 @@ Json::Value const& ASTJsonConverter::json()
 
 bool ASTJsonConverter::visit(ImportDirective const& _node)
 {
-	addJsonNode("Import", { make_pair("file", _node.identifier())});
+	addJsonNode("Import", { make_pair("file", _node.path())});
 	return true;
 }
 
diff --git a/libsolidity/ast/ASTPrinter.cpp b/libsolidity/ast/ASTPrinter.cpp
index 9253e0bf..b2ce1c26 100644
--- a/libsolidity/ast/ASTPrinter.cpp
+++ b/libsolidity/ast/ASTPrinter.cpp
@@ -49,7 +49,7 @@ void ASTPrinter::print(ostream& _stream)
 
 bool ASTPrinter::visit(ImportDirective const& _node)
 {
-	writeLine("ImportDirective \"" + _node.identifier() + "\"");
+	writeLine("ImportDirective \"" + _node.path() + "\"");
 	printSourcePart(_node);
 	return goDeeper();
 }
diff --git a/libsolidity/ast/Types.cpp b/libsolidity/ast/Types.cpp
index 2dc7fb84..49347022 100644
--- a/libsolidity/ast/Types.cpp
+++ b/libsolidity/ast/Types.cpp
@@ -1925,9 +1925,25 @@ string ModifierType::toString(bool _short) const
 	return name + ")";
 }
 
-MagicType::MagicType(MagicType::Kind _kind):
-	m_kind(_kind)
+bool ModuleType::operator==(Type const& _other) const
 {
+	if (_other.category() != category())
+		return false;
+	return &m_sourceUnit == &dynamic_cast<ModuleType const&>(_other).m_sourceUnit;
+}
+
+MemberList::MemberMap ModuleType::nativeMembers(ContractDefinition const*) const
+{
+	MemberList::MemberMap symbols;
+	for (auto const& symbolName: m_sourceUnit.annotation().exportedSymbols)
+		for (Declaration const* symbol: symbolName.second)
+			symbols.push_back(MemberList::Member(symbolName.first, symbol->type(), symbol));
+	return symbols;
+}
+
+string ModuleType::toString(bool) const
+{
+	return string("module \"") + m_sourceUnit.annotation().path + string("\"");
 }
 
 bool MagicType::operator==(Type const& _other) const
diff --git a/libsolidity/ast/Types.h b/libsolidity/ast/Types.h
index 3ebcb2b2..723d633b 100644
--- a/libsolidity/ast/Types.h
+++ b/libsolidity/ast/Types.h
@@ -134,7 +134,7 @@ public:
 	{
 		Integer, IntegerConstant, StringLiteral, Bool, Real, Array,
 		FixedBytes, Contract, Struct, Function, Enum, Tuple,
-		Mapping, TypeType, Modifier, Magic
+		Mapping, TypeType, Modifier, Magic, Module
 	};
 
 	/// @{
@@ -969,6 +969,34 @@ private:
 };
 
 
+
+/**
+ * Special type for imported modules. These mainly give access to their scope via members.
+ */
+class ModuleType: public Type
+{
+public:
+	virtual Category category() const override { return Category::Module; }
+
+	explicit ModuleType(SourceUnit const& _source): m_sourceUnit(_source) {}
+
+	virtual TypePointer binaryOperatorResult(Token::Value, TypePointer const&) const override
+	{
+		return TypePointer();
+	}
+
+	virtual bool operator==(Type const& _other) const override;
+	virtual bool canBeStored() const override { return false; }
+	virtual bool canLiveOutsideStorage() const override { return true; }
+	virtual unsigned sizeOnStack() const override { return 0; }
+	virtual MemberList::MemberMap nativeMembers(ContractDefinition const*) const override;
+
+	virtual std::string toString(bool _short) const override;
+
+private:
+	SourceUnit const& m_sourceUnit;
+};
+
 /**
  * Special type for magic variables (block, msg, tx), similar to a struct but without any reference
  * (it always references a global singleton by name).
@@ -979,7 +1007,7 @@ public:
 	enum class Kind { Block, Message, Transaction };
 	virtual Category category() const override { return Category::Magic; }
 
