Mark chainid as view.

Changelog.md

@@ -22,6 +22,7 @@ Breaking Changes:
  * 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: Unary negation can only be used on signed integers, not on unsigned integers.
+ * View Pure Checker: Mark ``chainid`` as view.
 
 Language Features:
  * Super constructors can now be called using the member notation e.g. ``M.C(123)``.

docs/080-breaking-changes.rst

@@ -91,6 +91,8 @@ New Restrictions
 * Remove support for the ``\b``, ``\f``, and ``\v`` escape sequences in code.
   They can still be inserted via hexadecimal escapes, e.g. ``\x08``, ``\x0c``, and ``\x0b``, respectively.
 
+* The ``chainid`` builtin in inline assembly is now considered ``view`` instead of ``pure``.
+
 Interface Changes
 =================
 

libevmasm/SemanticInformation.cpp

@@ -365,6 +365,7 @@ bool SemanticInformation::invalidInPureFunctions(Instruction _instruction)
 	case Instruction::ORIGIN:
 	case Instruction::CALLER:
 	case Instruction::CALLVALUE:
+	case Instruction::CHAINID:
 	case Instruction::GAS:
 	case Instruction::GASPRICE:
 	case Instruction::EXTCODESIZE:

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()) }
     }
 }