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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Simplification of where clauses and parameter bounds into a prettier and
//! more canonical form.
//!
//! Currently all cross-crate-inlined function use `rustc::ty` to reconstruct
//! the AST (e.g. see all of `clean::inline`), but this is not always a
//! non-lossy transformation. The current format of storage for where clauses
//! for functions and such is simply a list of predicates. One example of this
//! is that the AST predicate of:
//!
//! where T: Trait<Foo=Bar>
//!
//! is encoded as:
//!
//! where T: Trait, <T as Trait>::Foo = Bar
//!
//! This module attempts to reconstruct the original where and/or parameter
//! bounds by special casing scenarios such as these. Fun!
use std::mem;
use std::collections::BTreeMap;
use rustc::hir::def_id::DefId;
use rustc::ty::subst;
use clean::PathParameters as PP;
use clean::WherePredicate as WP;
use clean::{self, Clean};
use core::DocContext;
pub fn where_clauses(cx: &DocContext, clauses: Vec<WP>) -> Vec<WP> {
// First, partition the where clause into its separate components
let mut params = BTreeMap::new();
let mut lifetimes = Vec::new();
let mut equalities = Vec::new();
let mut tybounds = Vec::new();
for clause in clauses {
match clause {
WP::BoundPredicate { ty, bounds } => {
match ty {
clean::Generic(s) => params.entry(s).or_insert(Vec::new())
.extend(bounds),
t => tybounds.push((t, ty_bounds(bounds))),
}
}
WP::RegionPredicate { lifetime, bounds } => {
lifetimes.push((lifetime, bounds));
}
WP::EqPredicate { lhs, rhs } => equalities.push((lhs, rhs)),
}
}
// Simplify the type parameter bounds on all the generics
let mut params = params.into_iter().map(|(k, v)| {
(k, ty_bounds(v))
}).collect::<BTreeMap<_, _>>();
// Look for equality predicates on associated types that can be merged into
// general bound predicates
equalities.retain(|&(ref lhs, ref rhs)| {
let (self_, trait_, name) = match *lhs {
clean::QPath { ref self_type, ref trait_, ref name } => {
(self_type, trait_, name)
}
_ => return true,
};
let generic = match **self_ {
clean::Generic(ref s) => s,
_ => return true,
};
let trait_did = match **trait_ {
clean::ResolvedPath { did, .. } => did,
_ => return true,
};
let bounds = match params.get_mut(generic) {
Some(bound) => bound,
None => return true,
};
!bounds.iter_mut().any(|b| {
let trait_ref = match *b {
clean::TraitBound(ref mut tr, _) => tr,
clean::RegionBound(..) => return false,
};
let (did, path) = match trait_ref.trait_ {
clean::ResolvedPath { did, ref mut path, ..} => (did, path),
_ => return false,
};
// If this QPath's trait `trait_did` is the same as, or a supertrait
// of, the bound's trait `did` then we can keep going, otherwise
// this is just a plain old equality bound.
if !trait_is_same_or_supertrait(cx, did, trait_did) {
return false
}
let last = path.segments.last_mut().unwrap();
match last.params {
PP::AngleBracketed { ref mut bindings, .. } => {
bindings.push(clean::TypeBinding {
name: name.clone(),
ty: rhs.clone(),
});
}
PP::Parenthesized { ref mut output, .. } => {
assert!(output.is_none());
*output = Some(rhs.clone());
}
};
true
})
});
// And finally, let's reassemble everything
let mut clauses = Vec::new();
clauses.extend(lifetimes.into_iter().map(|(lt, bounds)| {
WP::RegionPredicate { lifetime: lt, bounds: bounds }
}));
clauses.extend(params.into_iter().map(|(k, v)| {
WP::BoundPredicate {
ty: clean::Generic(k),
bounds: v,
}
}));
clauses.extend(tybounds.into_iter().map(|(ty, bounds)| {
WP::BoundPredicate { ty: ty, bounds: bounds }
}));
clauses.extend(equalities.into_iter().map(|(lhs, rhs)| {
WP::EqPredicate { lhs: lhs, rhs: rhs }
}));
clauses
}
pub fn ty_params(mut params: Vec<clean::TyParam>) -> Vec<clean::TyParam> {
for param in &mut params {
param.bounds = ty_bounds(mem::replace(&mut param.bounds, Vec::new()));
}
return params;
}
fn ty_bounds(bounds: Vec<clean::TyParamBound>) -> Vec<clean::TyParamBound> {
bounds
}
fn trait_is_same_or_supertrait(cx: &DocContext, child: DefId,
trait_: DefId) -> bool {
if child == trait_ {
return true
}
let def = cx.tcx().lookup_trait_def(child);
let predicates = cx.tcx().lookup_predicates(child);
let generics = (&def.generics, &predicates, subst::TypeSpace).clean(cx);
generics.where_predicates.iter().filter_map(|pred| {
match *pred {
clean::WherePredicate::BoundPredicate {
ty: clean::Generic(ref s),
ref bounds
} if *s == "Self" => Some(bounds),
_ => None,
}
}).flat_map(|bounds| bounds).any(|bound| {
let poly_trait = match *bound {
clean::TraitBound(ref t, _) => t,
_ => return false,
};
match poly_trait.trait_ {
clean::ResolvedPath { did, .. } => {
trait_is_same_or_supertrait(cx, did, trait_)
}
_ => false,
}
})
}