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Support coercion between (FnDef | Closure) and (FnDef | Closure) when Closure is non-capturing

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This commit is contained in:
Donough Liu 2020-05-07 13:11:24 +08:00
parent 7ebd87a7a1
commit 59cc5b1ba3
3 changed files with 81 additions and 33 deletions
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21
src/librustc_middle/ty/context.rs
View File

@ -2056,24 +2056,25 @@ impl<'tcx> TyCtxt<'tcx> {
self.mk_fn_ptr(sig.map_bound(|sig| ty::FnSig { unsafety: hir::Unsafety::Unsafe, ..sig }))
}
/// Given a closure signature `sig`, returns an equivalent `fn`
/// type with the same signature. Detuples and so forth -- so
/// e.g., if we have a sig with `Fn<(u32, i32)>` then you would get
/// a `fn(u32, i32)`.
/// `unsafety` determines the unsafety of the `fn` type. If you pass
/// Given a closure signature, returns an equivalent fn signature. Detuples
/// and so forth -- so e.g., if we have a sig with `Fn<(u32, i32)>` then
/// you would get a `fn(u32, i32)`.
/// `unsafety` determines the unsafety of the fn signature. If you pass
/// `hir::Unsafety::Unsafe` in the previous example, then you would get
/// an `unsafe fn (u32, i32)`.
/// It cannot convert a closure that requires unsafe.
pub fn coerce_closure_fn_ty(self, sig: PolyFnSig<'tcx>, unsafety: hir::Unsafety) -> Ty<'tcx> {
let converted_sig = sig.map_bound(|s| {
pub fn signature_unclosure(
self,
sig: PolyFnSig<'tcx>,
unsafety: hir::Unsafety,
) -> PolyFnSig<'tcx> {
sig.map_bound(|s| {
let params_iter = match s.inputs()[0].kind {
ty::Tuple(params) => params.into_iter().map(|k| k.expect_ty()),
_ => bug!(),
};
self.mk_fn_sig(params_iter, s.output(), s.c_variadic, unsafety, abi::Abi::Rust)
});
self.mk_fn_ptr(converted_sig)
})
}
#[allow(rustc::usage_of_ty_tykind)]

2
src/librustc_mir/borrow_check/type_check/mod.rs
View File

@ -2087,7 +2087,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
ty::Closure(_, substs) => substs.as_closure().sig(),
_ => bug!(),
};
let ty_fn_ptr_from = tcx.coerce_closure_fn_ty(sig, *unsafety);
let ty_fn_ptr_from = tcx.mk_fn_ptr(tcx.signature_unclosure(sig, *unsafety));
if let Err(terr) = self.eq_types(
ty_fn_ptr_from,

91
src/librustc_typeck/check/coercion.rs
View File

@ -759,7 +759,8 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
// `unsafe fn(arg0,arg1,...) -> _`
let closure_sig = substs_a.as_closure().sig();
let unsafety = fn_ty.unsafety();
let pointer_ty = self.tcx.coerce_closure_fn_ty(closure_sig, unsafety);
let pointer_ty =
self.tcx.mk_fn_ptr(self.tcx.signature_unclosure(closure_sig, unsafety));
debug!("coerce_closure_to_fn(a={:?}, b={:?}, pty={:?})", a, b, pointer_ty);
self.unify_and(
pointer_ty,
@ -875,23 +876,63 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
debug!("coercion::try_find_coercion_lub({:?}, {:?})", prev_ty, new_ty);
// Special-case that coercion alone cannot handle:
// Two function item types of differing IDs or InternalSubsts.
if let (&ty::FnDef(..), &ty::FnDef(..)) = (&prev_ty.kind, &new_ty.kind) {
// Don't reify if the function types have a LUB, i.e., they
// are the same function and their parameters have a LUB.
let lub_ty = self
.commit_if_ok(|_| self.at(cause, self.param_env).lub(prev_ty, new_ty))
.map(|ok| self.register_infer_ok_obligations(ok));
if lub_ty.is_ok() {
// We have a LUB of prev_ty and new_ty, just return it.
return lub_ty;
// Function items or non-capturing closures of differing IDs or InternalSubsts.
let (a_sig, b_sig) = {
let is_capturing_closure = |ty| {
if let &ty::Closure(_, substs) = ty {
substs.as_closure().upvar_tys().next().is_some()
} else {
false
}
};
if is_capturing_closure(&prev_ty.kind) || is_capturing_closure(&new_ty.kind) {
(None, None)
} else {
match (&prev_ty.kind, &new_ty.kind) {
(&ty::FnDef(..), &ty::FnDef(..)) => {
// Don't reify if the function types have a LUB, i.e., they
// are the same function and their parameters have a LUB.
match self
.commit_if_ok(|_| self.at(cause, self.param_env).lub(prev_ty, new_ty))
{
// We have a LUB of prev_ty and new_ty, just return it.
Ok(ok) => return Ok(self.register_infer_ok_obligations(ok)),
Err(_) => {
(Some(prev_ty.fn_sig(self.tcx)), Some(new_ty.fn_sig(self.tcx)))
}
}
}
(&ty::Closure(_, substs), &ty::FnDef(..)) => {
let b_sig = new_ty.fn_sig(self.tcx);
let a_sig = self
.tcx
.signature_unclosure(substs.as_closure().sig(), b_sig.unsafety());
(Some(a_sig), Some(b_sig))
}
(&ty::FnDef(..), &ty::Closure(_, substs)) => {
let a_sig = prev_ty.fn_sig(self.tcx);
let b_sig = self
.tcx
.signature_unclosure(substs.as_closure().sig(), a_sig.unsafety());
(Some(a_sig), Some(b_sig))
}
(&ty::Closure(_, substs_a), &ty::Closure(_, substs_b)) => (
Some(self.tcx.signature_unclosure(
substs_a.as_closure().sig(),
hir::Unsafety::Normal,
)),
Some(self.tcx.signature_unclosure(
substs_b.as_closure().sig(),
hir::Unsafety::Normal,
)),
),
_ => (None, None),
}
}
};
if let (Some(a_sig), Some(b_sig)) = (a_sig, b_sig) {
// The signature must match.
let a_sig = prev_ty.fn_sig(self.tcx);
let a_sig = self.normalize_associated_types_in(new.span, &a_sig);
let b_sig = new_ty.fn_sig(self.tcx);
let b_sig = self.normalize_associated_types_in(new.span, &b_sig);
let sig = self
.at(cause, self.param_env)
@ -901,17 +942,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// Reify both sides and return the reified fn pointer type.
let fn_ptr = self.tcx.mk_fn_ptr(sig);
for expr in exprs.iter().map(|e| e.as_coercion_site()).chain(Some(new)) {
// The only adjustment that can produce an fn item is
// `NeverToAny`, so this should always be valid.
let prev_adjustment = match prev_ty.kind {
ty::Closure(..) => Adjust::Pointer(PointerCast::ClosureFnPointer(a_sig.unsafety())),
ty::FnDef(..) => Adjust::Pointer(PointerCast::ReifyFnPointer),
_ => unreachable!(),
};
let next_adjustment = match new_ty.kind {
ty::Closure(..) => Adjust::Pointer(PointerCast::ClosureFnPointer(b_sig.unsafety())),
ty::FnDef(..) => Adjust::Pointer(PointerCast::ReifyFnPointer),
_ => unreachable!(),
};
for expr in exprs.iter().map(|e| e.as_coercion_site()) {
self.apply_adjustments(
expr,
vec![Adjustment {
kind: Adjust::Pointer(PointerCast::ReifyFnPointer),
target: fn_ptr,
}],
vec![Adjustment { kind: prev_adjustment.clone(), target: fn_ptr }],
);
}
self.apply_adjustments(new, vec![Adjustment { kind: next_adjustment, target: fn_ptr }]);
return Ok(fn_ptr);
}