Auto merge of #44896 - qmx:move-resolve-to-librustc, r=arielb1

Move monomorphize::resolve() to librustc

this moves `monomorphize::resolve(..)` to librustc, and re-enables inlining for some trait methods, fixing #44389

@nikomatsakis I've kept the calls to the new `ty::Instance::resolve(....)` always `.unwrap()`-ing for the moment, how/do you want to add more debugging info via `.unwrap_or()` or something like this?

we still have some related `resolve_*` functions on monomorphize, but I wasn't sure moving them was into the scope for this PR too.

@eddyb mind to take a look too?

src/librustc/ty/instance.rs

@@ -10,6 +10,10 @@
 
 use hir::def_id::DefId;
 use ty::{self, Ty, TypeFoldable, Substs, TyCtxt};
+use ty::subst::{Kind, Subst};
+use traits;
+use syntax::abi::Abi;
+use syntax::codemap::DUMMY_SP;
 use util::ppaux;
 
 use std::fmt;
@@ -111,4 +115,211 @@ impl<'a, 'b, 'tcx> Instance<'tcx> {
     pub fn def_id(&self) -> DefId {
         self.def.def_id()
     }
+
+    /// Resolve a (def_id, substs) pair to an (optional) instance -- most commonly,
+    /// this is used to find the precise code that will run for a trait method invocation,
+    /// if known.
+    ///
+    /// Returns `None` if we cannot resolve `Instance` to a specific instance.
+    /// For example, in a context like this,
+    ///
+    /// ```
+    /// fn foo<T: Debug>(t: T) { ... }
+    /// ```
+    ///
+    /// trying to resolve `Debug::fmt` applied to `T` will yield `None`, because we do not
+    /// know what code ought to run. (Note that this setting is also affected by the
+    /// `RevealMode` in the parameter environment.)
+    ///
+    /// Presuming that coherence and type-check have succeeded, if this method is invoked
+    /// in a monomorphic context (i.e., like during trans), then it is guaranteed to return
+    /// `Some`.
+    pub fn resolve(tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                   param_env: ty::ParamEnv<'tcx>,
+                   def_id: DefId,
+                   substs: &'tcx Substs<'tcx>) -> Option<Instance<'tcx>> {
+        debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
+        let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
+            debug!(" => associated item, attempting to find impl");
+            let item = tcx.associated_item(def_id);
+            resolve_associated_item(tcx, &item, param_env, trait_def_id, substs)
+        } else {
+            let ty = tcx.type_of(def_id);
+            let item_type = tcx.trans_apply_param_substs(substs, &ty);
+
+            let def = match item_type.sty {
+                ty::TyFnDef(..) if {
+                    let f = item_type.fn_sig(tcx);
+                    f.abi() == Abi::RustIntrinsic ||
+                        f.abi() == Abi::PlatformIntrinsic
+                } =>
+                {
+                    debug!(" => intrinsic");
+                    ty::InstanceDef::Intrinsic(def_id)
+                }
+                _ => {
+                    if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
+                        let ty = substs.type_at(0);
+                        if ty.needs_drop(tcx, ty::ParamEnv::empty(traits::Reveal::All)) {
+                            debug!(" => nontrivial drop glue");
+                            ty::InstanceDef::DropGlue(def_id, Some(ty))
+                        } else {
+                            debug!(" => trivial drop glue");
+                            ty::InstanceDef::DropGlue(def_id, None)
+                        }
+                    } else {
+                        debug!(" => free item");
+                        ty::InstanceDef::Item(def_id)
+                    }
+                }
+            };
+            Some(Instance {
+                def: def,
+                substs: substs
+            })
+        };
+        debug!("resolve(def_id={:?}, substs={:?}) = {:?}", def_id, substs, result);
+        result
+    }
+}
+
+fn resolve_closure<'a, 'tcx>(
+                   tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                   def_id: DefId,
+                   substs: ty::ClosureSubsts<'tcx>,
+                   requested_kind: ty::ClosureKind)
+-> Instance<'tcx>
+{
+    let actual_kind = tcx.closure_kind(def_id);
+
+    match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
+        Ok(true) => fn_once_adapter_instance(tcx, def_id, substs),
+        _ => Instance::new(def_id, substs.substs)
+    }
+}
+
+fn resolve_associated_item<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    trait_item: &ty::AssociatedItem,
+    param_env: ty::ParamEnv<'tcx>,
+    trait_id: DefId,
+    rcvr_substs: &'tcx Substs<'tcx>
+    ) -> Option<Instance<'tcx>> {
+    let def_id = trait_item.def_id;
+    debug!("resolve_associated_item(trait_item={:?}, \
