Merge pull request #3535 from ethereum/fixShadowing

Fix shadowing detection for aliases

3 files changed, 26 insertions, 3 deletions

diff --git a/Changelog.md b/Changelog.md
index d6b83d6e..4e6e1b92 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -7,6 +7,7 @@ Features:
 
 Bugfixes:
  * JSON-AST: Add "documentation" property to function, event and modifier definition.
+ * Resolver: Properly determine shadowing for imports with aliases.
  * Standard JSON: catch errors properly when invalid "sources" are passed
  * Type Checker: Properly warn when using ``_offset`` and ``_slot`` for constants in inline assembly.
 
diff --git a/libsolidity/analysis/NameAndTypeResolver.cpp b/libsolidity/analysis/NameAndTypeResolver.cpp
index 5e4d414b..662792a3 100644
--- a/libsolidity/analysis/NameAndTypeResolver.cpp
+++ b/libsolidity/analysis/NameAndTypeResolver.cpp
@@ -457,9 +457,10 @@ bool DeclarationRegistrationHelper::registerDeclaration(
 	if (!_errorLocation)
 		_errorLocation = &_declaration.location();
 
+	string name = _name ? *_name : _declaration.name();
 	Declaration const* shadowedDeclaration = nullptr;
-	if (_warnOnShadow && !_declaration.name().empty() && _container.enclosingContainer())
-		for (auto const* decl: _container.enclosingContainer()->resolveName(_declaration.name(), true))
+	if (_warnOnShadow && !name.empty() && _container.enclosingContainer())
+		for (auto const* decl: _container.enclosingContainer()->resolveName(name, true))
 			shadowedDeclaration = decl;
 
 	if (!_container.registerDeclaration(_declaration, _name, !_declaration.isVisibleInContract()))
diff --git a/test/libsolidity/Imports.cpp b/test/libsolidity/Imports.cpp
index 03287b28..dc1174f4 100644
--- a/test/libsolidity/Imports.cpp
+++ b/test/libsolidity/Imports.cpp
@@ -266,7 +266,28 @@ BOOST_AUTO_TEST_CASE(shadowing_builtins_with_multiple_imports)
 	}
 }
 
-
+BOOST_AUTO_TEST_CASE(shadowing_builtins_with_alias)
+{
+	CompilerStack c;
+	c.addSource("B.sol", "contract C {} pragma solidity >=0.0;");
+	c.addSource("b", R"(
+		pragma solidity >=0.0;
+		import {C as msg} from "B.sol";
+	)");
+	BOOST_CHECK(c.compile());
+	auto numErrors = c.errors().size();
+	// Sometimes we get the prerelease warning, sometimes not.
+	BOOST_CHECK(1 <= numErrors && numErrors <= 2);
+	for (auto const& e: c.errors())
+	{
+		string const* msg = e->comment();
+		BOOST_REQUIRE(msg);
+		BOOST_CHECK(
+			msg->find("pre-release") != string::npos ||
+			msg->find("shadows a builtin symbol") != string::npos
+		);
+	}
+}
 
 BOOST_AUTO_TEST_SUITE_END()