Fix the lifetime error in ExplicitSelf

Had to take the infer context as a parameter instead of the type context, so that the function can be called during inference
rust-lang · bors · Nov 12, 2017 · Oct 20, 2017 · Nov 2, 2017 · Nov 5, 2017
commit a3f5866fe87a02254a3d4ab1debaa9e1ee460990
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
@@ -19,6 +19,7 @@ use hir::def::Def;
 use hir::def_id::DefId;
 use middle::resolve_lifetime as rl;
 use namespace::Namespace;
+use rustc::infer::InferCtxt;
 use rustc::ty::subst::{Kind, Subst, Substs};
 use rustc::traits;
 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
@@ -1433,26 +1434,21 @@ impl<'tcx> ExplicitSelf<'tcx> {
     /// ```
     ///
     pub fn determine<'a, 'gcx>(
-        tcx: TyCtxt<'a, 'gcx, 'tcx>,
+        infcx: &InferCtxt<'a, 'gcx, 'tcx>,
         param_env: ty::ParamEnv<'tcx>,
-        self_ty: Ty<'a>,
-        self_arg_ty: Ty<'a>
+        self_ty: Ty<'tcx>,
+        self_arg_ty: Ty<'tcx>
     ) -> ExplicitSelf<'tcx>
     {
         use self::ExplicitSelf::*;
 
-        tcx.infer_ctxt().enter(|infcx| {
-            let can_eq = |expected, actual| {
-                let cause = traits::ObligationCause::dummy();
-                infcx.at(&cause, param_env).eq(expected, actual).is_ok()
-            };
+        let can_eq = |expected, actual| infcx.can_eq(param_env, expected, actual).is_ok();
 
-            match self_arg_ty.sty {
-                _ if can_eq(self_arg_ty, self_ty) => ByValue,
-                ty::TyRef(region, ty::TypeAndMut { ty, mutbl}) if can_eq(ty, self_ty) => ByReference(region, mutbl),
-                ty::TyAdt(def, _) if def.is_box() && can_eq(self_arg_ty.boxed_ty(), self_ty) => ByBox,
-                _ => Other
-            }
-        })
+        match self_arg_ty.sty {
+            _ if can_eq(self_arg_ty, self_ty) => ByValue,
+            ty::TyRef(region, ty::TypeAndMut { ty, mutbl}) if can_eq(ty, self_ty) => ByReference(region, mutbl),
+            ty::TyAdt(def, _) if def.is_box() && can_eq(self_arg_ty.boxed_ty(), self_ty) => ByBox,
+            _ => Other
+        }
     }
 }
diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs
@@ -505,12 +505,14 @@ fn compare_self_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         let self_arg_ty = *tcx.fn_sig(method.def_id).input(0).skip_binder();
         let param_env = ty::ParamEnv::empty(Reveal::All);
 
-        match ExplicitSelf::determine(tcx, param_env, untransformed_self_ty, self_arg_ty) {
-            ExplicitSelf::ByValue => "self".to_string(),
-            ExplicitSelf::ByReference(_, hir::MutImmutable) => "&self".to_string(),
-            ExplicitSelf::ByReference(_, hir::MutMutable) => "&mut self".to_string(),
-            _ => format!("self: {}", self_arg_ty)
-        }
+        tcx.infer_ctxt().enter(|infcx| {
+            match ExplicitSelf::determine(&infcx, param_env, untransformed_self_ty, self_arg_ty) {
+                ExplicitSelf::ByValue => "self".to_string(),
+                ExplicitSelf::ByReference(_, hir::MutImmutable) => "&self".to_string(),
+                ExplicitSelf::ByReference(_, hir::MutMutable) => "&mut self".to_string(),
+                _ => format!("self: {}", self_arg_ty)
+            }
+        })
     };
 
     match (trait_m.method_has_self_argument, impl_m.method_has_self_argument) {

diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
@@ -471,25 +471,26 @@ impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
         let self_arg_ty = sig.inputs()[0];
 
         let cause = fcx.cause(span, ObligationCauseCode::MethodReceiver);
-        let at = fcx.at(&cause, fcx.param_env);
+        let eq = |expected, actual| fcx.at(&cause, fcx.param_env).eq(expected, actual);
         let mut autoderef = fcx.autoderef(span, self_arg_ty);
 
         loop {
             if let Some((potential_self_ty, _)) = autoderef.next() {
                 debug!("check_method_receiver: potential self type `{:?}` to match `{:?}`", potential_self_ty, self_ty);
 
-                if let Ok(InferOk { obligations, value: () }) = at.eq(self_ty, potential_self_ty) {
+                if let Ok(InferOk { obligations, value: () }) = eq(self_ty, potential_self_ty) {
                     fcx.register_predicates(obligations);
                     autoderef.finalize();
                     break;
                 }
 
             } else {
-                span_err!(fcx.tcx.sess, span, E0307, "invalid self type: {:?}", self_arg_ty);
+                span_err!(fcx.tcx.sess, span, E0307, "invalid `self` type: {:?}", self_arg_ty);
+                return;
             }
         }
 
-        if let ExplicitSelf::Other = ExplicitSelf::determine(fcx.tcx, fcx.param_env, self_ty, self_arg_ty) {
+        if let ExplicitSelf::Other = ExplicitSelf::determine(fcx, fcx.param_env, self_ty, self_arg_ty) {
             if !fcx.tcx.sess.features.borrow().arbitrary_self_types {
                 fcx.tcx.sess.span_err(span, "Arbitrary `self` types are experimental");
             }