+                                    trait_id={:?}, \
+           rcvr_substs={:?})",
+           def_id, trait_id, rcvr_substs);
+
+    let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
+    let vtbl = tcx.trans_fulfill_obligation(DUMMY_SP, param_env, ty::Binder(trait_ref));
+
+    // Now that we know which impl is being used, we can dispatch to
+    // the actual function:
+    match vtbl {
+        traits::VtableImpl(impl_data) => {
+            let (def_id, substs) = traits::find_associated_item(
+                tcx, trait_item, rcvr_substs, &impl_data);
+            let substs = tcx.erase_regions(&substs);
+            Some(ty::Instance::new(def_id, substs))
+        }
+        traits::VtableGenerator(closure_data) => {
+            Some(Instance {
+                def: ty::InstanceDef::Item(closure_data.closure_def_id),
+                substs: closure_data.substs.substs
+            })
+        }
+        traits::VtableClosure(closure_data) => {
+            let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
+            Some(resolve_closure(tcx, closure_data.closure_def_id, closure_data.substs,
+                                 trait_closure_kind))
+        }
+        traits::VtableFnPointer(ref data) => {
+            Some(Instance {
+                def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
+                substs: rcvr_substs
+            })
+        }
+        traits::VtableObject(ref data) => {
+            let index = tcx.get_vtable_index_of_object_method(data, def_id);
+            Some(Instance {
+                def: ty::InstanceDef::Virtual(def_id, index),
+                substs: rcvr_substs
+            })
+        }
+        traits::VtableBuiltin(..) => {
+            if let Some(_) = tcx.lang_items().clone_trait() {
+                Some(Instance {
+                    def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
+                    substs: rcvr_substs
+                })
+            } else {
+                None
+            }
+        }
+        traits::VtableDefaultImpl(..) | traits::VtableParam(..) => None
+    }
+}
+
+fn needs_fn_once_adapter_shim<'a, 'tcx>(actual_closure_kind: ty::ClosureKind,
+                              trait_closure_kind: ty::ClosureKind)
+    -> Result<bool, ()>
+{
+    match (actual_closure_kind, trait_closure_kind) {
+        (ty::ClosureKind::Fn, ty::ClosureKind::Fn) |
+            (ty::ClosureKind::FnMut, ty::ClosureKind::FnMut) |
+            (ty::ClosureKind::FnOnce, ty::ClosureKind::FnOnce) => {
+                // No adapter needed.
+                Ok(false)
+            }
+        (ty::ClosureKind::Fn, ty::ClosureKind::FnMut) => {
+            // The closure fn `llfn` is a `fn(&self, ...)`.  We want a
+            // `fn(&mut self, ...)`. In fact, at trans time, these are
+            // basically the same thing, so we can just return llfn.
+            Ok(false)
+        }
+        (ty::ClosureKind::Fn, ty::ClosureKind::FnOnce) |
+            (ty::ClosureKind::FnMut, ty::ClosureKind::FnOnce) => {
+                // The closure fn `llfn` is a `fn(&self, ...)` or `fn(&mut
+                // self, ...)`.  We want a `fn(self, ...)`. We can produce
+                // this by doing something like:
+                //
+                //     fn call_once(self, ...) { call_mut(&self, ...) }
+                //     fn call_once(mut self, ...) { call_mut(&mut self, ...) }
+                //
+                // These are both the same at trans time.
+                Ok(true)
+        }
+        (ty::ClosureKind::FnMut, _) |
+        (ty::ClosureKind::FnOnce, _) => Err(())
+    }
+}
+
+fn fn_once_adapter_instance<'a, 'tcx>(
+                            tcx: TyCtxt<'a, 'tcx, 'tcx>,
+                            closure_did: DefId,
+                            substs: ty::ClosureSubsts<'tcx>,
+                            ) -> Instance<'tcx> {
+    debug!("fn_once_adapter_shim({:?}, {:?})",
+    closure_did,
+    substs);
+    let fn_once = tcx.lang_items().fn_once_trait().unwrap();
+    let call_once = tcx.associated_items(fn_once)
+        .find(|it| it.kind == ty::AssociatedKind::Method)
+        .unwrap().def_id;
+    let def = ty::InstanceDef::ClosureOnceShim { call_once };
+
+    let self_ty = tcx.mk_closure_from_closure_substs(
+        closure_did, substs);
+
+    let sig = tcx.fn_sig(closure_did).subst(tcx, substs.substs);
+    let sig = tcx.erase_late_bound_regions_and_normalize(&sig);
+    assert_eq!(sig.inputs().len(), 1);
+    let substs = tcx.mk_substs([
+                               Kind::from(self_ty),
+                               Kind::from(sig.inputs()[0]),
+    ].iter().cloned());
+
+    debug!("fn_once_adapter_shim: self_ty={:?} sig={:?}", self_ty, sig);
+    Instance { def, substs }
 }

