| //! 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::collections::BTreeMap; |
| use std::mem; |
| |
| use rustc::ty; |
| use rustc_hir::def_id::DefId; |
| |
| use crate::clean; |
| use crate::clean::GenericArgs as PP; |
| use crate::clean::WherePredicate as WP; |
| use crate::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<_, Vec<_>> = 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_default().extend(bounds), |
| t => tybounds.push((t, bounds)), |
| }, |
| WP::RegionPredicate { lifetime, bounds } => { |
| lifetimes.push((lifetime, bounds)); |
| } |
| WP::EqPredicate { lhs, rhs } => equalities.push((lhs, rhs)), |
| } |
| } |
| |
| // Look for equality predicates on associated types that can be merged into |
| // general bound predicates |
| equalities.retain(|&(ref lhs, ref rhs)| { |
| let (self_, trait_did, name) = if let Some(p) = lhs.projection() { |
| p |
| } else { |
| return true; |
| }; |
| let generic = match self_ { |
| clean::Generic(s) => s, |
| _ => return true, |
| }; |
| let bounds = match params.get_mut(generic) { |
| Some(bound) => bound, |
| None => return true, |
| }; |
| |
| merge_bounds(cx, bounds, trait_did, name, rhs) |
| }); |
| |
| // And finally, let's reassemble everything |
| let mut clauses = Vec::new(); |
| clauses.extend( |
| lifetimes.into_iter().map(|(lt, bounds)| WP::RegionPredicate { lifetime: lt, 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, bounds })); |
| clauses.extend(equalities.into_iter().map(|(lhs, rhs)| WP::EqPredicate { lhs, rhs })); |
| clauses |
| } |
| |
| pub fn merge_bounds( |
| cx: &clean::DocContext<'_>, |
| bounds: &mut Vec<clean::GenericBound>, |
| trait_did: DefId, |
| name: &str, |
| rhs: &clean::Type, |
| ) -> bool { |
| !bounds.iter_mut().any(|b| { |
| let trait_ref = match *b { |
| clean::GenericBound::TraitBound(ref mut tr, _) => tr, |
| clean::GenericBound::Outlives(..) => 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().expect("segments were empty"); |
| match last.args { |
| PP::AngleBracketed { ref mut bindings, .. } => { |
| bindings.push(clean::TypeBinding { |
| name: name.to_string(), |
| kind: clean::TypeBindingKind::Equality { ty: rhs.clone() }, |
| }); |
| } |
| PP::Parenthesized { ref mut output, .. } => match output { |
| Some(o) => assert_eq!(o, rhs), |
| None => { |
| if *rhs != clean::Type::Tuple(Vec::new()) { |
| *output = Some(rhs.clone()); |
| } |
| } |
| }, |
| }; |
| true |
| }) |
| } |
| |
| pub fn ty_params(mut params: Vec<clean::GenericParamDef>) -> Vec<clean::GenericParamDef> { |
| for param in &mut params { |
| match param.kind { |
| clean::GenericParamDefKind::Type { ref mut bounds, .. } => { |
| *bounds = mem::take(bounds); |
| } |
| _ => panic!("expected only type parameters"), |
| } |
| } |
| params |
| } |
| |
| fn trait_is_same_or_supertrait(cx: &DocContext<'_>, child: DefId, trait_: DefId) -> bool { |
| if child == trait_ { |
| return true; |
| } |
| let predicates = cx.tcx.super_predicates_of(child); |
| debug_assert!(cx.tcx.generics_of(child).has_self); |
| let self_ty = cx.tcx.types.self_param; |
| predicates |
| .predicates |
| .iter() |
| .filter_map(|(pred, _)| { |
| if let ty::Predicate::Trait(ref pred) = *pred { |
| if pred.skip_binder().trait_ref.self_ty() == self_ty { |
| Some(pred.def_id()) |
| } else { |
| None |
| } |
| } else { |
| None |
| } |
| }) |
| .any(|did| trait_is_same_or_supertrait(cx, did, trait_)) |
| } |