Address review comments

compiler/rustc_span/src/symbol.rs

@@ -127,6 +127,7 @@ symbols! {
         ArgumentV1,
         Arguments,
         C,
+        CString,
         Center,
         Clone,
         Copy,
@@ -261,6 +262,7 @@ symbols! {
         arm_target_feature,
         array,
         arrays,
+        as_ptr,
         as_str,
         asm,
         assert,
@@ -310,6 +312,7 @@ symbols! {
         breakpoint,
         bridge,
         bswap,
+        c_str,
         c_variadic,
         call,
         call_mut,
@@ -477,6 +480,7 @@ symbols! {
         existential_type,
         exp2f32,
         exp2f64,
+        expect,
         expected,
         expf32,
         expf64,
@@ -500,6 +504,7 @@ symbols! {
         fadd_fast,
         fdiv_fast,
         feature,
+        ffi,
         ffi_const,
         ffi_pure,
         ffi_returns_twice,
@@ -1167,6 +1172,7 @@ symbols! {
         unused_qualifications,
         unwind,
         unwind_attributes,
+        unwrap,
         unwrap_or,
         use_extern_macros,
         use_nested_groups,