Implemented block.basefee in Solidilty and basefee() in Yul.

Also added basefee to Yul grammar.

Author: hrkrshnn

docs/grammar/SolidityLexer.g4

@@ -284,7 +284,8 @@ YulEVMBuiltin:
 	| 'returndatacopy' | 'extcodehash' | 'create' | 'create2' | 'call' | 'callcode'
 	| 'delegatecall' | 'staticcall' | 'return' | 'revert' | 'selfdestruct' | 'invalid'
 	| 'log0' | 'log1' | 'log2' | 'log3' | 'log4' | 'chainid' | 'origin' | 'gasprice'
-	| 'blockhash' | 'coinbase' | 'timestamp' | 'number' | 'difficulty' | 'gaslimit';
+	| 'blockhash' | 'coinbase' | 'timestamp' | 'number' | 'difficulty' | 'gaslimit'
+	| 'basefee';
 
 YulLBrace: '{' -> pushMode(YulMode);
 YulRBrace: '}' -> popMode;

libsolidity/analysis/TypeChecker.cpp

@@ -2947,6 +2947,12 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
 				_memberAccess.location(),
 				"\"chainid\" is not supported by the VM version."
 			);
+		else if (magicType->kind() == MagicType::Kind::Block && memberName == "basefee" && !m_evmVersion.hasBaseFee())
+			m_errorReporter.typeError(
+				5921_error,
+				_memberAccess.location(),
+				"\"basefee\" is not supported by the VM version."
+			);
 	}
 
 	if (

libsolidity/ast/Types.cpp

@@ -3892,7 +3892,8 @@ MemberList::MemberMap MagicType::nativeMembers(ASTNode const*) const
 			{"difficulty", TypeProvider::uint256()},
 			{"number", TypeProvider::uint256()},
 			{"gaslimit", TypeProvider::uint256()},
-			{"chainid", TypeProvider::uint256()}
+			{"chainid", TypeProvider::uint256()},
+			{"basefee", TypeProvider::uint256()}
 		});
 	case Kind::Message:
 		return MemberList::MemberMap({

libsolidity/codegen/ExpressionCompiler.cpp

@@ -1731,6 +1731,8 @@ bool ExpressionCompiler::visit(MemberAccess const& _memberAccess)
 			m_context << Instruction::GASPRICE;
 		else if (member == "chainid")
 			m_context << Instruction::CHAINID;
+		else if (member == "basefee")
+			m_context << Instruction::BASEFEE;
 		else if (member == "data")
 			m_context << u256(0) << Instruction::CALLDATASIZE;
 		else if (member == "sig")

libsolidity/codegen/ir/IRGeneratorForStatements.cpp

@@ -1733,6 +1733,8 @@ void IRGeneratorForStatements::endVisit(MemberAccess const& _memberAccess)
 			define(_memberAccess) << "gasprice()\n";
 		else if (member == "chainid")
 			define(_memberAccess) << "chainid()\n";
+		else if (member == "basefee")
+			define(_memberAccess) << "basefee()\n";
 		else if (member == "data")
 		{
 			IRVariable var(_memberAccess);

libyul/AsmAnalysis.cpp

@@ -695,6 +695,8 @@ bool AsmAnalyzer::validateInstructions(evmasm::Instruction _instr, SourceLocatio
 		errorForVM(1561_error, "only available for Istanbul-compatible");
 	else if (_instr == evmasm::Instruction::SELFBALANCE && !m_evmVersion.hasSelfBalance())
 		errorForVM(7721_error, "only available for Istanbul-compatible");
+	else if (_instr == evmasm::Instruction::BASEFEE && !m_evmVersion.hasBaseFee())
+		errorForVM(5430_error, "only available for London-compatible");
 	else if (_instr == evmasm::Instruction::PC)
 		m_errorReporter.error(
 			2450_error,