Rollup merge of #35728 - petrochenkov:empderive, r=manishearth

Fix #[derive] for empty tuple structs/variants

This was missing from https://github.com/rust-lang/rust/pull/35138

5 files changed, 36 insertions, 30 deletions

diff --git a/src/libsyntax_ext/deriving/cmp/ord.rs b/src/libsyntax_ext/deriving/cmp/ord.rs
index 8ae77e79310..31194b04fa6 100644
--- a/src/libsyntax_ext/deriving/cmp/ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/ord.rs
@@ -104,7 +104,7 @@ pub fn cs_cmp(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
         };
 
         let eq_arm = cx.arm(span,
-                            vec![cx.pat_enum(span, equals_path.clone(), vec![])],
+                            vec![cx.pat_path(span, equals_path.clone())],
                             old);
         let neq_arm = cx.arm(span,
                              vec![cx.pat_ident(span, test_id)],
diff --git a/src/libsyntax_ext/deriving/cmp/partial_ord.rs b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
index 10a9738742e..9e9b2f02062 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
@@ -165,7 +165,7 @@ pub fn cs_partial_cmp(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<
         };
 
         let eq_arm = cx.arm(span,
-                            vec![cx.pat_some(span, cx.pat_enum(span, ordering.clone(), vec![]))],
+                            vec![cx.pat_some(span, cx.pat_path(span, ordering.clone()))],
                             old);
         let neq_arm = cx.arm(span,
                              vec![cx.pat_ident(span, test_id)],
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index 9a332227053..f395f7bd0c4 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -110,7 +110,7 @@ fn decodable_substructure(cx: &mut ExtCtxt,
     return match *substr.fields {
         StaticStruct(_, ref summary) => {
             let nfields = match *summary {
-                Unnamed(ref fields) => fields.len(),
+                Unnamed(ref fields, _) => fields.len(),
                 Named(ref fields) => fields.len(),
             };
             let read_struct_field = cx.ident_of("read_struct_field");
@@ -193,9 +193,9 @@ fn decode_static_fields<F>(cx: &mut ExtCtxt,
     where F: FnMut(&mut ExtCtxt, Span, InternedString, usize) -> P<Expr>
 {
     match *fields {
-        Unnamed(ref fields) => {
+        Unnamed(ref fields, is_tuple) => {
             let path_expr = cx.expr_path(outer_pat_path);
-            if fields.is_empty() {
+            if !is_tuple {
                 path_expr
             } else {
                 let fields = fields.iter()
diff --git a/src/libsyntax_ext/deriving/default.rs b/src/libsyntax_ext/deriving/default.rs
index 9df3db938b1..449c1ff066b 100644
--- a/src/libsyntax_ext/deriving/default.rs
+++ b/src/libsyntax_ext/deriving/default.rs
@@ -57,8 +57,8 @@ fn default_substructure(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructur
     return match *substr.fields {
         StaticStruct(_, ref summary) => {
             match *summary {
-                Unnamed(ref fields) => {
-                    if fields.is_empty() {
+                Unnamed(ref fields, is_tuple) => {
+                    if !is_tuple {
                         cx.expr_ident(trait_span, substr.type_ident)
                     } else {
                         let exprs = fields.iter().map(|sp| default_call(*sp)).collect();
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 5960e4546b1..03282653d36 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -294,8 +294,8 @@ pub struct FieldInfo<'a> {
 
 /// Fields for a static method
 pub enum StaticFields {
-    /// Tuple structs/enum variants like this.
-    Unnamed(Vec<Span>),
+    /// Tuple and unit structs/enum variants like this.
+    Unnamed(Vec<Span>, bool /*is tuple*/),
     /// Normal structs/struct variants.
     Named(Vec<(Ident, Span)>),
 }
@@ -1472,7 +1472,7 @@ impl<'a> TraitDef<'a> {
             (_, false) => Named(named_idents),
             // empty structs
             _ if struct_def.is_struct() => Named(named_idents),
-            _ => Unnamed(just_spans),
+            _ => Unnamed(just_spans, struct_def.is_tuple()),
         }
     }
 
@@ -1512,26 +1512,32 @@ impl<'a> TraitDef<'a> {
         }
 
         let subpats = self.create_subpatterns(cx, paths, mutbl);
-        let pattern = if struct_def.is_struct() {
-            let field_pats = subpats.into_iter()
-                .zip(&ident_exprs)
-                .map(|(pat, &(sp, ident, _, _))| {
-                    if ident.is_none() {
-                        cx.span_bug(sp, "a braced struct with unnamed fields in `derive`");
-                    }
-                    codemap::Spanned {
-                        span: pat.span,
-                        node: ast::FieldPat {
-                            ident: ident.unwrap(),
-                            pat: pat,
-                            is_shorthand: false,
-                        },
-                    }
-                })
-                .collect();
-            cx.pat_struct(self.span, struct_path, field_pats)
-        } else {
-            cx.pat_enum(self.span, struct_path, subpats)
+        let pattern = match *struct_def {
+            VariantData::Struct(..) => {
+                let field_pats = subpats.into_iter()
+                    .zip(&ident_exprs)
+                    .map(|(pat, &(sp, ident, _, _))| {
+                        if ident.is_none() {
+                            cx.span_bug(sp, "a braced struct with unnamed fields in `derive`");
+                        }
+                        codemap::Spanned {
+                            span: pat.span,
+                            node: ast::FieldPat {
+                                ident: ident.unwrap(),
+                                pat: pat,
+                                is_shorthand: false,
+                            },
+                        }
+                    })
+                    .collect();
+                cx.pat_struct(self.span, struct_path, field_pats)
+            }
+            VariantData::Tuple(..) => {
+                cx.pat_tuple_struct(self.span, struct_path, subpats)
+            }
+            VariantData::Unit(..) => {
+                cx.pat_path(self.span, struct_path)
+            }
         };
 
         (pattern, ident_exprs)