Release 1.0.45

Pretend remote derives are not dead code

.travis.yml

@@ -5,6 +5,7 @@ cache: cargo
 # run builds for all the trains (and more)
 rust:
   - 1.13.0
+  - 1.15.0
   - stable
   - beta
   - nightly

serde/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde"
-version = "1.0.44" # remember to update html_root_url
+version = "1.0.45" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "A generic serialization/deserialization framework"

serde/src/lib.rs

@@ -79,7 +79,7 @@
 ////////////////////////////////////////////////////////////////////////////////
 
 // Serde types in rustdoc of other crates get linked to here.
-#![doc(html_root_url = "https://docs.rs/serde/1.0.44")]
+#![doc(html_root_url = "https://docs.rs/serde/1.0.45")]
 // Support using Serde without the standard library!
 #![cfg_attr(not(feature = "std"), no_std)]
 // Unstable functionality only if the user asks for it. For tracking and

serde_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_derive"
-version = "1.0.44" # remember to update html_root_url
+version = "1.0.45" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Macros 1.1 implementation of #[derive(Serialize, Deserialize)]"

serde_derive/src/de.rs

@@ -16,6 +16,7 @@ use bound;
 use fragment::{Expr, Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
 use internals::{self, attr};
+use pretend;
 use try;
 
 use std::collections::BTreeSet;
@@ -37,11 +38,13 @@ pub fn expand_derive_deserialize(input: &syn::DeriveInput) -> Result<Tokens, Str
 
     let impl_block = if let Some(remote) = cont.attrs.remote() {
         let vis = &input.vis;
+        let used = pretend::pretend_used(&cont);
         quote! {
             impl #de_impl_generics #ident #ty_generics #where_clause {
                 #vis fn deserialize<__D>(__deserializer: __D) -> _serde::export::Result<#remote #ty_generics, __D::Error>
                     where __D: _serde::Deserializer<#delife>
                 {
+                    #used
                     #body
                 }
             }

serde_derive/src/lib.rs

@@ -22,7 +22,7 @@
 //!
 //! [https://serde.rs/derive.html]: https://serde.rs/derive.html
 
-#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.44")]
+#![doc(html_root_url = "https://docs.rs/serde_derive/1.0.45")]
 #![cfg_attr(
     feature = "cargo-clippy",
     allow(enum_variant_names, redundant_field_names, too_many_arguments, used_underscore_binding)
@@ -49,6 +49,7 @@ mod bound;
 mod fragment;
 
 mod de;
+mod pretend;
 mod ser;
 mod try;
 

serde_derive/src/pretend.rs

@@ -0,0 +1,145 @@
+use proc_macro2::Span;
+use quote::Tokens;
+use syn::Ident;
+
+use internals::ast::{Container, Data, Field, Style};
+
+// Suppress dead_code warnings that would otherwise appear when using a remote
+// derive. Other than this pretend code, a struct annotated with remote derive
+// never has its fields referenced and an enum annotated with remote derive
+// never has its variants constructed.
+//
+//     warning: field is never used: `i`
+//      --> src/main.rs:4:20
+//       |
+//     4 | struct StructDef { i: i32 }
+//       |                    ^^^^^^
+//
+//     warning: variant is never constructed: `V`
+//      --> src/main.rs:8:16
+//       |
+//     8 | enum EnumDef { V }
+//       |                ^
+//
+pub fn pretend_used(cont: &Container) -> Tokens {
+    let pretend_fields = pretend_fields_used(cont);
+    let pretend_variants = pretend_variants_used(cont);
+
+    quote! {
+        #pretend_fields
+        #pretend_variants
+    }
+}
+
+// For structs with named fields, expands to:
+//
+//     match None::<T> {
+//         Some(T { a: ref __v0, b: ref __v1 }) => {}
+//         _ => {}
+//     }
+//
+// For enums, expands to the following but only including struct variants:
+//
+//     match None::<T> {
+//         Some(T::A { a: ref __v0 }) => {}
+//         Some(T::B { b: ref __v0 }) => {}
+//         _ => {}
+//     }
+//
+// The `ref` is important in case the user has written a Drop impl on their
+// type. Rust does not allow destructuring a struct or enum that has a Drop
+// impl.
+fn pretend_fields_used(cont: &Container) -> Tokens {
+    let type_ident = cont.ident;
+    let (_, ty_generics, _) = cont.generics.split_for_impl();
+
+    let patterns = match cont.data {
+        Data::Enum(ref variants) => {
+            variants.iter()
+                .filter_map(|variant| match variant.style {
+                    Style::Struct => {
+                        let variant_ident = variant.ident;
+                        let pat = struct_pattern(&variant.fields);
+                        Some(quote!(#type_ident::#variant_ident #pat))
+                    }
+                    _ => None,
+                })
+                .collect::<Vec<_>>()
+        }
+        Data::Struct(Style::Struct, ref fields) => {
+            let pat = struct_pattern(fields);
+            vec![quote!(#type_ident #pat)]
+        }
+        Data::Struct(_, _) => {
+            return quote!();
+        }
+    };
+
+    quote! {
+        match _serde::export::None::<#type_ident #ty_generics> {
+            #(
+                _serde::export::Some(#patterns) => {}
+            )*
+            _ => {}
+        }
+    }
+}
+
+// Expands to one of these per enum variant:
+//
+//     match None {
+//         Some((__v0, __v1,)) => {
+//             let _ = E::V { a: __v0, b: __v1 };
+//         }
+//         _ => {}
+//     }
+//
+fn pretend_variants_used(cont: &Container) -> Tokens {
+    let variants = match cont.data {
+        Data::Enum(ref variants) => variants,
+        Data::Struct(_, _) => {
+            return quote!();
+        }
+    };
+
+    let type_ident = cont.ident;
+    let (_, ty_generics, _) = cont.generics.split_for_impl();
+    let turbofish = ty_generics.as_turbofish();
+
+    let cases = variants.iter()
+        .map(|variant| {
+            let variant_ident = variant.ident;
+            let ref placeholders = (0..variant.fields.len())
+                .map(|i| Ident::new(&format!("__v{}", i), Span::call_site()))
+                .collect::<Vec<_>>();
+
+            let pat = match variant.style {
+                Style::Struct => {
+                    let names = variant.fields.iter().map(|field| field.ident);
+                    quote!({ #(#names: #placeholders),* })
+                }
+                Style::Tuple | Style::Newtype => {
+                    quote!(( #(#placeholders),* ))
+                }
+                Style::Unit => quote!(),
+            };
+
+            quote! {
+                match _serde::export::None {
+                    _serde::export::Some((#(#placeholders,)*)) => {
+                        let _ = #type_ident::#variant_ident #turbofish #pat;
+                    }
+                    _ => {}
+                }
+            }
+        });
+
+    quote!(#(#cases)*)
+}
+
+fn struct_pattern(fields: &[Field]) -> Tokens {
+    let names = fields.iter().map(|field| field.ident);
+    let placeholders = (0..fields.len())
+        .map(|i| Ident::new(&format!("__v{}", i), Span::call_site()));
+    quote!({ #(#names: ref #placeholders),* })
+}

