Add trivial_bounds feature to enable Debug impl

multi_index_map/Cargo.toml

@@ -29,3 +29,6 @@ criterion = "0.5.0"
 [[bench]]
 name = "performance"
 harness = false
+
+[features]
+trivial_bounds = ["multi_index_map_derive/trivial_bounds"]

multi_index_map/tests/debug.rs

@@ -0,0 +1,33 @@
+#![cfg_attr(feature = "trivial_bounds", feature(trivial_bounds))]
+#![cfg(feature = "trivial_bounds")]
+use multi_index_map::MultiIndexMap;
+
+#[derive(Hash, PartialEq, Eq, Clone, Debug)]
+struct TestNonPrimitiveType(u64);
+
+#[derive(MultiIndexMap, Clone, Debug)]
+struct TestElement {
+    #[multi_index(hashed_unique)]
+    field1: TestNonPrimitiveType,
+    field2: String,
+}
+
+#[test]
+fn should_compile() {
+    let mut map = MultiIndexTestElementMap::default();
+
+    // check that formatting produces non empty strings
+    assert!(!format!("{:?}", map._field1_index).is_empty());
+    assert!(!format!("{:?}", map._store).is_empty());
+    assert!(!format!("{:?}", map).is_empty());
+
+    let elem1 = TestElement {
+        field1: TestNonPrimitiveType(42),
+        field2: "ElementOne".to_string(),
+    };
+    map.insert(elem1);
+
+    let msg = format!("{:?}", map);
+    // check if stored field 1 is present in debug output
+    assert!(msg.contains("42"));
+}

multi_index_map/tests/get_and_modify_mut.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "trivial_bounds", feature(trivial_bounds))]
+
 use multi_index_map::MultiIndexMap;
 
 #[derive(Hash, PartialEq, Eq, Clone)]

multi_index_map/tests/hashed_unique.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "trivial_bounds", feature(trivial_bounds))]
+
 use multi_index_map::MultiIndexMap;
 
 #[derive(Hash, PartialEq, Eq, Clone)]

multi_index_map/tests/mixed_non_unique.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "trivial_bounds", feature(trivial_bounds))]
+
 use multi_index_map::MultiIndexMap;
 
 #[derive(MultiIndexMap)]

multi_index_map/tests/ordered_unique.rs

@@ -1,3 +1,5 @@
+#![cfg_attr(feature = "trivial_bounds", feature(trivial_bounds))]
+
 use multi_index_map::MultiIndexMap;
 
 #[derive(Hash, PartialEq, Eq, Clone, PartialOrd, Ord)]

multi_index_map_derive/Cargo.toml

@@ -31,3 +31,6 @@ convert_case = { version = "0.6" }
 
 [lib]
 proc-macro = true
+
+[features]
+trivial_bounds = []

multi_index_map_derive/src/generators.rs

@@ -36,27 +36,63 @@ pub(crate) fn generate_lookup_tables(
         let ty = &f.ty;
         let index_name = &idents.index_name;
 
-        match uniqueness {
-            Uniqueness::Unique => match ordering {
-                Ordering::Hashed => quote! {
-                    #index_name: ::multi_index_map::rustc_hash::FxHashMap<#ty, usize>,
-                },
-                Ordering::Ordered => quote! {
-                    #index_name: ::std::collections::BTreeMap<#ty, usize>,
-                },
-            },
-            Uniqueness::NonUnique => match ordering {
-                Ordering::Hashed => quote! {
-                    #index_name: ::multi_index_map::rustc_hash::FxHashMap<#ty, ::std::collections::BTreeSet<usize>>,
-                },
-                Ordering::Ordered => quote! {
-                    #index_name: ::std::collections::BTreeMap<#ty, ::std::collections::BTreeSet<usize>>,
-                },
-            },
+        let field_type = index_field_type(ty, ordering, uniqueness);
+
+        quote! {
+            #index_name: #field_type,
         }
     })
 }
 
