Merge pull request #12921 from ethereum/add_event_and_error_selector_fields_on_the_line_of_function_selector_field

Adding event and error selector fields

Changelog.md

@@ -1,6 +1,8 @@
 ### 0.8.15 (unreleased)
 
 Language Features:
+* General: Add `E.selector` for a non-anonymous event `E` to access the 32-byte selector topic.
+* General: Errors and Events allow qualified access from other contracts.
 
 
 Compiler Features:

docs/contracts/events.rst

@@ -73,6 +73,16 @@ four indexed arguments rather than three.
     In particular, it is possible to "fake" the signature of another event
     using an anonymous event.
 
+Members of Events
+=================
+
+- ``event.selector``: For non-anonymous events, this is a ``bytes32`` value
+  containing the ``keccak256`` hash of the event signature, as used in the default topic.
+
+
+Example
+=======
+
 .. code-block:: solidity
 
     // SPDX-License-Identifier: GPL-3.0

libsolidity/ast/AST.h

@@ -1216,7 +1216,7 @@ public:
 	FunctionTypePointer functionType(bool /*_internal*/) const override;
 
 	bool isVisibleInDerivedContracts() const override { return true; }
-	bool isVisibleViaContractTypeAccess() const override { return false; /* TODO */ }
+	bool isVisibleViaContractTypeAccess() const override { return true; }
 
 	EventDefinitionAnnotation& annotation() const override;
 

libsolidity/ast/Types.cpp

@@ -3335,6 +3335,12 @@ MemberList::MemberMap FunctionType::nativeMembers(ASTNode const* _scope) const
 	}
 	case Kind::Error:
 		return {{"selector", TypeProvider::fixedBytes(4)}};
+	case Kind::Event:
+	{
+		if (!(dynamic_cast<EventDefinition const&>(declaration()).isAnonymous()))
+			return {{"selector", TypeProvider::fixedBytes(32)}};
+		return MemberList::MemberMap();
+	}
 	default:
 		return MemberList::MemberMap();
 	}

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1602,9 +1602,14 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 	{
 		if (functionType->hasDeclaration())
 		{
-			m_context << functionType->externalIdentifier();
-			/// need to store it as bytes4
-			utils().leftShiftNumberOnStack(224);
+			if (functionType->kind() == FunctionType::Kind::Event)
+				m_context << u256(h256::Arith(util::keccak256(functionType->externalSignature())));
+			else
+			{
+				m_context << functionType->externalIdentifier();
+				/// need to store it as bytes4
+				utils().leftShiftNumberOnStack(224);
+			}
 			return false;
 		}
 		else if (auto const* expr = dynamic_cast<MemberAccess const*>(&_memberAccess.expression()))
@@ -1775,9 +1780,13 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 		if (member == "selector")
 		{
 			auto const& functionType = dynamic_cast<FunctionType const&>(*_memberAccess.expression().annotation().type);
+			// all events should have already been caught by this stage
+			solAssert(!(functionType.kind() == FunctionType::Kind::Event));
+
 			if (functionType.kind() == FunctionType::Kind::External)
 				CompilerUtils(m_context).popStackSlots(functionType.sizeOnStack() - 2);
 			m_context << Instruction::SWAP1 << Instruction::POP;
+
 			/// need to store it as bytes4
 			utils().leftShiftNumberOnStack(224);
 		}

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -1785,7 +1785,20 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 					functionType.declaration().isPartOfExternalInterface(),
 					""
 				);
-				define(IRVariable{_memberAccess}) << formatNumber(functionType.externalIdentifier() << 224) << "\n";
+				define(IRVariable{_memberAccess}) << formatNumber(
+					util::selectorFromSignature(functionType.externalSignature())
+				) << "\n";
+			}
+			else if (functionType.kind() == FunctionType::Kind::Event)
+			{
+				solAssert(functionType.hasDeclaration());
+				solAssert(functionType.kind() == FunctionType::Kind::Event);
+				solAssert(
+					!(dynamic_cast<EventDefinition const&>(functionType.declaration()).isAnonymous())
+				);
+				define(IRVariable{_memberAccess}) << formatNumber(
+					u256(h256::Arith(util::keccak256(functionType.externalSignature())))
+				) << "\n";
 			}
 			else
 				solAssert(false, "Invalid use of .selector: " + functionType.toString(false));

