1 //! This module contains functions to generate default trait impl function bodies where possible.
4 ast::{self, edit::AstNodeEdit, make, AstNode, NameOwner},
8 /// Generate custom trait bodies where possible.
10 /// Returns `Option` so that we can use `?` rather than `if let Some`. Returning
11 /// `None` means that generating a custom trait body failed, and the body will remain
12 /// as `todo!` instead.
13 pub(crate) fn gen_trait_fn_body(
15 trait_path: &ast::Path,
18 match trait_path.segment()?.name_ref()?.text().as_str() {
19 "Debug" => gen_debug_impl(adt, func),
20 "Default" => gen_default_impl(adt, func),
21 "Hash" => gen_hash_impl(adt, func),
26 /// Generate a `Debug` impl based on the fields and members of the target type.
27 fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
28 let annotated_name = adt.name()?;
30 // `Debug` cannot be derived for unions, so no default impl can be provided.
31 ast::Adt::Union(_) => None,
33 // => match self { Self::Variant => write!(f, "Variant") }
34 ast::Adt::Enum(enum_) => {
35 let list = enum_.variant_list()?;
36 let mut arms = vec![];
37 for variant in list.variants() {
38 let name = variant.name()?;
39 let left = make::ext::ident_path("Self");
40 let right = make::ext::ident_path(&format!("{}", name));
41 let variant_name = make::path_pat(make::path_concat(left, right));
43 let target = make::expr_path(make::ext::ident_path("f").into());
44 let fmt_string = make::expr_literal(&(format!("\"{}\"", name))).into();
45 let args = make::arg_list(vec![target, fmt_string]);
46 let macro_name = make::expr_path(make::ext::ident_path("write"));
47 let macro_call = make::expr_macro_call(macro_name, args);
49 arms.push(make::match_arm(Some(variant_name.into()), None, macro_call.into()));
52 let match_target = make::expr_path(make::ext::ident_path("self"));
53 let list = make::match_arm_list(arms).indent(ast::edit::IndentLevel(1));
54 let match_expr = make::expr_match(match_target, list);
56 let body = make::block_expr(None, Some(match_expr));
57 let body = body.indent(ast::edit::IndentLevel(1));
58 ted::replace(func.body()?.syntax(), body.clone_for_update().syntax());
62 ast::Adt::Struct(strukt) => {
63 let name = format!("\"{}\"", annotated_name);
64 let args = make::arg_list(Some(make::expr_literal(&name).into()));
65 let target = make::expr_path(make::ext::ident_path("f"));
67 let expr = match strukt.field_list() {
68 // => f.debug_struct("Name").finish()
69 None => make::expr_method_call(target, make::name_ref("debug_struct"), args),
71 // => f.debug_struct("Name").field("foo", &self.foo).finish()
72 Some(ast::FieldList::RecordFieldList(field_list)) => {
73 let method = make::name_ref("debug_struct");
74 let mut expr = make::expr_method_call(target, method, args);
75 for field in field_list.fields() {
76 let name = field.name()?;
77 let f_name = make::expr_literal(&(format!("\"{}\"", name))).into();
78 let f_path = make::expr_path(make::ext::ident_path("self"));
79 let f_path = make::expr_ref(f_path, false);
80 let f_path = make::expr_field(f_path, &format!("{}", name)).into();
81 let args = make::arg_list(vec![f_name, f_path]);
82 expr = make::expr_method_call(expr, make::name_ref("field"), args);
87 // => f.debug_tuple("Name").field(self.0).finish()
88 Some(ast::FieldList::TupleFieldList(field_list)) => {
89 let method = make::name_ref("debug_tuple");
90 let mut expr = make::expr_method_call(target, method, args);
91 for (idx, _) in field_list.fields().enumerate() {
92 let f_path = make::expr_path(make::ext::ident_path("self"));
93 let f_path = make::expr_ref(f_path, false);
94 let f_path = make::expr_field(f_path, &format!("{}", idx)).into();
95 let method = make::name_ref("field");
96 expr = make::expr_method_call(expr, method, make::arg_list(Some(f_path)));
102 let method = make::name_ref("finish");
103 let expr = make::expr_method_call(expr, method, make::arg_list(None));
104 let body = make::block_expr(None, Some(expr)).indent(ast::edit::IndentLevel(1));
105 ted::replace(func.body()?.syntax(), body.clone_for_update().syntax());
111 /// Generate a `Debug` impl based on the fields and members of the target type.
