Introduce block.chainid

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