Rollup merge of #104391 - nnethercote:deriving-cleanups, r=jackh726

Deriving cleanups

Fixing some minor problems `@RalfJung` found in #99046.

r? `@RalfJung`

compiler/rustc_ast/src/ast.rs

@@ -392,15 +392,7 @@ pub struct Generics {
 impl Default for Generics {
     /// Creates an instance of `Generics`.
     fn default() -> Generics {
-        Generics {
-            params: Vec::new(),
-            where_clause: WhereClause {
-                has_where_token: false,
-                predicates: Vec::new(),
-                span: DUMMY_SP,
-            },
-            span: DUMMY_SP,
-        }
+        Generics { params: Vec::new(), where_clause: Default::default(), span: DUMMY_SP }
     }
 }
 
@@ -415,6 +407,12 @@ pub struct WhereClause {
     pub span: Span,
 }
 
+impl Default for WhereClause {
+    fn default() -> WhereClause {
+        WhereClause { has_where_token: false, predicates: Vec::new(), span: DUMMY_SP }
+    }
+}
+
 /// A single predicate in a where-clause.
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum WherePredicate {

compiler/rustc_builtin_macros/src/deriving/bounds.rs

@@ -1,4 +1,3 @@
-use crate::deriving::generic::ty::*;
 use crate::deriving::generic::*;
 use crate::deriving::path_std;
 
@@ -19,7 +18,6 @@ pub fn expand_deriving_copy(
         path: path_std!(marker::Copy),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: true,
         methods: Vec::new(),
         associated_types: Vec::new(),

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -75,7 +75,6 @@ pub fn expand_deriving_clone(
         path: path_std!(clone::Clone),
         skip_path_as_bound: false,
         additional_bounds: bounds,
-        generics: Bounds::empty(),
         supports_unions: true,
         methods: vec![MethodDef {
             name: sym::clone,

compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs

@@ -28,7 +28,6 @@ pub fn expand_deriving_eq(
         path: path_std!(cmp::Eq),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: true,
         methods: vec![MethodDef {
             name: sym::assert_receiver_is_total_eq,

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -22,7 +22,6 @@ pub fn expand_deriving_ord(
         path: path_std!(cmp::Ord),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![MethodDef {
             name: sym::cmp,

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -86,7 +86,6 @@ pub fn expand_deriving_partial_eq(
         path: path_std!(cmp::PartialEq),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods,
         associated_types: Vec::new(),

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -40,7 +40,6 @@ pub fn expand_deriving_partial_ord(
         path: path_std!(cmp::PartialOrd),
         skip_path_as_bound: false,
         additional_bounds: vec![],
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![partial_cmp_def],
         associated_types: Vec::new(),

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -23,7 +23,6 @@ pub fn expand_deriving_debug(
         path: path_std!(fmt::Debug),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![MethodDef {
             name: sym::fmt,

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -26,7 +26,6 @@ pub fn expand_deriving_rustc_decodable(
         path: Path::new_(vec![krate, sym::Decodable], vec![], PathKind::Global),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![MethodDef {
             name: sym::decode,

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -27,7 +27,6 @@ pub fn expand_deriving_default(
         path: Path::new(vec![kw::Default, sym::Default]),
         skip_path_as_bound: has_a_default_variant(item),
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![MethodDef {
             name: kw::Default,

compiler/rustc_builtin_macros/src/deriving/encodable.rs

@@ -110,7 +110,6 @@ pub fn expand_deriving_rustc_encodable(
         path: Path::new_(vec![krate, sym::Encodable], vec![], PathKind::Global),
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![MethodDef {
             name: sym::encode,

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -195,9 +195,6 @@ pub struct TraitDef<'a> {
     /// other than the current trait
     pub additional_bounds: Vec<Ty>,
 
-    /// Any extra lifetimes and/or bounds, e.g., `D: serialize::Decoder`
-    pub generics: Bounds,
-
     /// Can this trait be derived for unions?
     pub supports_unions: bool,
 
@@ -583,14 +580,16 @@ impl<'a> TraitDef<'a> {
             })
         });
 