test/libsolidity/semanticTests/error/error_selector.sol

@@ -0,0 +1,48 @@
+library L {
+    error E();
+}
+library S {
+    error E(uint);
+}
+library T {
+    error E();
+}
+
+error E();
+
+interface I {
+    error E();
+    function f() external pure;
+}
+
+contract D {
+    error F();
+}
+
+contract C is D {
+    function test1() public pure returns (bytes4, bytes4, bytes4, bytes4) {
+        assert(L.E.selector == T.E.selector);
+        assert(L.E.selector != S.E.selector);
+        assert(E.selector == L.E.selector);
+        assert(I.E.selector == L.E.selector);
+        return (L.E.selector, S.E.selector, E.selector, I.E.selector);
+    }
+
+    bytes4 s1 = L.E.selector;
+    bytes4 s2 = S.E.selector;
+    bytes4 s3 = T.E.selector;
+    bytes4 s4 = I.E.selector;
+    function test2() external returns (bytes4, bytes4, bytes4, bytes4) {
+        return (s1, s2, s3, s4);
+    }
+
+    function test3() external returns (bytes4) {
+        return (F.selector);
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// test1() -> 0x92bbf6e800000000000000000000000000000000000000000000000000000000, 0x2ff06700000000000000000000000000000000000000000000000000000000, 0x92bbf6e800000000000000000000000000000000000000000000000000000000, 0x92bbf6e800000000000000000000000000000000000000000000000000000000
+// test2() -> 0x92bbf6e800000000000000000000000000000000000000000000000000000000, 0x2ff06700000000000000000000000000000000000000000000000000000000, 0x92bbf6e800000000000000000000000000000000000000000000000000000000, 0x92bbf6e800000000000000000000000000000000000000000000000000000000
+// test3() -> 0x28811f5900000000000000000000000000000000000000000000000000000000

test/libsolidity/semanticTests/events/event_selector.sol

@@ -0,0 +1,47 @@
+library L {
+    event E();
+}
+library S {
+    event E(uint);
+}
+library T {
+    event E();
+}
+interface I {
+    event E();
+}
+
+contract D {
+    event F();
+}
+
+contract C is D {
+    function test1() external pure returns (bytes32, bytes32, bytes32) {
+        assert(L.E.selector == T.E.selector);
+        assert(I.E.selector == L.E.selector);
+
+        assert(L.E.selector != S.E.selector);
+        assert(T.E.selector != S.E.selector);
+        assert(I.E.selector != S.E.selector);
+
+        return (L.E.selector, S.E.selector, I.E.selector);
+    }
+
+    bytes32 s1 = L.E.selector;
+    bytes32 s2 = S.E.selector;
+    bytes32 s3 = T.E.selector;
+    bytes32 s4 = I.E.selector;
+    function test2() external returns (bytes32, bytes32, bytes32, bytes32) {
+        return (s1, s2, s3, s4);
+    }
+
+    function test3() external returns (bytes32) {
+        return (F.selector);
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// test1() -> 0x92bbf6e823a631f3c8e09b1c8df90f378fb56f7fbc9701827e1ff8aad7f6a028, 0x2ff0672f372fbe844b353429d4510ea5e43683af134c54f75f789ff57bc0c0, 0x92bbf6e823a631f3c8e09b1c8df90f378fb56f7fbc9701827e1ff8aad7f6a028
+// test2() -> 0x92bbf6e823a631f3c8e09b1c8df90f378fb56f7fbc9701827e1ff8aad7f6a028, 0x2ff0672f372fbe844b353429d4510ea5e43683af134c54f75f789ff57bc0c0, 0x92bbf6e823a631f3c8e09b1c8df90f378fb56f7fbc9701827e1ff8aad7f6a028, 0x92bbf6e823a631f3c8e09b1c8df90f378fb56f7fbc9701827e1ff8aad7f6a028
+// test3() -> 0x28811f5935c16a099486acb976b3a6b4942950a1425a74e9eb3e9b7f7135e12a

