Merge pull request #10550 from ethereum/chainIdView

[BREAKING] Mark chainid as view.

test/libsolidity/syntaxTests/inlineAssembly/evm_istanbul.sol

@@ -1,5 +1,5 @@
 contract C {
-    function f() pure external returns (uint id) {
+    function f() view external returns (uint id) {
         assembly {
             id := chainid()
         }

test/libsolidity/syntaxTests/viewPureChecker/assembly_chainid_not_pure.sol

@@ -0,0 +1,9 @@
+contract C {
+    function f() public pure {
+        assembly { pop(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".

test/libsolidity/syntaxTests/viewPureChecker/assembly_istanbul.sol

@@ -1,5 +1,5 @@
 contract C {
-    function f() public pure {
+    function f() public view {
         assembly { pop(chainid()) }
     }
 }