src/librustc_mir/transform/inline.rs

@@ -18,7 +18,7 @@ use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 use rustc::mir::*;
 use rustc::mir::transform::{MirPass, MirSource};
 use rustc::mir::visit::*;
-use rustc::ty::{self, Ty, TyCtxt};
+use rustc::ty::{self, Ty, TyCtxt, Instance};
 use rustc::ty::subst::{Subst,Substs};
 
 use std::collections::VecDeque;
@@ -78,7 +78,7 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
         let mut callsites = VecDeque::new();
 
         // Only do inlining into fn bodies.
-        if let MirSource::Fn(_) = self.source {
+        if let MirSource::Fn(caller_id) = self.source {
             for (bb, bb_data) in caller_mir.basic_blocks().iter_enumerated() {
                 // Don't inline calls that are in cleanup blocks.
                 if bb_data.is_cleanup { continue; }
@@ -87,17 +87,23 @@ impl<'a, 'tcx> Inliner<'a, 'tcx> {
                 let terminator = bb_data.terminator();
                 if let TerminatorKind::Call {
                     func: Operand::Constant(ref f), .. } = terminator.kind {
-                    if let ty::TyFnDef(callee_def_id, substs) = f.ty.sty {
-                        if self.tcx.trait_of_item(callee_def_id).is_none() {
-                            callsites.push_back(CallSite {
-                                callee: callee_def_id,
-                                substs,
-                                bb,
-                                location: terminator.source_info
-                            });
+                        if let ty::TyFnDef(callee_def_id, substs) = f.ty.sty {
+                            let caller_def_id = self.tcx.hir.local_def_id(caller_id);
+                            let param_env = self.tcx.param_env(caller_def_id);
+
+                            if let Some(instance) = Instance::resolve(self.tcx,
+                                                                      param_env,
+                                                                      callee_def_id,
+                                                                      substs) {
+                                callsites.push_back(CallSite {
+                                    callee: instance.def_id(),
+                                    substs: instance.substs,
+                                    bb,
+                                    location: terminator.source_info
+                                });
+                            }
                         }
                     }
-                }
             }
         }
 

src/librustc_trans/callee.rs

@@ -19,9 +19,10 @@ use common::{self, CrateContext};
 use consts;
 use declare;
 use llvm::{self, ValueRef};
-use monomorphize::{self, Instance};
+use monomorphize::Instance;
 use rustc::hir::def_id::DefId;
-use rustc::ty::TypeFoldable;
+use rustc::ty::{self, TypeFoldable};
+use rustc::traits;
 use rustc::ty::subst::Substs;
 use type_of;
 