test/libsolidity/semanticTests/events/simple.sol

@@ -0,0 +1,17 @@
+contract C {
+    event E();
+}
+
+contract Test {
+    event E(uint256, uint256);
+    function f() public {
+        emit C.E();
+        emit E(1,2);
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// f() ->
+// ~ emit E()
+// ~ emit E(uint256,uint256): 0x01, 0x02

test/libsolidity/syntaxTests/errors/error_selector_syntax.sol

@@ -0,0 +1,48 @@
+library L {
+    error E();
+}
+library S {
+    error E(uint);
+}
+library T {
+    error E();
+}
+
+error E();
+
+interface I {
+    error E();
+    function f() external pure;
+}
+
+contract D {
+    error F();
+}
+
+contract C is D {
+    function test1() public pure returns (bytes4, bytes4, bytes4, bytes4) {
+        assert(L.E.selector == T.E.selector);
+        assert(L.E.selector != S.E.selector);
+        assert(E.selector == L.E.selector);
+        assert(I.E.selector == L.E.selector);
+        return (L.E.selector, S.E.selector, E.selector, I.E.selector);
+    }
+
+    bytes4 s1 = L.E.selector;
+    bytes4 s2 = S.E.selector;
+    bytes4 s3 = T.E.selector;
+    bytes4 s4 = I.E.selector;
+
+    function test2() view external returns (bytes4, bytes4, bytes4, bytes4) {
+        return (s1, s2, s3, s4);
+    }
+
+    function test3() pure external returns (bytes4) {
+        return (F.selector);
+    }
+}
+// ----
+// Warning 2519: (16-26): This declaration shadows an existing declaration.
+// Warning 2519: (45-59): This declaration shadows an existing declaration.
+// Warning 2519: (78-88): This declaration shadows an existing declaration.
+// Warning 2519: (122-132): This declaration shadows an existing declaration.

test/libsolidity/syntaxTests/events/event_selector_library_called_inside_function.sol

@@ -0,0 +1,12 @@
+library Y {
+    event E() anonymous;
+}
+
+contract D {
+    function test1() external pure returns (bytes32) {
+        return Y.E.selector;
+    }
+
+}
+// ----
+// TypeError 9582: (123-135): Member "selector" not found or not visible after argument-dependent lookup in function ().

test/libsolidity/syntaxTests/events/event_selector_library_declared_outside_but_called_inside_function.sol

@@ -0,0 +1,13 @@
+library Y {
+    event E() anonymous;
+}
+
+contract C {
+    bytes32 s5 = Y.E.selector;
+
+    function test2() view external returns (bytes32) {
+        return s5;
+    }
+}
+// ----
+// TypeError 9582: (70-82): Member "selector" not found or not visible after argument-dependent lookup in function ().

test/libsolidity/syntaxTests/events/event_selector_syntax.sol

@@ -0,0 +1,43 @@
+library L {
+    event E();
+}
+library S {
+    event E(uint);
+}
+library T {
+    event E();
+}
+interface I {
+    event E();
+}
+
+contract D {
+    event F();
+}
+
+contract C is D {
+    function test1() external pure returns (bytes32, bytes32, bytes32) {
+        assert(L.E.selector == T.E.selector);
+        assert(I.E.selector == L.E.selector);
+
+        assert(L.E.selector != S.E.selector);
+        assert(T.E.selector != S.E.selector);
+        assert(I.E.selector != S.E.selector);
+
+        return (L.E.selector, S.E.selector, I.E.selector);
+    }
+
+    bytes32 s1 = L.E.selector;
+    bytes32 s2 = S.E.selector;
+    bytes32 s3 = T.E.selector;
+    bytes32 s4 = I.E.selector;
+
+    function test2() view external returns (bytes32, bytes32, bytes32, bytes32) {
+        return (s1, s2, s3, s4);
+    }
+
+    function test3() pure external returns (bytes32) {
+        return (F.selector);
+    }
+}
+// ----