112 fn gen_default_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
113 fn gen_default_call() -> ast::Expr {
114 let trait_name = make::ext::ident_path("Default");
115 let method_name = make::ext::ident_path("default");
116 let fn_name = make::expr_path(make::path_concat(trait_name, method_name));
117 make::expr_call(fn_name, make::arg_list(None))
120 // `Debug` cannot be derived for unions, so no default impl can be provided.
121 ast::Adt::Union(_) => None,
122 // Deriving `Debug` for enums is not stable yet.
123 ast::Adt::Enum(_) => None,
124 ast::Adt::Struct(strukt) => {
125 let expr = match strukt.field_list() {
126 Some(ast::FieldList::RecordFieldList(field_list)) => {
127 let mut fields = vec![];
128 for field in field_list.fields() {
129 let method_call = gen_default_call();
130 let name_ref = make::name_ref(&field.name()?.to_string());
131 let field = make::record_expr_field(name_ref, Some(method_call));
134 let struct_name = make::ext::ident_path("Self");
135 let fields = make::record_expr_field_list(fields);
136 make::record_expr(struct_name, fields).into()
138 Some(ast::FieldList::TupleFieldList(field_list)) => {
139 let struct_name = make::expr_path(make::ext::ident_path("Self"));
140 let fields = field_list.fields().map(|_| gen_default_call());
141 make::expr_call(struct_name, make::arg_list(fields))
144 let struct_name = make::ext::ident_path("Self");
145 let fields = make::record_expr_field_list(None);
146 make::record_expr(struct_name, fields).into()
149 let body = make::block_expr(None, Some(expr)).indent(ast::edit::IndentLevel(1));
150 ted::replace(func.body()?.syntax(), body.clone_for_update().syntax());
156 /// Generate a `Hash` impl based on the fields and members of the target type.
157 fn gen_hash_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
158 fn gen_hash_call(target: ast::Expr) -> ast::Stmt {
159 let method = make::name_ref("hash");
160 let arg = make::expr_path(make::ext::ident_path("state"));
161 let expr = make::expr_method_call(target, method, make::arg_list(Some(arg)));
162 let stmt = make::expr_stmt(expr);
166 let body = match adt {
167 // `Hash` cannot be derived for unions, so no default impl can be provided.
168 ast::Adt::Union(_) => return None,
170 // => std::mem::discriminant(self).hash(state);
171 ast::Adt::Enum(_) => {
172 let root = make::ext::ident_path("core");
173 let submodule = make::ext::ident_path("mem");
174 let fn_name = make::ext::ident_path("discriminant");
175 let fn_name = make::path_concat(submodule, fn_name);
176 let fn_name = make::expr_path(make::path_concat(root, fn_name));
178 let arg = make::expr_path(make::ext::ident_path("self"));
179 let fn_call = make::expr_call(fn_name, make::arg_list(Some(arg)));
180 let stmt = gen_hash_call(fn_call);
182 make::block_expr(Some(stmt), None).indent(ast::edit::IndentLevel(1))
184 ast::Adt::Struct(strukt) => match strukt.field_list() {
185 // => self.<field>.hash(state);*
186 Some(ast::FieldList::RecordFieldList(field_list)) => {
187 let mut stmts = vec![];
188 for field in field_list.fields() {
189 let base = make::expr_path(make::ext::ident_path("self"));
190 let target = make::expr_field(base, &field.name()?.to_string());
191 stmts.push(gen_hash_call(target));
193 make::block_expr(stmts, None).indent(ast::edit::IndentLevel(1))
196 // => self.<field_index>.hash(state);*
197 Some(ast::FieldList::TupleFieldList(field_list)) => {
198 let mut stmts = vec![];
199 for (i, _) in field_list.fields().enumerate() {
200 let base = make::expr_path(make::ext::ident_path("self"));
201 let target = make::expr_field(base, &format!("{}", i));
202 stmts.push(gen_hash_call(target));
204 make::block_expr(stmts, None).indent(ast::edit::IndentLevel(1))
207 // No fields in the body means there's nothing to hash.
212 ted::replace(func.body()?.syntax(), body.clone_for_update().syntax());