@@ -179,5 +180,13 @@ pub fn resolve_and_get_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
                                     substs: &'tcx Substs<'tcx>)
                                     -> ValueRef
 {
-    get_fn(ccx, monomorphize::resolve(ccx.tcx(), def_id, substs))
+    get_fn(
+        ccx,
+        ty::Instance::resolve(
+            ccx.tcx(),
+            ty::ParamEnv::empty(traits::Reveal::All),
+            def_id,
+            substs
+        ).unwrap()
+    )
 }

src/librustc_trans/collector.rs

@@ -566,7 +566,10 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
         if let ConstVal::Unevaluated(def_id, substs) = constant.val {
             let substs = self.tcx.trans_apply_param_substs(self.param_substs,
                                                            &substs);
-            let instance = monomorphize::resolve(self.tcx, def_id, substs);
+            let instance = ty::Instance::resolve(self.tcx,
+                                                 ty::ParamEnv::empty(traits::Reveal::All),
+                                                 def_id,
+                                                 substs).unwrap();
             collect_neighbours(self.tcx, instance, true, self.output);
         }
 
@@ -587,7 +590,11 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
 
                 let constness = match (self.const_context, &callee_ty.sty) {
                     (true, &ty::TyFnDef(def_id, substs)) if self.tcx.is_const_fn(def_id) => {
-                        let instance = monomorphize::resolve(self.tcx, def_id, substs);
+                        let instance =
+                            ty::Instance::resolve(self.tcx,
+                                                  ty::ParamEnv::empty(traits::Reveal::All),
+                                                  def_id,
+                                                  substs).unwrap();
                         Some(instance)
                     }
                     _ => None
@@ -657,7 +664,10 @@ fn visit_fn_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           output: &mut Vec<TransItem<'tcx>>)
 {
     if let ty::TyFnDef(def_id, substs) = ty.sty {
-        let instance = monomorphize::resolve(tcx, def_id, substs);
+        let instance = ty::Instance::resolve(tcx,
+                                             ty::ParamEnv::empty(traits::Reveal::All),
+                                             def_id,
+                                             substs).unwrap();
         visit_instance_use(tcx, instance, is_direct_call, output);
     }
 }
@@ -845,7 +855,11 @@ fn create_trans_items_for_vtable_methods<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             // Walk all methods of the trait, including those of its supertraits
             let methods = traits::get_vtable_methods(tcx, poly_trait_ref);
             let methods = methods.filter_map(|method| method)
-                .map(|(def_id, substs)| monomorphize::resolve(tcx, def_id, substs))
+                .map(|(def_id, substs)| ty::Instance::resolve(
+                        tcx,
+                        ty::ParamEnv::empty(traits::Reveal::All),
+                        def_id,
+                        substs).unwrap())
                 .filter(|&instance| should_trans_locally(tcx, &instance))
                 .map(|instance| create_fn_trans_item(instance));
             output.extend(methods);
@@ -1000,8 +1014,10 @@ fn create_trans_items_for_default_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                         continue;
                     }
 