-	explicit MagicType(Kind _kind);
+	explicit MagicType(Kind _kind): m_kind(_kind) {}
 
 	virtual TypePointer binaryOperatorResult(Token::Value, TypePointer const&) const override
 	{
diff --git a/libsolidity/interface/CompilerStack.cpp b/libsolidity/interface/CompilerStack.cpp
index 7f097523..a6f6f224 100644
--- a/libsolidity/interface/CompilerStack.cpp
+++ b/libsolidity/interface/CompilerStack.cpp
@@ -111,6 +111,8 @@ bool CompilerStack::parse()
 		sourcePair.second.ast = Parser(m_errors).parse(sourcePair.second.scanner);
 		if (!sourcePair.second.ast)
 			solAssert(!Error::containsOnlyWarnings(m_errors), "Parser returned null but did not report error.");
+		else
+			sourcePair.second.ast->annotation().path = sourcePair.first;
 		sourceUnitsByName[sourcePair.first] = sourcePair.second.ast.get();
 	}
 	if (!Error::containsOnlyWarnings(m_errors))
@@ -376,7 +378,7 @@ void CompilerStack::resolveImports()
 		for (ASTPointer<ASTNode> const& node: _source->ast->nodes())
 			if (ImportDirective const* import = dynamic_cast<ImportDirective*>(node.get()))
 			{
-				string path = absolutePath(import->identifier(), _sourceName);
+				string path = absolutePath(import->path(), _sourceName);
 				import->annotation().absolutePath = path;
 				if (!m_sources.count(path))
 					BOOST_THROW_EXCEPTION(
@@ -384,6 +386,7 @@ void CompilerStack::resolveImports()
 							<< errinfo_sourceLocation(import->location())
 							<< errinfo_comment("Source not found.")
 					);
+				import->annotation().sourceUnit = m_sources.at(path).ast.get();
 
 				toposort(path, &m_sources[path]);
 			}
diff --git a/libsolidity/parsing/Parser.cpp b/libsolidity/parsing/Parser.cpp
index caf38b1d..2b31c385 100644
--- a/libsolidity/parsing/Parser.cpp
+++ b/libsolidity/parsing/Parser.cpp
@@ -83,7 +83,7 @@ ASTPointer<SourceUnit> Parser::parse(shared_ptr<Scanner> const& _scanner)
 				nodes.push_back(parseContractDefinition(token == Token::Library));
 				break;
 			default:
-				fatalParserError(std::string("Expected import directive or contract definition."));
+				fatalParserError(string("Expected import directive or contract definition."));
 			}
 		}
 		return nodeFactory.createNode<SourceUnit>(nodes);
@@ -113,14 +113,65 @@ int Parser::endPosition() const
 
 ASTPointer<ImportDirective> Parser::parseImportDirective()
 {
+	// import "abc" [as x];
+	// import * as x from "abc";
+	// import {a as b, c} from "abc";
 	ASTNodeFactory nodeFactory(*this);
 	expectToken(Token::Import);
-	if (m_scanner->currentToken() != Token::StringLiteral)
-		fatalParserError(std::string("Expected string literal (URL)."));
-	ASTPointer<ASTString> url = getLiteralAndAdvance();
+	ASTPointer<ASTString> path;
+	ASTPointer<ASTString> unitAlias = make_shared<string>();
+	vector<pair<ASTPointer<Identifier>, ASTPointer<ASTString>>> symbolAliases;
+
+	if (m_scanner->currentToken() == Token::StringLiteral)
+	{
+		path = getLiteralAndAdvance();
+		if (m_scanner->currentToken() == Token::As)
+		{
+			m_scanner->next();
+			unitAlias = expectIdentifierToken();
+		}
+	}
+	else
+	{
+		if (m_scanner->currentToken() == Token::LBrace)
+		{
+			m_scanner->next();
+			while (true)
+			{
+				ASTPointer<Identifier> id = parseIdentifier();
+				ASTPointer<ASTString> alias;
+				if (m_scanner->currentToken() == Token::As)
+				{
+					expectToken(Token::As);
+					alias = expectIdentifierToken();
+				}
+				symbolAliases.push_back(move(make_pair(move(id), move(alias))));
+				if (m_scanner->currentToken() != Token::Comma)
+					break;
+				m_scanner->next();
+			}
+			expectToken(Token::RBrace);
+		}
+		else if (m_scanner->currentToken() == Token::Mul)
+		{
+			m_scanner->next();
+			expectToken(Token::As);
+			unitAlias = expectIdentifierToken();
+		}
+		else
+			fatalParserError("Expected string literal (path), \"*\" or alias list.");
+		// "from" is not a keyword but parsed as an identifier because of backwards
+		// compatibility and because it is a really common word.
+		if (m_scanner->currentToken() != Token::Identifier || m_scanner->currentLiteral() != "from")
+			fatalParserError("Expected \"from\".");
+		m_scanner->next();
+		if (m_scanner->currentToken() != Token::StringLiteral)
+			fatalParserError("Expected import path.");
+		path = getLiteralAndAdvance();
+	}
 	nodeFactory.markEndPosition();
 	expectToken(Token::Semicolon);
-	return nodeFactory.createNode<ImportDirective>(url);
+	return nodeFactory.createNode<ImportDirective>(path, unitAlias, move(symbolAliases));
 }
 