+fn index_field_type(
+    ty: &Type,
+    ordering: &Ordering,
+    uniqueness: &Uniqueness,
+) -> ::proc_macro2::TokenStream {
+    match uniqueness {
+        Uniqueness::Unique => match ordering {
+            Ordering::Hashed => quote! {
+                ::multi_index_map::rustc_hash::FxHashMap<#ty, usize>
+            },
+            Ordering::Ordered => quote! {
+                ::std::collections::BTreeMap<#ty, usize>
+            },
+        },
+        Uniqueness::NonUnique => match ordering {
+            Ordering::Hashed => quote! {
+                ::multi_index_map::rustc_hash::FxHashMap<#ty, ::std::collections::BTreeSet<usize>>
+            },
+            Ordering::Ordered => quote! {
+                ::std::collections::BTreeMap<#ty, ::std::collections::BTreeSet<usize>>
+            },
+        },
+    }
+}
+
+// For each indexed field generate a TokenStream of the Debug bound for the field type and the multi_index_map specific type
+#[cfg(feature = "trivial_bounds")]
+pub(crate) fn generate_lookup_table_field_types(
+    fields: &[(Field, FieldIdents, Ordering, Uniqueness)],
+) -> impl Iterator<Item = ::proc_macro2::TokenStream> + '_ {
+    fields
+        .iter()
+        .flat_map(|(f, _idents, ordering, uniqueness)| {
+            let ty = &f.ty;
+
+            let type_debug = quote! {
+                #ty: ::core::fmt::Debug,
+            };
+
+            let field_type = index_field_type(ty, ordering, uniqueness);
+
+            let field_debug = quote! {
+                #field_type: ::core::fmt::Debug,
+            };
+
+            [type_debug, field_debug]
+        })
+}
+
 // For each indexed field generate a TokenStream representing initializing the lookup table.
 // Used in `with_capacity` initialization
 // If lookup table data structures support `with_capacity`, change `default()` and `new()` calls to
@@ -116,6 +152,20 @@ pub(crate) fn generate_lookup_table_shrink(
     })
 }
 
+// For each indexed field generate a TokenStream representing a debug struct field
+#[cfg(feature = "trivial_bounds")]
+pub(crate) fn generate_lookup_table_debug(
+    fields: &[(Field, FieldIdents, Ordering, Uniqueness)],
+) -> impl Iterator<Item = ::proc_macro2::TokenStream> + '_ {
+    fields.iter().map(|(_f, idents, _ordering, _uniqueness)| {
+        let index_name = &idents.index_name;
+
+        quote! {
+            .field(stringify!(#index_name), &self.#index_name)
+        }
+    })
+}
+
 // For each indexed field generate a TokenStream representing inserting the position
 //   in the backing storage to that field's lookup table
 // Unique indexed fields just require a simple insert to the map,
@@ -811,14 +861,39 @@ pub(crate) fn generate_expanded(
     lookup_table_fields_init: impl Iterator<Item = proc_macro2::TokenStream>,
     lookup_table_fields_shrink: impl Iterator<Item = proc_macro2::TokenStream>,
     lookup_table_fields_reserve: impl Iterator<Item = proc_macro2::TokenStream>,
+    #[cfg(feature = "trivial_bounds")] lookup_table_fields_debug: impl Iterator<
+        Item = proc_macro2::TokenStream,
+    >,
+    #[cfg(feature = "trivial_bounds")] lookup_table_field_types: impl Iterator<
+        Item = proc_macro2::TokenStream,
+    >,
 ) -> proc_macro2::TokenStream {
+    #[cfg(not(feature = "trivial_bounds"))]
+    let debug_impl = quote! {};
+
+    #[cfg(feature = "trivial_bounds")]
+    let debug_impl = quote! {
+        impl ::core::fmt::Debug for #map_name where #element_name: ::core::fmt::Debug,
+        #(#lookup_table_field_types)*
+         {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
+                f.debug_struct(stringify!(#map_name))
+                    .field("_store", &self._store)
+                    #(#lookup_table_fields_debug)*
+                    .finish()
+            }
+        }
+    };
+
     quote! {
         #[derive(Default)]
         #element_vis struct #map_name {
             _store: ::multi_index_map::slab::Slab<#element_name>,
             #(#lookup_table_fields)*
         }
 
+        #debug_impl
+
         impl #map_name {
             #element_vis fn with_capacity(n: usize) -> #map_name {
                 #map_name {

multi_index_map_derive/src/lib.rs

@@ -81,8 +81,14 @@ pub fn multi_index_map(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
 
     let lookup_table_fields_reserve = generators::generate_lookup_table_reserve(&indexed_fields);
 
+    #[cfg(feature = "trivial_bounds")]
+    let lookup_table_fields_debug = generators::generate_lookup_table_debug(&indexed_fields);
+
     let lookup_table_fields_shrink = generators::generate_lookup_table_shrink(&indexed_fields);
 
+    #[cfg(feature = "trivial_bounds")]
+    let lookup_table_field_types = generators::generate_lookup_table_field_types(&indexed_fields);
+
     let inserts = generators::generate_inserts(&indexed_fields);
 
     let removes = generators::generate_removes(&indexed_fields);
@@ -118,6 +124,10 @@ pub fn multi_index_map(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
         lookup_table_fields_init,
         lookup_table_fields_shrink,
         lookup_table_fields_reserve,
+        #[cfg(feature = "trivial_bounds")]
+        lookup_table_fields_debug,
+        #[cfg(feature = "trivial_bounds")]
+        lookup_table_field_types,
     );
 
     // Hand the output tokens back to the compiler.