`if $c:expr { Some($r:expr) } else { None }` =>> `$c.then(|| $r)`

4 files changed, 21 insertions, 27 deletions

diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index ba93330d581..2eafc356dc3 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -1062,7 +1062,7 @@ impl<'hir> Map<'hir> {
     }
 
     pub fn span_if_local(self, id: DefId) -> Option<Span> {
-        if id.is_local() { Some(self.tcx.def_span(id)) } else { None }
+        id.is_local().then(|| self.tcx.def_span(id))
     }
 
     pub fn res_span(self, res: Res) -> Option<Span> {
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 4aef071cd98..ba8b58e4480 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -1113,13 +1113,11 @@ impl<'tcx> TyCtxt<'tcx> {
             ty::FnDef(_, _) => {
                 let sig = ret_ty.fn_sig(self);
                 let output = self.erase_late_bound_regions(sig.output());
-                if output.is_impl_trait() {
+                output.is_impl_trait().then(|| {
                     let hir_id = self.hir().local_def_id_to_hir_id(scope_def_id);
                     let fn_decl = self.hir().fn_decl_by_hir_id(hir_id).unwrap();
-                    Some((output, fn_decl.output.span()))
-                } else {
-                    None
-                }
+                    (output, fn_decl.output.span())
+                })
             }
             _ => None,
         }
@@ -1225,13 +1223,12 @@ macro_rules! nop_lift {
         impl<'a, 'tcx> Lift<'tcx> for $ty {
             type Lifted = $lifted;
             fn lift_to_tcx(self, tcx: TyCtxt<'tcx>) -> Option<Self::Lifted> {
-                if tcx.interners.$set.contains_pointer_to(&InternedInSet(&*self.0.0)) {
+                tcx.interners
+                    .$set
+                    .contains_pointer_to(&InternedInSet(&*self.0.0))
                     // SAFETY: `self` is interned and therefore valid
                     // for the entire lifetime of the `TyCtxt`.
-                    Some(unsafe { mem::transmute(self) })
-                } else {
-                    None
-                }
+                    .then(|| unsafe { mem::transmute(self) })
             }
         }
     };
@@ -1246,13 +1243,13 @@ impl<'a, 'tcx> Lift<'tcx> for &'a List<Ty<'a>> {
         if self.is_empty() {
             return Some(List::empty());
         }
-        if tcx.interners.substs.contains_pointer_to(&InternedInSet(self.as_substs())) {
+
+        tcx.interners
+            .substs
+            .contains_pointer_to(&InternedInSet(self.as_substs()))
             // SAFETY: `self` is interned and therefore valid
             // for the entire lifetime of the `TyCtxt`.
-            Some(unsafe { mem::transmute::<&'a List<Ty<'a>>, &'tcx List<Ty<'tcx>>>(self) })
-        } else {
-            None
-        }
+            .then(|| unsafe { mem::transmute::<&'a List<Ty<'a>>, &'tcx List<Ty<'tcx>>>(self) })
     }
 }
 
@@ -1264,11 +1261,10 @@ macro_rules! nop_list_lift {
                 if self.is_empty() {
                     return Some(List::empty());
                 }
-                if tcx.interners.$set.contains_pointer_to(&InternedInSet(self)) {
-                    Some(unsafe { mem::transmute(self) })
-                } else {
-                    None
-                }
+                tcx.interners
+                    .$set
+                    .contains_pointer_to(&InternedInSet(self))
+                    .then(|| unsafe { mem::transmute(self) })
             }
         }
     };
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index 55f2395e531..1464199a60a 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -584,7 +584,7 @@ impl<'tcx> Instance<'tcx> {
     /// this function returns `None`, then the MIR body does not require substitution during
     /// codegen.
     fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
-        if self.def.has_polymorphic_mir_body() { Some(self.substs) } else { None }
+        self.def.has_polymorphic_mir_body().then(|| self.substs)
     }
 
     pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: &T) -> T
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index a6ab7440c8e..6b4a6a17aef 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -267,13 +267,11 @@ pub type SubstsRef<'tcx> = &'tcx InternalSubsts<'tcx>;
 impl<'tcx> InternalSubsts<'tcx> {
     /// Checks whether all elements of this list are types, if so, transmute.
     pub fn try_as_type_list(&'tcx self) -> Option<&'tcx List<Ty<'tcx>>> {
-        if self.iter().all(|arg| matches!(arg.unpack(), GenericArgKind::Type(_))) {
+        self.iter().all(|arg| matches!(arg.unpack(), GenericArgKind::Type(_))).then(|| {
             assert_eq!(TYPE_TAG, 0);
             // SAFETY: All elements are types, see `List<Ty<'tcx>>::as_substs`.
-            Some(unsafe { &*(self as *const List<GenericArg<'tcx>> as *const List<Ty<'tcx>>) })
-        } else {
-            None
-        }
+            unsafe { &*(self as *const List<GenericArg<'tcx>> as *const List<Ty<'tcx>>) }
+        })
     }
 
     /// Interpret these substitutions as the substitutions of a closure type.