Introduce block.chainid

Changelog.md

@@ -22,6 +22,7 @@ Breaking Changes:
  * Type System: Explicit conversions between two types are disallowed if it changes more than one of sign, width or kind at the same time.
  * Type System: Explicit conversions from literals to enums are only allowed if the value fits in the enum.
  * Type System: Explicit conversions from literals to integer type is as strict as implicit conversions.
+ * Type System: Introduce ``block.chainid`` for retrieving the current chain id.
  * Type System: Support ``address(...).codehash`` to retrieve the codehash of an account.
  * Type System: Unary negation can only be used on signed integers, not on unsigned integers.
  * View Pure Checker: Mark ``chainid`` as view.

docs/cheatsheet.rst

@@ -82,6 +82,7 @@ Global Variables
   the given arguments starting from the second and prepends the given four-byte selector
 - ``abi.encodeWithSignature(string memory signature, ...) returns (bytes memory)``: Equivalent
   to ``abi.encodeWithSelector(bytes4(keccak256(bytes(signature)), ...)```
+- ``block.chainid`` (``uint``): current chain id
 - ``block.coinbase`` (``address payable``): current block miner's address
 - ``block.difficulty`` (``uint``): current block difficulty
 - ``block.gaslimit`` (``uint``): current block gaslimit

docs/units-and-global-variables.rst

@@ -69,6 +69,7 @@ Block and Transaction Properties
 --------------------------------
 
 - ``blockhash(uint blockNumber) returns (bytes32)``: hash of the given block - only works for 256 most recent, excluding current, blocks
+- ``block.chainid`` (``uint``): current chain id
 - ``block.coinbase`` (``address payable``): current block miner's address
 - ``block.difficulty`` (``uint``): current block difficulty
 - ``block.gaslimit`` (``uint``): current block gaslimit

libsolidity/analysis/TypeChecker.cpp

@@ -2922,6 +2922,12 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
 			(memberName == "min" ||	memberName == "max")
 		)
 			annotation.isPure = true;
+		else if (magicType->kind() == MagicType::Kind::Block && memberName == "chainid" && !m_evmVersion.hasChainID())
+			m_errorReporter.typeError(
+				3081_error,
+				_memberAccess.location(),
+				"\"chainid\" is not supported by the VM version."
+			);
 	}
 
 	if (

libsolidity/analysis/ViewPureChecker.cpp

@@ -368,7 +368,6 @@ void ViewPureChecker::endVisit(MemberAccess const& _memberAccess)
 			{MagicType::Kind::ABI, "encodePacked"},
 			{MagicType::Kind::ABI, "encodeWithSelector"},
 			{MagicType::Kind::ABI, "encodeWithSignature"},
-			{MagicType::Kind::Block, "blockhash"},
 			{MagicType::Kind::Message, "data"},
 			{MagicType::Kind::Message, "sig"},
 			{MagicType::Kind::MetaType, "creationCode"},

libsolidity/ast/Types.cpp

@@ -3825,7 +3825,8 @@ MemberList::MemberMap MagicType::nativeMembers(ASTNode const*) const
 			{"blockhash", TypeProvider::function(strings{"uint"}, strings{"bytes32"}, FunctionType::Kind::BlockHash, false, StateMutability::View)},
 			{"difficulty", TypeProvider::uint256()},
 			{"number", TypeProvider::uint256()},
-			{"gaslimit", TypeProvider::uint256()}
+			{"gaslimit", TypeProvider::uint256()},
+			{"chainid", TypeProvider::uint256()}
 		});
 	case Kind::Message:
 		return MemberList::MemberMap({

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1576,6 +1576,8 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 			m_context << Instruction::ORIGIN;
 		else if (member == "gasprice")
 			m_context << Instruction::GASPRICE;
+		else if (member == "chainid")
+			m_context << Instruction::CHAINID;
 		else if (member == "data")
 			m_context << u256(0) << Instruction::CALLDATASIZE;
 		else if (member == "sig")

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -1688,6 +1688,8 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 			define(_memberAccess) << "origin()\n";
 		else if (member == "gasprice")
 			define(_memberAccess) << "gasprice()\n";
+		else if (member == "chainid")
+			define(_memberAccess) << "chainid()\n";
 		else if (member == "data")
 		{
 			IRVariable var(_memberAccess);

test/libsolidity/semanticTests/state/block_chainid.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() public returns (uint) {
+        return block.chainid;
+    }
+}
+// ====
+// EVMVersion: >=istanbul
+// compileViaYul: also
+// ----
+// f() -> 1
+// f() -> 1
+// f() -> 1

test/libsolidity/syntaxTests/types/magic_block.sol

@@ -11,6 +11,11 @@ contract C {
     function i() public view returns (uint) {
         return block.timestamp;
     }
+    function j() public view returns (uint) {
+        return block.chainid;
+    }
 }
 // ====
 // EVMVersion: <istanbul
+// ----
+// TypeError 3081: (420-433): "chainid" is not supported by the VM version.

test/libsolidity/syntaxTests/types/magic_block_istanbul.sol

@@ -11,6 +11,9 @@ contract C {
     function i() public view returns (uint) {
         return block.timestamp;
     }
+    function j() public view returns (uint) {
+        return block.chainid;
+    }
 }
 // ====
 // EVMVersion: >=istanbul

test/libsolidity/syntaxTests/viewPureChecker/assembly_chainid_not_pure.sol

@@ -2,8 +2,12 @@ contract C {
     function f() public pure {
         assembly { pop(chainid()) }
     }
+    function g() public pure returns (uint) {
+        return block.chainid;
+    }
 }
 // ====
 // EVMVersion: >=istanbul
 // ----
 // TypeError 2527: (67-76): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
+// TypeError 2527: (147-160): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".

test/libsolidity/syntaxTests/viewPureChecker/assembly_istanbul.sol

@@ -2,6 +2,9 @@ contract C {
     function f() public view {
         assembly { pop(chainid()) }
     }
+    function g() public view returns (uint) {
+        return block.chainid;
+    }
 }
 // ====
 // EVMVersion: >=istanbul