 ASTPointer<ContractDefinition> Parser::parseContractDefinition(bool _isLibrary)
@@ -171,7 +222,7 @@ ASTPointer<ContractDefinition> Parser::parseContractDefinition(bool _isLibrary)
 		else if (currentTokenValue == Token::Using)
 			subNodes.push_back(parseUsingDirective());
 		else
-			fatalParserError(std::string("Function, variable, struct or modifier declaration expected."));
+			fatalParserError(string("Function, variable, struct or modifier declaration expected."));
 	}
 	nodeFactory.markEndPosition();
 	expectToken(Token::RBrace);
@@ -250,7 +301,7 @@ ASTPointer<FunctionDefinition> Parser::parseFunctionDefinition(ASTString const*
 		else if (Token::isVisibilitySpecifier(token))
 		{
 			if (visibility != Declaration::Visibility::Default)
-				fatalParserError(std::string("Multiple visibility specifiers."));
+				fatalParserError(string("Multiple visibility specifiers."));
 			visibility = parseVisibilitySpecifier(token);
 		}
 		else
@@ -327,7 +378,7 @@ ASTPointer<EnumDefinition> Parser::parseEnumDefinition()
 			break;
 		expectToken(Token::Comma);
 		if (m_scanner->currentToken() != Token::Identifier)
-			fatalParserError(std::string("Expected Identifier after ','"));
+			fatalParserError(string("Expected Identifier after ','"));
 	}
 
 	nodeFactory.markEndPosition();
@@ -363,7 +414,7 @@ ASTPointer<VariableDeclaration> Parser::parseVariableDeclaration(
 		if (_options.isStateVariable && Token::isVariableVisibilitySpecifier(token))
 		{
 			if (visibility != Declaration::Visibility::Default)
-				fatalParserError(std::string("Visibility already specified."));
+				fatalParserError(string("Visibility already specified."));
 			visibility = parseVisibilitySpecifier(token);
 		}
 		else
@@ -375,9 +426,9 @@ ASTPointer<VariableDeclaration> Parser::parseVariableDeclaration(
 			else if (_options.allowLocationSpecifier && Token::isLocationSpecifier(token))
 			{
 				if (location != VariableDeclaration::Location::Default)
-					fatalParserError(std::string("Location already specified."));
+					fatalParserError(string("Location already specified."));
 				if (!type)
-					fatalParserError(std::string("Location specifier needs explicit type name."));
+					fatalParserError(string("Location specifier needs explicit type name."));
 				location = (
 					token == Token::Memory ?
 					VariableDeclaration::Location::Memory :
@@ -532,7 +583,7 @@ ASTPointer<TypeName> Parser::parseTypeName(bool _allowVar)
 	else if (token == Token::Var)
 	{
 		if (!_allowVar)
-			fatalParserError(std::string("Expected explicit type name."));
+			fatalParserError(string("Expected explicit type name."));
 		m_scanner->next();
 	}
 	else if (token == Token::Mapping)
@@ -551,7 +602,7 @@ ASTPointer<TypeName> Parser::parseTypeName(bool _allowVar)
 		type = nodeFactory.createNode<UserDefinedTypeName>(identifierPath);
 	}
 	else
-		fatalParserError(std::string("Expected type name"));
+		fatalParserError(string("Expected type name"));
 
