4 files changed, 81 insertions, 16 deletions

diff --git a/libsolidity/analysis/DeclarationContainer.cpp b/libsolidity/analysis/DeclarationContainer.cpp
index ac56562e..042b7a6a 100644
--- a/libsolidity/analysis/DeclarationContainer.cpp
+++ b/libsolidity/analysis/DeclarationContainer.cpp
@@ -49,6 +49,8 @@ Declaration const* DeclarationContainer::conflictingDeclaration(
 			if (!dynamic_cast<FunctionDefinition const*>(declaration))
 				return declaration;
 	}
+	else if (declarations.size() == 1 && declarations.front() == &_declaration)
+		return nullptr;
 	else if (!declarations.empty())
 		return declarations.front();
 
@@ -73,13 +75,12 @@ bool DeclarationContainer::registerDeclaration(
 		m_declarations.erase(*_name);
 		m_invisibleDeclarations.erase(*_name);
 	}
-	else if (conflictingDeclaration(_declaration))
+	else if (conflictingDeclaration(_declaration, _name))
 		return false;
 
-	if (_invisible)
-		m_invisibleDeclarations[*_name].push_back(&_declaration);
-	else
-		m_declarations[*_name].push_back(&_declaration);
+	vector<Declaration const*>& decls = _invisible ? m_invisibleDeclarations[*_name] : m_declarations[*_name];
+	if (!contains(decls, &_declaration))
+		decls.push_back(&_declaration);
 	return true;
 }
 
diff --git a/libsolidity/analysis/NameAndTypeResolver.cpp b/libsolidity/analysis/NameAndTypeResolver.cpp
index 96ffdd6e..5e407383 100644
--- a/libsolidity/analysis/NameAndTypeResolver.cpp
+++ b/libsolidity/analysis/NameAndTypeResolver.cpp
@@ -76,23 +76,58 @@ bool NameAndTypeResolver::performImports(SourceUnit& _sourceUnit, map<string, So
 			string const& path = imp->annotation().absolutePath;
 			if (!_sourceUnits.count(path))
 			{
-				reportDeclarationError( node->location(),
-					"Import \"" +
-					path +
-					"\" (referenced as \"" +
-					imp->path() +
-					"\") not found."
+				reportDeclarationError(
+					imp->location(),
+					"Import \"" + path + "\" (referenced as \"" + imp->path() + "\") not found."
 				);
 				error = true;
+				continue;
 			}
+			auto scope = m_scopes.find(_sourceUnits.at(path));
+			solAssert(scope != end(m_scopes), "");
+			if (!imp->symbolAliases().empty())
+				for (auto const& alias: imp->symbolAliases())
+				{
+					auto declarations = scope->second->resolveName(alias.first->name(), false);
+					if (declarations.empty())
+					{
+						reportDeclarationError(
+							imp->location(),
+							"Declaration \"" +
+							alias.first->name() +
+							"\" not found in \"" +
+							path +
+							"\" (referenced as \"" +
+							imp->path() +
+							"\")."
+						);
+						error = true;
+					}
+					else
+						for (Declaration const* declaration: declarations)
+						{
+							ASTString const* name = alias.second ? alias.second.get() : &declaration->name();
+							if (!target.registerDeclaration(*declaration, name))
+							{
+								reportDeclarationError(
+									imp->location(),
+									"Identifier \"" + *name + "\" already declared."
+								);
+								error = true;
+							}
+						}
+				}
 			else if (imp->name().empty())
-			{
-				auto scope = m_scopes.find(_sourceUnits.at(path));
-				solAssert(scope != end(m_scopes), "");
 				for (auto const& nameAndDeclaration: scope->second->declarations())
 					for (auto const& declaration: nameAndDeclaration.second)
-						target.registerDeclaration(*declaration, &nameAndDeclaration.first);
-			}
+						if (!target.registerDeclaration(*declaration, &nameAndDeclaration.first))
+						{
+							reportDeclarationError(
+								imp->location(),
+								"Identifier \"" + nameAndDeclaration.first + "\" already declared."
+							);
+							error = true;
+						}
 		}
 	return !error;
 }
diff --git a/libsolidity/ast/AST.h b/libsolidity/ast/AST.h
index 604a12a0..4baf95d3 100644
--- a/libsolidity/ast/AST.h
+++ b/libsolidity/ast/AST.h
@@ -201,6 +201,10 @@ public:
 	virtual void accept(ASTConstVisitor& _visitor) const override;
 
 	ASTString const& path() const { return *m_path; }
+	std::vector<std::pair<ASTPointer<Identifier>, ASTPointer<ASTString>>> const& symbolAliases() const
+	{
+		return m_symbolAliases;
+	}
 	virtual ImportAnnotation& annotation() const override;
 
 	virtual TypePointer type() const override;
diff --git a/test/libsolidity/Imports.cpp b/test/libsolidity/Imports.cpp
index f0f67785..c074b332 100644
--- a/test/libsolidity/Imports.cpp
+++ b/test/libsolidity/Imports.cpp
@@ -101,6 +101,31 @@ BOOST_AUTO_TEST_CASE(simple_alias)
 	BOOST_CHECK(c.compile());
 }
 
+BOOST_AUTO_TEST_CASE(complex_import)
+{
+	CompilerStack c;
+	c.addSource("a", "contract A {} contract B {} contract C { struct S { uint a; } }");
+	c.addSource("b", "import \"a\" as x; import {B as b, C as c, C} from \"a\"; "
+				"contract D is b { function f(c.S var1, x.C.S var2, C.S var3) internal {} }");
+	BOOST_CHECK(c.compile());
+}
+
+BOOST_AUTO_TEST_CASE(name_clash_in_import)
+{
+	CompilerStack c;
+	c.addSource("a", "contract A {}");
+	c.addSource("b", "import \"a\"; contract A {} ");
+	BOOST_CHECK(!c.compile());
+	c.addSource("b", "import \"a\" as A; contract A {} ");
+	BOOST_CHECK(!c.compile());
+	c.addSource("b", "import {A as b} from \"a\"; contract b {} ");
+	BOOST_CHECK(!c.compile());
+	c.addSource("b", "import {A} from \"a\"; contract A {} ");
+	BOOST_CHECK(!c.compile());
+	c.addSource("b", "import {A} from \"a\"; contract B {} ");
+	BOOST_CHECK(c.compile());
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }