Merge pull request #10051 from ethereum/contractArrayTypeStatement

Allow arrays of contract types as type expressions e.g. for abi.decode.

Changelog.md

@@ -22,6 +22,7 @@ Bugfixes:
  * Code generator: Fix internal compiler error when referencing members via module name but not using the reference.
  * Code generator: Fix ``ABIEncoderV2`` pragma from the current module affecting inherited functions and applied modifiers.
  * Code generator: Use revert instead of invalid opcode for out-of-bounds array index access in getter.
+ * Type Checker: Allow arrays of contract types as type expressions and as arguments for ``abi.decode``.
  * Type Checker: Disallow invalid use of library names as type name.
  * Type Checker: Fix internal compiler error caused by storage parameters with nested mappings in libraries.
  * Name Resolver: Fix shadowing/same-name warnings for later declarations.

libsolidity/analysis/TypeChecker.cpp

@@ -2915,8 +2915,9 @@ 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()))
+		if (auto const* contractType = dynamic_cast<ContractType const*>(typeType.actualType()))
-			m_errorReporter.typeError(2876_error, _access.location(), "Index access for contracts or libraries is not possible.");
+			if (contractType->contractDefinition().isLibrary())
+				m_errorReporter.typeError(2876_error, _access.location(), "Index access for library types and arrays of libraries are not possible.");
 		if (!index)
 			resultType = TypeProvider::typeType(TypeProvider::array(DataLocation::Memory, typeType.actualType()));
 		else

test/libsolidity/semanticTests/abiencodedecode/contract_array.sol

@@ -0,0 +1,17 @@
+contract C {
+  function f(bytes calldata x) public returns (C[] memory) {
+    return abi.decode(x, (C[]));
+  }
+  function g() public returns (bytes memory) {
+    C[] memory c = new C[](3);
+    c[0] = C(address(0x42));
+    c[1] = C(address(0x21));
+    c[2] = C(address(0x23));
+    return abi.encode(c);
+  }
+}
+// ====
+// compileViaYul: also
+// ----
+// f(bytes): 0x20, 0xA0, 0x20, 3, 0x01, 0x02, 0x03 -> 0x20, 3, 0x01, 0x02, 0x03
+// g() -> 0x20, 0xa0, 0x20, 3, 0x42, 0x21, 0x23

test/libsolidity/semanticTests/abiencodedecode/contract_array_v2.sol

@@ -0,0 +1,20 @@
+pragma experimental ABIEncoderV2;
+contract C {
+  function f(bytes calldata x) public returns (C[] memory) {
+    return abi.decode(x, (C[]));
+  }
+  function g() public returns (bytes memory) {
+    C[] memory c = new C[](3);
+    c[0] = C(address(0x42));
+    c[1] = C(address(0x21));
+    c[2] = C(address(0x23));
+    return abi.encode(c);
+  }
+}
+// ====
+// compileViaYul: also
+// ----
+// f(bytes): 0x20, 0xA0, 0x20, 3, 0x01, 0x02, 0x03 -> 0x20, 3, 0x01, 0x02, 0x03
+// f(bytes): 0x20, 0x60, 0x20, 1, 0x0102030405060708090a0b0c0d0e0f1011121314 -> 0x20, 1, 0x0102030405060708090a0b0c0d0e0f1011121314
+// f(bytes): 0x20, 0x60, 0x20, 1, 0x0102030405060708090a0b0c0d0e0f101112131415 -> FAILURE
+// g() -> 0x20, 0xa0, 0x20, 3, 0x42, 0x21, 0x23

test/libsolidity/syntaxTests/array/contract_index_access.sol

@@ -0,0 +1,8 @@
+contract C {
+    function f() view public {
+        C[0];
+    }
+}
+// ----
+// Warning 6133: (52-56): Statement has no effect.
+// Warning 2018: (17-63): Function state mutability can be restricted to pure

test/libsolidity/syntaxTests/array/invalid/contract_index_access.sol

@@ -1,7 +0,0 @@
-contract C {
-    function f() view public {
-        C[0];
-    }
-}
-// ----
-// TypeError 2876: (52-56): Index access for contracts or libraries is not possible.

test/libsolidity/syntaxTests/array/invalid/library_index_access.sol

@@ -4,4 +4,4 @@ library C {
     }
 }
 // ----
-// TypeError 2876: (51-55): Index access for contracts or libraries is not possible.
+// TypeError 2876: (51-55): Index access for library types and arrays of libraries are not possible.

test/libsolidity/syntaxTests/indexing/index_range_access_assert.sol

@@ -3,4 +3,3 @@ contract s{}
 function f() {s[:][];}
 // ----
 // TypeError 1760: (53-57): Types cannot be sliced.
-// TypeError 2876: (53-59): Index access for contracts or libraries is not possible.

test/libsolidity/syntaxTests/specialFunctions/abidecode/contract_array.sol

@@ -0,0 +1,5 @@
+contract C {
+	function f(bytes calldata x) public pure returns (C[] memory c) {
+		c = abi.decode(x, (C[]));
+	}
+}