-        let Generics { mut params, mut where_clause, .. } =
-            self.generics.to_generics(cx, self.span, type_ident, generics);
+        let mut where_clause = ast::WhereClause::default();
         where_clause.span = generics.where_clause.span;
         let ctxt = self.span.ctxt();
         let span = generics.span.with_ctxt(ctxt);
 
         // Create the generic parameters
-        params.extend(generics.params.iter().map(|param| match &param.kind {
+        let params: Vec<_> = generics
+            .params
+            .iter()
+            .map(|param| match &param.kind {
                 GenericParamKind::Lifetime { .. } => param.clone(),
                 GenericParamKind::Type { .. } => {
                     // I don't think this can be moved out of the loop, since
@@ -622,7 +621,8 @@ impl<'a> TraitDef<'a> {
                     param_clone.kind = const_nodefault_kind;
                     param_clone
                 }
-        }));
+            })
+            .collect();
 
         // and similarly for where clauses
         where_clause.predicates.extend(generics.where_clause.predicates.iter().map(|clause| {
@@ -1062,18 +1062,15 @@ impl<'a> MethodDef<'a> {
                 trait_.create_struct_field_access_fields(cx, selflike_args, struct_def, true);
             mk_body(cx, selflike_fields)
         } else {
-            // Neither packed nor copy. Need to use ref patterns.
+            // Packed and not copy. Need to use ref patterns.
             let prefixes: Vec<_> =
                 (0..selflike_args.len()).map(|i| format!("__self_{}", i)).collect();
-            let addr_of = always_copy;
-            let selflike_fields =
-                trait_.create_struct_pattern_fields(cx, struct_def, &prefixes, addr_of);
+            let selflike_fields = trait_.create_struct_pattern_fields(cx, struct_def, &prefixes);
             let mut body = mk_body(cx, selflike_fields);
 
             let struct_path = cx.path(span, vec![Ident::new(kw::SelfUpper, type_ident.span)]);
-            let by_ref = ByRef::from(is_packed && !always_copy);
             let patterns =
-                trait_.create_struct_patterns(cx, struct_path, struct_def, &prefixes, by_ref);
+                trait_.create_struct_patterns(cx, struct_path, struct_def, &prefixes, ByRef::Yes);
 
             // Do the let-destructuring.
             let mut stmts: Vec<_> = iter::zip(selflike_args, patterns)
@@ -1254,9 +1251,7 @@ impl<'a> MethodDef<'a> {
                 // A single arm has form (&VariantK, &VariantK, ...) => BodyK
                 // (see "Final wrinkle" note below for why.)
 
-                let addr_of = false; // because enums can't be repr(packed)
-                let fields =
-                    trait_.create_struct_pattern_fields(cx, &variant.data, &prefixes, addr_of);
+                let fields = trait_.create_struct_pattern_fields(cx, &variant.data, &prefixes);
 
                 let sp = variant.span.with_ctxt(trait_.span.ctxt());
                 let variant_path = cx.path(sp, vec![type_ident, variant.ident]);
@@ -1519,15 +1514,13 @@ impl<'a> TraitDef<'a> {
         cx: &mut ExtCtxt<'_>,
         struct_def: &'a VariantData,
         prefixes: &[String],
-        addr_of: bool,
     ) -> Vec<FieldInfo> {
         self.create_fields(struct_def, |i, _struct_field, sp| {
             prefixes
                 .iter()
                 .map(|prefix| {
                     let ident = self.mk_pattern_ident(prefix, i);
-                    let expr = cx.expr_path(cx.path_ident(sp, ident));
-                    if addr_of { cx.expr_addr_of(sp, expr) } else { expr }
+                    cx.expr_path(cx.path_ident(sp, ident))
                 })
                 .collect()
         })

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -25,7 +25,6 @@ pub fn expand_deriving_hash(
         path,
         skip_path_as_bound: false,
         additional_bounds: Vec::new(),
-        generics: Bounds::empty(),
         supports_unions: false,
         methods: vec![MethodDef {
             name: sym::hash,