Following consensus on: #2580 (review)

This PR phases out the precompiled per final consensus made in #2580
i#
Fix a cfg

serde_derive/src/de.rs

@@ -6,8 +6,6 @@ use proc_macro2::{Literal, Span, TokenStream};
 use quote::{quote, quote_spanned, ToTokens};
 use std::collections::BTreeSet;
 use std::ptr;
-#[cfg(precompiled)]
-use std::sync::atomic::Ordering;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::{parse_quote, Ident, Index, Member};
@@ -301,11 +299,6 @@ fn deserialize_body(cont: &Container, params: &Parameters) -> Fragment {
 
 #[cfg(feature = "deserialize_in_place")]
 fn deserialize_in_place_body(cont: &Container, params: &Parameters) -> Option<Stmts> {
-    #[cfg(precompiled)]
-    if !crate::DESERIALIZE_IN_PLACE.load(Ordering::Relaxed) {
-        return None;
-    }
-
     // Only remote derives have getters, and we do not generate
     // deserialize_in_place for remote derives.
     assert!(!params.has_getter);

serde_derive/src/lib.rs

@@ -66,17 +66,11 @@ extern crate proc_macro2;
 extern crate quote;
 extern crate syn;
 
-#[cfg(not(precompiled))]
 extern crate proc_macro;
-#[cfg(precompiled)]
-extern crate proc_macro2 as proc_macro;
 
 mod internals;
 
 use proc_macro::TokenStream;
-#[cfg(precompiled)]
-use std::sync::atomic::AtomicBool;
-#[cfg(not(precompiled))]
 use syn::parse_macro_input;
 use syn::DeriveInput;
 
@@ -91,20 +85,7 @@ mod pretend;
 mod ser;
 mod this;
 
-#[cfg(precompiled)]
-macro_rules! parse_macro_input {
-    ($tokenstream:ident as $ty:ty) => {
-        match syn::parse2::<$ty>($tokenstream) {
-            Ok(data) => data,
-            Err(err) => return err.to_compile_error(),
-        }
-    };
-}
-
-#[cfg(precompiled)]
-pub static DESERIALIZE_IN_PLACE: AtomicBool = AtomicBool::new(false);
-
-#[cfg_attr(not(precompiled), proc_macro_derive(Serialize, attributes(serde)))]
+#[proc_macro_derive(Serialize, attributes(serde))]
 pub fn derive_serialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);
     ser::expand_derive_serialize(&mut input)
@@ -112,7 +93,7 @@ pub fn derive_serialize(input: TokenStream) -> TokenStream {
         .into()
 }
 
-#[cfg_attr(not(precompiled), proc_macro_derive(Deserialize, attributes(serde)))]
+#[proc_macro_derive(Deserialize, attributes(serde))]
 pub fn derive_deserialize(input: TokenStream) -> TokenStream {
     let mut input = parse_macro_input!(input as DeriveInput);
     de::expand_derive_deserialize(&mut input)