Validate immutable variables

test/libsolidity/syntaxTests/viewPureChecker/immutable.sol

@@ -1,8 +1,8 @@
 contract B {
-    uint immutable x;
+    uint immutable x = 1;
     function f() public pure returns (uint) {
         return x;
     }
 }
 // ----
-// TypeError: (96-97): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".
+// TypeError: (100-101): Function declared as pure, but this expression (potentially) reads from the environment or state and thus requires "view".