Work around deprecation of str::trim_left_matches

serde_derive/src/de.rs

@@ -5,11 +5,11 @@ use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
 
 use bound;
+use dummy;
 use fragment::{Expr, Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
 use internals::{attr, Ctxt, Derive};
 use pretend;
-use try;
 
 use std::collections::BTreeSet;
 
@@ -25,11 +25,6 @@ pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<TokenStream
     let ident = &cont.ident;
     let params = Parameters::new(&cont);
     let (de_impl_generics, _, ty_generics, where_clause) = split_with_de_lifetime(&params);
-    let suffix = ident.to_string().trim_left_matches("r#").to_owned();
-    let dummy_const = Ident::new(
-        &format!("_IMPL_DESERIALIZE_FOR_{}", suffix),
-        Span::call_site(),
-    );
     let body = Stmts(deserialize_body(&cont, &params));
     let delife = params.borrowed.de_lifetime();
 
@@ -65,19 +60,7 @@ pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<TokenStream
         }
     };
 
-    let try_replacement = try::replacement();
+    Ok(dummy::wrap_in_const("DESERIALIZE", ident, impl_block))
-    let generated = quote! {
-        #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
-        const #dummy_const: () = {
-            #[allow(unknown_lints)]
-            #[cfg_attr(feature = "cargo-clippy", allow(useless_attribute))]
-            #[allow(rust_2018_idioms)]
-            extern crate serde as _serde;
-            #try_replacement
-            #impl_block
-        };
-    };
-    Ok(generated)
 }
 
 fn precondition(cx: &Ctxt, cont: &Container) {

serde_derive/src/dummy.rs

@@ -0,0 +1,32 @@
+use proc_macro2::{Ident, Span, TokenStream};
+
+use try;
+
+pub fn wrap_in_const(trait_: &str, ty: &Ident, code: TokenStream) -> TokenStream {
+    let try_replacement = try::replacement();
+
+    let dummy_const = Ident::new(
+        &format!("_IMPL_{}_FOR_{}", trait_, unraw(ty)),
+        Span::call_site(),
+    );
+
+    quote! {
+        #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
+        const #dummy_const: () = {
+            #[allow(unknown_lints)]
+            #[cfg_attr(feature = "cargo-clippy", allow(useless_attribute))]
+            #[allow(rust_2018_idioms)]
+            extern crate serde as _serde;
+            #try_replacement
+            #code
+        };
+    }
+}
+
+#[allow(deprecated)]
+fn unraw(ident: &Ident) -> String {
+    // str::trim_start_matches was added in 1.30, trim_left_matches deprecated
+    // in 1.33. We currently support rustc back to 1.15 so we need to continue
+    // to use the deprecated one.
+    ident.to_string().trim_left_matches("r#").to_owned()
+}

serde_derive/src/internals/attr.rs

@@ -95,7 +95,11 @@ pub struct Name {
     deserialize: String,
 }
 
+#[allow(deprecated)]
 fn unraw(ident: &Ident) -> String {
+    // str::trim_start_matches was added in 1.30, trim_left_matches deprecated
+    // in 1.33. We currently support rustc back to 1.15 so we need to continue
+    // to use the deprecated one.
     ident.to_string().trim_left_matches("r#").to_owned()
 }
 

serde_derive/src/lib.rs

@@ -69,6 +69,7 @@ mod bound;
 mod fragment;
 
 mod de;
+mod dummy;
 mod pretend;
 mod ser;
 mod try;

serde_derive/src/ser.rs

@@ -3,11 +3,11 @@ use syn::spanned::Spanned;
 use syn::{self, Ident, Index, Member};
 
 use bound;
+use dummy;
 use fragment::{Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
 use internals::{attr, Ctxt, Derive};
 use pretend;
-use try;
 
 pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<TokenStream, Vec<syn::Error>> {
     let ctxt = Ctxt::new();
@@ -21,11 +21,6 @@ pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<TokenStream,
     let ident = &cont.ident;
     let params = Parameters::new(&cont);
     let (impl_generics, ty_generics, where_clause) = params.generics.split_for_impl();
-    let suffix = ident.to_string().trim_left_matches("r#").to_owned();
-    let dummy_const = Ident::new(
-        &format!("_IMPL_SERIALIZE_FOR_{}", suffix),
-        Span::call_site(),
-    );
     let body = Stmts(serialize_body(&cont, &params));
 
     let impl_block = if let Some(remote) = cont.attrs.remote() {
@@ -56,19 +51,7 @@ pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<TokenStream,
         }
     };
 
-    let try_replacement = try::replacement();
+    Ok(dummy::wrap_in_const("SERIALIZE", ident, impl_block))
-    let generated = quote! {
-        #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
-        const #dummy_const: () = {
-            #[allow(unknown_lints)]
-            #[cfg_attr(feature = "cargo-clippy", allow(useless_attribute))]
-            #[allow(rust_2018_idioms)]
-            extern crate serde as _serde;
-            #try_replacement
-            #impl_block
-        };
-    };
-    Ok(generated)
 }
 
 fn precondition(cx: &Ctxt, cont: &Container) {