Merge pull request #174 from nikomatsakis/underscore-impls

use underscore impls where we can

Author: nikomatsakis

crates/formality-macros/src/cast.rs

@@ -6,7 +6,9 @@ use synstructure::VariantInfo;
 
 use crate::attrs::has_isa_attr;
 
-pub(crate) fn upcast_impls(s: synstructure::Structure) -> Vec<TokenStream> {
+pub(crate) fn upcast_impls(mut s: synstructure::Structure) -> Vec<TokenStream> {
+    s.underscore_const(true);
+
     let num_variants = s.variants().len();
     s.variants()
         .iter()
@@ -74,7 +76,9 @@ fn upcast_to_variant(s: &synstructure::Structure, v: &VariantInfo) -> TokenStrea
     })
 }
 
-pub(crate) fn downcast_impls(s: synstructure::Structure) -> Vec<TokenStream> {
+pub(crate) fn downcast_impls(mut s: synstructure::Structure) -> Vec<TokenStream> {
+    s.underscore_const(true);
+
     let num_variants = s.variants().len();
     s.variants()
         .iter()

crates/formality-macros/src/debug.rs

@@ -13,9 +13,11 @@ use crate::{
 /// Derive the `Parse` impl, using an optional grammar supplied "from the outside".
 /// This is used by the `#[term(G)]` macro, which supplies the grammar `G`.
 pub(crate) fn derive_debug_with_spec(
-    s: synstructure::Structure,
+    mut s: synstructure::Structure,
     external_spec: Option<&FormalitySpec>,
 ) -> TokenStream {
+    s.underscore_const(true);
+
     if let syn::Data::Union(v) = &s.ast().data {
         return syn::Error::new(v.union_token.span, "unions are not supported")
             .into_compile_error();

crates/formality-macros/src/parse.rs

@@ -15,9 +15,11 @@ use crate::{
 /// Derive the `Parse` impl, using an optional grammar supplied "from the outside".
 /// This is used by the `#[term(G)]` macro, which supplies the grammar `G`.
 pub(crate) fn derive_parse_with_spec(
-    s: synstructure::Structure,
+    mut s: synstructure::Structure,
     external_spec: Option<&FormalitySpec>,
 ) -> syn::Result<TokenStream> {
+    s.underscore_const(true);
+
     if let syn::Data::Union(v) = &s.ast().data {
         return Err(syn::Error::new(
             v.union_token.span,