 	if (type)
 		// Parse "[...]" postfixes for arrays.
@@ -574,7 +625,7 @@ ASTPointer<Mapping> Parser::parseMapping()
 	expectToken(Token::Mapping);
 	expectToken(Token::LParen);
 	if (!Token::isElementaryTypeName(m_scanner->currentToken()))
-		fatalParserError(std::string("Expected elementary type name for mapping key type"));
+		fatalParserError(string("Expected elementary type name for mapping key type"));
 	ASTPointer<ElementaryTypeName> keyType;
 	keyType = ASTNodeFactory(*this).createNode<ElementaryTypeName>(m_scanner->currentToken());
 	m_scanner->next();
@@ -1072,7 +1123,7 @@ ASTPointer<Expression> Parser::parsePrimaryExpression()
 			m_scanner->next();
 		}
 		else
-			fatalParserError(std::string("Expected primary expression."));
+			fatalParserError(string("Expected primary expression."));
 		break;
 	}
 	return expression;
@@ -1221,8 +1272,7 @@ Token::Value Parser::expectAssignmentOperator()
 	Token::Value op = m_scanner->currentToken();
 	if (!Token::isAssignmentOp(op))
 		fatalParserError(
-			std::string("Expected assignment operator ") +
-			string(" got '") +
+			string("Expected assignment operator,  got '") +
 			string(Token::name(m_scanner->currentToken())) +
 			string("'")
 		);
@@ -1234,8 +1284,7 @@ ASTPointer<ASTString> Parser::expectIdentifierToken()
 {
 	if (m_scanner->currentToken() != Token::Identifier)
 		fatalParserError(
-			std::string("Expected identifier ") +
-			string(" got '") +
+			string("Expected identifier, got '") +
 			string(Token::name(m_scanner->currentToken())) +
 			string("'")
 		);
diff --git a/test/libsolidity/Imports.cpp b/test/libsolidity/Imports.cpp
index ab8e2257..57239cb9 100644
--- a/test/libsolidity/Imports.cpp
+++ b/test/libsolidity/Imports.cpp
@@ -93,6 +93,14 @@ BOOST_AUTO_TEST_CASE(relative_import_multiplex)
 	BOOST_CHECK(c.compile());
 }
 
+BOOST_AUTO_TEST_CASE(simple_alias)
+{
+	CompilerStack c;
+	c.addSource("a", "contract A {}");
+	c.addSource("dir/a/b/c", "import \"../../.././a\" as x; contract B { function() { x.A r = x.A(20); } }");
+	BOOST_CHECK(c.compile());
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }
diff --git a/test/libsolidity/SolidityParser.cpp b/test/libsolidity/SolidityParser.cpp
index e6c8a8d8..5c5a9f68 100644
--- a/test/libsolidity/SolidityParser.cpp
+++ b/test/libsolidity/SolidityParser.cpp
@@ -1047,6 +1047,27 @@ BOOST_AUTO_TEST_CASE(using_for)
 	BOOST_CHECK(successParse(text));
 }
 
+BOOST_AUTO_TEST_CASE(complex_import)
+{
+	char const* text = R"(
+		import "abc" as x;
+		import * as x from "abc";
+		import {a as b, c as d, f} from "def";
+		contract x {}
+	)";
+	BOOST_CHECK(successParse(text));
+}
+
+BOOST_AUTO_TEST_CASE(from_is_not_keyword)
+{
+	// "from" is not a keyword although it is used as a keyword in import directives.
+	char const* text = R"(
+		contract from {
+		}
+	)";
+	BOOST_CHECK(successParse(text));
+}
+
 BOOST_AUTO_TEST_CASE(inline_array_declaration)
 {
 	char const* text = R"(