-                    let instance =
-                        monomorphize::resolve(tcx, method.def_id, callee_substs);
+                    let instance = ty::Instance::resolve(tcx,
+                                                         ty::ParamEnv::empty(traits::Reveal::All),
+                                                         method.def_id,
+                                                         callee_substs).unwrap();
 
                     let trans_item = create_fn_trans_item(instance);
                     if trans_item.is_instantiable(tcx) && should_trans_locally(tcx, &instance) {

src/librustc_trans/mir/block.rs

@@ -13,6 +13,7 @@ use rustc::middle::lang_items;
 use rustc::middle::const_val::{ConstEvalErr, ConstInt, ErrKind};
 use rustc::ty::{self, Ty, TypeFoldable};
 use rustc::ty::layout::{self, LayoutTyper};
+use rustc::traits;
 use rustc::mir;
 use abi::{Abi, FnType, ArgType};
 use adt;
@@ -429,7 +430,10 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
 
                 let (instance, mut llfn) = match callee.ty.sty {
                     ty::TyFnDef(def_id, substs) => {
-                        (Some(monomorphize::resolve(bcx.ccx.tcx(), def_id, substs)),
+                        (Some(ty::Instance::resolve(bcx.ccx.tcx(),
+                                                    ty::ParamEnv::empty(traits::Reveal::All),
+                                                    def_id,
+                                                    substs).unwrap()),
                          None)
                     }
                     ty::TyFnPtr(_) => {

src/librustc_trans/mir/constant.rs

@@ -14,6 +14,7 @@ use rustc_const_math::ConstInt::*;
 use rustc_const_math::{ConstInt, ConstMathErr};
 use rustc::hir::def_id::DefId;
 use rustc::infer::TransNormalize;
+use rustc::traits;
 use rustc::mir;
 use rustc::mir::tcx::LvalueTy;
 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
@@ -30,7 +31,6 @@ use common::{C_array, C_bool, C_bytes, C_int, C_uint, C_big_integral, C_u32, C_u
 use common::{C_null, C_struct, C_str_slice, C_undef, C_usize, C_vector, is_undef};
 use common::const_to_opt_u128;
 use consts;
-use monomorphize;
 use type_of;
 use type_::Type;
 use value::Value;
@@ -261,7 +261,10 @@ impl<'a, 'tcx> MirConstContext<'a, 'tcx> {
                  substs: &'tcx Substs<'tcx>,
                  args: IndexVec<mir::Local, Result<Const<'tcx>, ConstEvalErr<'tcx>>>)
                  -> Result<Const<'tcx>, ConstEvalErr<'tcx>> {
-        let instance = monomorphize::resolve(ccx.tcx(), def_id, substs);
+        let instance = ty::Instance::resolve(ccx.tcx(),
+                                             ty::ParamEnv::empty(traits::Reveal::All),
+                                             def_id,
+                                             substs).unwrap();
         let mir = ccx.tcx().instance_mir(instance.def);
         MirConstContext::new(ccx, &mir, instance.substs, args).trans()
     }

src/librustc_trans/monomorphize.rs

@@ -8,9 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use abi::Abi;
-use common::*;
-
 use rustc::hir::def_id::DefId;
 use rustc::middle::lang_items::DropInPlaceFnLangItem;
 use rustc::traits;
@@ -99,115 +96,6 @@ pub fn resolve_closure<'a, 'tcx> (
     }
 }
 