serde_derive/src/ser.rs

@@ -15,6 +15,7 @@ use bound;
 use fragment::{Fragment, Match, Stmts};
 use internals::ast::{Container, Data, Field, Style, Variant};
 use internals::{attr, Ctxt};
+use pretend;
 use try;
 
 use std::u32;
@@ -33,11 +34,13 @@ pub fn expand_derive_serialize(input: &syn::DeriveInput) -> Result<Tokens, Strin
 
     let impl_block = if let Some(remote) = cont.attrs.remote() {
         let vis = &input.vis;
+        let used = pretend::pretend_used(&cont);
         quote! {
             impl #impl_generics #ident #ty_generics #where_clause {
                 #vis fn serialize<__S>(__self: &#remote #ty_generics, __serializer: __S) -> _serde::export::Result<__S::Ok, __S::Error>
                     where __S: _serde::Serializer
                 {
+                    #used
                     #body
                 }
             }

serde_test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "serde_test"
-version = "1.0.44" # remember to update html_root_url
+version = "1.0.45" # remember to update html_root_url
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 license = "MIT/Apache-2.0"
 description = "Token De/Serializer for testing De/Serialize implementations"

serde_test/src/lib.rs

@@ -155,7 +155,7 @@
 //! # }
 //! ```
 
-#![doc(html_root_url = "https://docs.rs/serde_test/1.0.44")]
+#![doc(html_root_url = "https://docs.rs/serde_test/1.0.45")]
 #![cfg_attr(feature = "cargo-clippy", deny(clippy, clippy_pedantic))]
 // Whitelisted clippy lints
 #![cfg_attr(feature = "cargo-clippy", allow(float_cmp))]

test_suite/tests/test_gen.rs

@@ -333,9 +333,7 @@ fn test_gen() {
     #[derive(Serialize, Deserialize)]
     #[serde(untagged, remote = "Or")]
     enum OrDef<A, B> {
-        #[allow(dead_code)]
         A(A),
-        #[allow(dead_code)]
         B(B),
     }
 

test_suite/tests/test_remote.rs

@@ -160,10 +160,8 @@ struct StructPrivDef {
 #[derive(Serialize, Deserialize)]
 #[serde(remote = "remote::StructPub")]
 struct StructPubDef {
-    #[allow(dead_code)]
     a: u8,
 
-    #[allow(dead_code)]
     #[serde(with = "UnitDef")]
     b: remote::Unit,
 }

travis.sh

@@ -87,4 +87,10 @@ else
     channel build --no-default-features
     cd "$DIR/serde_test"
     channel build
+
+    CHANNEL=1.15.0
+    cd "$DIR"
+    cargo clean
+    cd "$DIR/serde_derive"
+    channel build
 fi