Tests for basefee as identifier in inline assembly

Also added basefee to `EVMVersion::hasOpcode(...)`

liblangutil/EVMVersion.cpp

@@ -46,8 +46,9 @@ bool EVMVersion::hasOpcode(Instruction _opcode) const
 		return hasChainID();
 	case Instruction::SELFBALANCE:
 		return hasSelfBalance();
+	case Instruction::BASEFEE:
+		return hasBaseFee();
 	default:
 		return true;
 	}
 }
-

scripts/test_antlr_grammar.sh

@@ -118,7 +118,9 @@ done < <(
       grep -v -E 'literals/.*_direction_override.*.sol' |
       # Skipping a test with "revert E;" because ANTLR cannot distinguish it from
       # a variable declaration.
-      grep -v -E 'revertStatement/non_called.sol'
+      grep -v -E 'revertStatement/non_called.sol' |
+      # Skipping a test with "let basefee := ..."
+      grep -v -E 'inlineAssembly/basefee_berlin_function.sol'
 )
 
 YUL_FILES=()

test/libsolidity/semanticTests/inlineAssembly/basefee_berlin_function.sol

@@ -0,0 +1,22 @@
+contract C {
+    function f() public view returns (uint ret) {
+        assembly {
+            let basefee := sload(0)
+            ret := basefee
+        }
+    }
+    function g() public pure returns (uint ret) {
+        assembly {
+            function basefee() -> r {
+                r := 1000
+            }
+            ret := basefee()
+        }
+    }
+}
+// ====
+// compileViaYul: also
+// EVMVersion: <=berlin
+// ----
+// f() -> 0
+// g() -> 1000

test/libsolidity/syntaxTests/inlineAssembly/basefee_reserved_london.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() public view returns (uint ret) {
+        assembly {
+            let basefee := sload(0)
+            ret := basefee
+        }
+    }
+}
+// ====
+// EVMVersion: =london
+// ----
+// ParserError 5568: (98-105): Cannot use builtin function name "basefee" as identifier name.