-fn resolve_associated_item<'a, 'tcx>(
-    tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    trait_item: &ty::AssociatedItem,
-    trait_id: DefId,
-    rcvr_substs: &'tcx Substs<'tcx>
-) -> Instance<'tcx> {
-    let def_id = trait_item.def_id;
-    debug!("resolve_associated_item(trait_item={:?}, \
-                                    trait_id={:?}, \
-                                    rcvr_substs={:?})",
-           def_id, trait_id, rcvr_substs);
-
-    let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
-    let vtbl = tcx.trans_fulfill_obligation(
-        DUMMY_SP, ty::ParamEnv::empty(traits::Reveal::All), ty::Binder(trait_ref));
-
-    // Now that we know which impl is being used, we can dispatch to
-    // the actual function:
-    match vtbl {
-        traits::VtableImpl(impl_data) => {
-            let (def_id, substs) = traits::find_associated_item(
-                tcx, trait_item, rcvr_substs, &impl_data);
-            let substs = tcx.erase_regions(&substs);
-            ty::Instance::new(def_id, substs)
-        }
-        traits::VtableGenerator(closure_data) => {
-            Instance {
-                def: ty::InstanceDef::Item(closure_data.closure_def_id),
-                substs: closure_data.substs.substs
-            }
-        }
-        traits::VtableClosure(closure_data) => {
-            let trait_closure_kind = tcx.lang_items().fn_trait_kind(trait_id).unwrap();
-            resolve_closure(tcx, closure_data.closure_def_id, closure_data.substs,
-                            trait_closure_kind)
-        }
-        traits::VtableFnPointer(ref data) => {
-            Instance {
-                def: ty::InstanceDef::FnPtrShim(trait_item.def_id, data.fn_ty),
-                substs: rcvr_substs
-            }
-        }
-        traits::VtableObject(ref data) => {
-            let index = tcx.get_vtable_index_of_object_method(data, def_id);
-            Instance {
-                def: ty::InstanceDef::Virtual(def_id, index),
-                substs: rcvr_substs
-            }
-        }
-        traits::VtableBuiltin(..) if Some(trait_id) == tcx.lang_items().clone_trait() => {
-            Instance {
-                def: ty::InstanceDef::CloneShim(def_id, trait_ref.self_ty()),
-                substs: rcvr_substs
-            }
-        }
-        _ => {
-            bug!("static call to invalid vtable: {:?}", vtbl)
-        }
-    }
-}
-
-/// The point where linking happens. Resolve a (def_id, substs)
-/// pair to an instance.
-pub fn resolve<'a, 'tcx>(
-    tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    def_id: DefId,
-    substs: &'tcx Substs<'tcx>
-) -> Instance<'tcx> {
-    debug!("resolve(def_id={:?}, substs={:?})",
-           def_id, substs);
-    let result = if let Some(trait_def_id) = tcx.trait_of_item(def_id) {
-        debug!(" => associated item, attempting to find impl");
-        let item = tcx.associated_item(def_id);
-        resolve_associated_item(tcx, &item, trait_def_id, substs)
-    } else {
-        let item_type = def_ty(tcx, def_id, substs);
-        let def = match item_type.sty {
-            ty::TyFnDef(..) if {
-                    let f = item_type.fn_sig(tcx);
-                    f.abi() == Abi::RustIntrinsic ||
-                    f.abi() == Abi::PlatformIntrinsic
-                } =>
-            {
-                debug!(" => intrinsic");
-                ty::InstanceDef::Intrinsic(def_id)
-            }
-            _ => {
-                if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
-                    let ty = substs.type_at(0);
-                    if type_needs_drop(tcx, ty) {
-                        debug!(" => nontrivial drop glue");
-                        ty::InstanceDef::DropGlue(def_id, Some(ty))
-                    } else {
-                        debug!(" => trivial drop glue");
-                        ty::InstanceDef::DropGlue(def_id, None)
-                    }
-                } else {
-                    debug!(" => free item");
-                    ty::InstanceDef::Item(def_id)
-                }
-            }
-        };
-        Instance { def, substs }
-    };
-    debug!("resolve(def_id={:?}, substs={:?}) = {}",
-           def_id, substs, result);
-    result
-}
-
 pub fn resolve_drop_in_place<'a, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     ty: Ty<'tcx>)
@@ -215,7 +103,7 @@ pub fn resolve_drop_in_place<'a, 'tcx>(
 {
     let def_id = tcx.require_lang_item(DropInPlaceFnLangItem);
     let substs = tcx.intern_substs(&[Kind::from(ty)]);
-    resolve(tcx, def_id, substs)
+    Instance::resolve(tcx, ty::ParamEnv::empty(traits::Reveal::All), def_id, substs).unwrap()
 }
 
 pub fn custom_coerce_unsize_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,