From 2d0daae7968f5237231e50173a391652eca75674 Mon Sep 17 00:00:00 2001
From: Erik Kundt <erik@ethereum.org>
Date: Thu, 21 Feb 2019 16:38:02 +0100
Subject: [PATCH] Disallows index access on contracts and libraries.

---
 Changelog.md                                               | 1 +
 libsolidity/analysis/TypeChecker.cpp                       | 2 ++
 .../syntaxTests/array/invalid/contract_index_access.sol    | 7 +++++++
 .../syntaxTests/array/invalid/library_index_access.sol     | 7 +++++++
 4 files changed, 17 insertions(+)
 create mode 100644 test/libsolidity/syntaxTests/array/invalid/contract_index_access.sol
 create mode 100644 test/libsolidity/syntaxTests/array/invalid/library_index_access.sol

diff --git a/Changelog.md b/Changelog.md
index fed2c953f..752808afc 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -19,6 +19,7 @@ Bugfixes:
  * Inline Assembly: Proper error message for missing variables.
  * Optimizer: Fix internal error related to unused tag removal across assemblies. This never generated any invalid code.
  * SMTChecker: Fixed crash when used with fixed-sized arrays.
+ * TypeChecker: Fix internal error and disallow index access on contracts and libraries.
  * Yul: Properly detect name clashes with functions before their declaration.
  * Yul: Take builtin functions into account in the compilability checker.
 
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 0208fc7ac..a431930f6 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -2208,6 +2208,8 @@ bool TypeChecker::visit(IndexAccess const& _access)
 	case Type::Category::TypeType:
 	{
 		TypeType const& typeType = dynamic_cast<TypeType const&>(*baseType);
+		if (dynamic_cast<ContractType const*>(typeType.actualType().get()))
+			m_errorReporter.typeError(_access.location(), "Index access for contracts or libraries is not possible.");
 		if (!index)
 			resultType = make_shared<TypeType>(make_shared<ArrayType>(DataLocation::Memory, typeType.actualType()));
 		else
diff --git a/test/libsolidity/syntaxTests/array/invalid/contract_index_access.sol b/test/libsolidity/syntaxTests/array/invalid/contract_index_access.sol
new file mode 100644
index 000000000..9f79f3018
--- /dev/null
+++ b/test/libsolidity/syntaxTests/array/invalid/contract_index_access.sol
@@ -0,0 +1,7 @@
+contract C {
+    function f() view public {
+        C[0];
+    }
+}
+// ----
+// TypeError: (52-56): Index access for contracts or libraries is not possible.
diff --git a/test/libsolidity/syntaxTests/array/invalid/library_index_access.sol b/test/libsolidity/syntaxTests/array/invalid/library_index_access.sol
new file mode 100644
index 000000000..442150c97
--- /dev/null
+++ b/test/libsolidity/syntaxTests/array/invalid/library_index_access.sol
@@ -0,0 +1,7 @@
+library C {
+    function f() view public {
+        C[0];
+    }
+}
+// ----
+// TypeError: (51-55): Index access for contracts or libraries is not possible.