Merge pull request #4796 from ethereum/structs-in-interfaces

[BREAKING] Adds support for structs in interfaces.

Changelog.md

@@ -75,6 +75,7 @@ Language Features:
  * General: Scoping rules now follow the C99-style.
  * General: Allow ``enum``s in interfaces.
  * General: Allow ``mapping`` storage pointers as arguments and return values in all internal functions.
+ * General: Allow ``struct``s in interfaces.
 
 Compiler Features:
  * C API (``libsolc``): Export the ``solidity_license``, ``solidity_version`` and ``solidity_compile`` methods.

libsolidity/analysis/TypeChecker.cpp

@@ -580,9 +580,6 @@ void TypeChecker::endVisit(UsingForDirective const& _usingFor)
 
 bool TypeChecker::visit(StructDefinition const& _struct)
 {
-	if (m_scope->contractKind() == ContractDefinition::ContractKind::Interface)
-		m_errorReporter.typeError(_struct.location(), "Structs cannot be defined in interfaces.");
-
 	for (ASTPointer<VariableDeclaration> const& member: _struct.members())
 		if (!type(*member)->canBeStored())
 			m_errorReporter.typeError(member->location(), "Type cannot be used in struct.");
@@ -610,7 +607,10 @@ bool TypeChecker::visit(StructDefinition const& _struct)
 	if (CycleDetector<StructDefinition>(visitor).run(_struct) != nullptr)
 		m_errorReporter.fatalTypeError(_struct.location(), "Recursive struct definition.");
 
+	bool insideStruct = true;
+	swap(insideStruct, m_insideStruct);
 	ASTNode::listAccept(_struct.members(), *this);
+	m_insideStruct = insideStruct;
 
 	return false;
 }
@@ -693,10 +693,12 @@ bool TypeChecker::visit(FunctionDefinition const& _function)
 bool TypeChecker::visit(VariableDeclaration const& _variable)
 {
 	// Forbid any variable declarations inside interfaces unless they are part of
-	// a function's input/output parameters.
+	// * a function's input/output parameters,
+	// * or inside of a struct definition.
 	if (
 		m_scope->contractKind() == ContractDefinition::ContractKind::Interface
 		&& !_variable.isCallableParameter()
+		&& !m_insideStruct
 	)
 		m_errorReporter.typeError(_variable.location(), "Variables cannot be declared in interfaces.");
 

libsolidity/analysis/TypeChecker.h

@@ -149,6 +149,9 @@ private:
 	/// Flag indicating whether we are currently inside an EmitStatement.
 	bool m_insideEmitStatement = false;
 
+	/// Flag indicating whether we are currently inside a StructDefinition.
+	bool m_insideStruct = false;
+
 	ErrorReporter& m_errorReporter;
 };
 

test/libsolidity/SolidityEndToEndTest.cpp

@@ -4755,6 +4755,68 @@ BOOST_AUTO_TEST_CASE(constructing_enums_from_ints)
 	ABI_CHECK(callContractFunction("test()"), encodeArgs(1));
 }
 
+BOOST_AUTO_TEST_CASE(struct_referencing)
+{
+	static char const* sourceCode = R"(
+		pragma experimental ABIEncoderV2;
+		interface I {
+			struct S { uint a; }
+		}
+		library L {
+			struct S { uint b; uint a; }
+			function f() public pure returns (S) {
+				S memory s;
+				s.a = 3;
+				return s;
+			}
+			function g() public pure returns (I.S) {
+				I.S memory s;
+				s.a = 4;
+				return s;
+			}
+			// argument-dependant lookup tests
+			function a(I.S memory) public pure returns (uint) { return 1; }
+			function a(S memory) public pure returns (uint) { return 2; }
+		}
+		contract C is I {
+			function f() public pure returns (S) {
+				S memory s;
+				s.a = 1;
+				return s;
+			}
+			function g() public pure returns (I.S) {
+				I.S memory s;
+				s.a = 2;
+				return s;
+			}
+			function h() public pure returns (L.S) {
+				L.S memory s;
+				s.a = 5;
+				return s;
+			}
+			function x() public pure returns (L.S) {
+				return L.f();
+			}
+			function y() public pure returns (I.S) {
+				return L.g();
+			}
+			function a1() public pure returns (uint) { S memory s; return L.a(s); }
+			function a2() public pure returns (uint) { L.S memory s; return L.a(s); }
+		}
+	)";
+	compileAndRun(sourceCode, 0, "L");
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(0, 3));
+	ABI_CHECK(callContractFunction("g()"), encodeArgs(4));
+	compileAndRun(sourceCode, 0, "C", bytes(), map<string, Address>{ {"L", m_contractAddress}});
+	ABI_CHECK(callContractFunction("f()"), encodeArgs(1));
+	ABI_CHECK(callContractFunction("g()"), encodeArgs(2));
+	ABI_CHECK(callContractFunction("h()"), encodeArgs(0, 5));
+	ABI_CHECK(callContractFunction("x()"), encodeArgs(0, 3));
+	ABI_CHECK(callContractFunction("y()"), encodeArgs(4));
+	ABI_CHECK(callContractFunction("a1()"), encodeArgs(1));
+	ABI_CHECK(callContractFunction("a2()"), encodeArgs(2));
+}
+
 BOOST_AUTO_TEST_CASE(enum_referencing)
 {
 	char const* sourceCode = R"(

test/libsolidity/syntaxTests/nameAndTypeResolution/419_interface_structs.sol

@@ -1,9 +1,6 @@
 interface I {
     struct A {
-        // This is currently expected to break, but it *may* change in the future.
         int dummy;
     }
 }
 // ----
-// TypeError: (18-136): Structs cannot be defined in interfaces.
-// TypeError: (120-129): Variables cannot be declared in interfaces.