1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Simplification of where clauses and parameter bounds into a prettier and
12 //! more canonical form.
14 //! Currently all cross-crate-inlined function use `rustc::ty` to reconstruct
15 //! the AST (e.g., see all of `clean::inline`), but this is not always a
16 //! non-lossy transformation. The current format of storage for where clauses
17 //! for functions and such is simply a list of predicates. One example of this
18 //! is that the AST predicate of: `where T: Trait<Foo=Bar>` is encoded as:
19 //! `where T: Trait, <T as Trait>::Foo = Bar`.
21 //! This module attempts to reconstruct the original where and/or parameter
22 //! bounds by special casing scenarios such as these. Fun!
25 use std::collections::BTreeMap;
27 use rustc::hir::def_id::DefId;
30 use clean::GenericArgs as PP;
31 use clean::WherePredicate as WP;
35 pub fn where_clauses(cx: &DocContext, clauses: Vec<WP>) -> Vec<WP> {
36 // First, partition the where clause into its separate components
37 let mut params: BTreeMap<_, Vec<_>> = BTreeMap::new();
38 let mut lifetimes = Vec::new();
39 let mut equalities = Vec::new();
40 let mut tybounds = Vec::new();
42 for clause in clauses {
44 WP::BoundPredicate { ty, bounds } => {
46 clean::Generic(s) => params.entry(s).or_default()
48 t => tybounds.push((t, ty_bounds(bounds))),
51 WP::RegionPredicate { lifetime, bounds } => {
52 lifetimes.push((lifetime, bounds));
54 WP::EqPredicate { lhs, rhs } => equalities.push((lhs, rhs)),
58 // Simplify the type parameter bounds on all the generics
59 let mut params = params.into_iter().map(|(k, v)| {
61 }).collect::<BTreeMap<_, _>>();
63 // Look for equality predicates on associated types that can be merged into
64 // general bound predicates
65 equalities.retain(|&(ref lhs, ref rhs)| {
66 let (self_, trait_, name) = match *lhs {
67 clean::QPath { ref self_type, ref trait_, ref name } => {
68 (self_type, trait_, name)
72 let generic = match **self_ {
73 clean::Generic(ref s) => s,
76 let trait_did = match **trait_ {
77 clean::ResolvedPath { did, .. } => did,
80 let bounds = match params.get_mut(generic) {
84 !bounds.iter_mut().any(|b| {
85 let trait_ref = match *b {
86 clean::GenericBound::TraitBound(ref mut tr, _) => tr,
87 clean::GenericBound::Outlives(..) => return false,
89 let (did, path) = match trait_ref.trait_ {
90 clean::ResolvedPath { did, ref mut path, ..} => (did, path),
93 // If this QPath's trait `trait_did` is the same as, or a supertrait
94 // of, the bound's trait `did` then we can keep going, otherwise
95 // this is just a plain old equality bound.
96 if !trait_is_same_or_supertrait(cx, did, trait_did) {
99 let last = path.segments.last_mut().expect("segments were empty");
101 PP::AngleBracketed { ref mut bindings, .. } => {
102 bindings.push(clean::TypeBinding {
107 PP::Parenthesized { ref mut output, .. } => {
108 assert!(output.is_none());
109 if *rhs != clean::Type::Tuple(Vec::new()) {
110 *output = Some(rhs.clone());
118 // And finally, let's reassemble everything
119 let mut clauses = Vec::new();
120 clauses.extend(lifetimes.into_iter().map(|(lt, bounds)| {
121 WP::RegionPredicate { lifetime: lt, bounds: bounds }
123 clauses.extend(params.into_iter().map(|(k, v)| {
125 ty: clean::Generic(k),
129 clauses.extend(tybounds.into_iter().map(|(ty, bounds)| {
130 WP::BoundPredicate { ty: ty, bounds: bounds }
132 clauses.extend(equalities.into_iter().map(|(lhs, rhs)| {
133 WP::EqPredicate { lhs: lhs, rhs: rhs }
138 pub fn ty_params(mut params: Vec<clean::GenericParamDef>) -> Vec<clean::GenericParamDef> {
139 for param in &mut params {
141 clean::GenericParamDefKind::Type { ref mut bounds, .. } => {
142 *bounds = ty_bounds(mem::replace(bounds, Vec::new()));
144 _ => panic!("expected only type parameters"),
150 fn ty_bounds(bounds: Vec<clean::GenericBound>) -> Vec<clean::GenericBound> {
154 fn trait_is_same_or_supertrait(cx: &DocContext, child: DefId,
155 trait_: DefId) -> bool {
159 let predicates = cx.tcx.super_predicates_of(child);
160 predicates.predicates.iter().filter_map(|(pred, _)| {
161 if let ty::Predicate::Trait(ref pred) = *pred {
162 if pred.skip_binder().trait_ref.self_ty().is_self() {
170 }).any(|did| trait_is_same_or_supertrait(cx, did, trait_))