Auto merge of #65195 - varkor:to_option, r=<try>

Rename `bool::then_*` to `bool::to_option_*` and use where appropriate

Name change following rust-lang/rfcs#2757. Also try it out throughout the compiler in places I think makes the code more readable.

Author: bors

src/libcore/bool.rs

@@ -9,12 +9,12 @@ impl bool {
     /// ```
     /// #![feature(bool_to_option)]
     ///
-    /// assert_eq!(false.then(0), None);
-    /// assert_eq!(true.then(0), Some(0));
+    /// assert_eq!(false.to_option(0), None);
+    /// assert_eq!(true.to_option(0), Some(0));
     /// ```
     #[unstable(feature = "bool_to_option", issue = "64260")]
     #[inline]
-    pub fn then<T>(self, t: T) -> Option<T> {
+    pub fn to_option<T>(self, t: T) -> Option<T> {
         if self {
             Some(t)
         } else {
@@ -29,12 +29,12 @@ impl bool {
     /// ```
     /// #![feature(bool_to_option)]
     ///
-    /// assert_eq!(false.then_with(|| 0), None);
-    /// assert_eq!(true.then_with(|| 0), Some(0));
+    /// assert_eq!(false.to_option_with(|| 0), None);
+    /// assert_eq!(true.to_option_with(|| 0), Some(0));
     /// ```
     #[unstable(feature = "bool_to_option", issue = "64260")]
     #[inline]
-    pub fn then_with<T, F: FnOnce() -> T>(self, f: F) -> Option<T> {
+    pub fn to_option_with<T, F: FnOnce() -> T>(self, f: F) -> Option<T> {
         if self {
             Some(f())
         } else {

src/libcore/tests/bool.rs

@@ -1,7 +1,7 @@
 #[test]
 fn test_bool_to_option() {
-    assert_eq!(false.then(0), None);
-    assert_eq!(true.then(0), Some(0));
-    assert_eq!(false.then_with(|| 0), None);
-    assert_eq!(true.then_with(|| 0), Some(0));
+    assert_eq!(false.to_option(0), None);
+    assert_eq!(true.to_option(0), Some(0));
+    assert_eq!(false.to_option_with(|| 0), None);
+    assert_eq!(true.to_option_with(|| 0), Some(0));
 }

src/libfmt_macros/lib.rs

@@ -11,6 +11,7 @@
 #![feature(nll)]
 #![feature(rustc_private)]
 #![feature(unicode_internals)]
+#![feature(bool_to_option)]
 
 pub use Piece::*;
 pub use Position::*;
@@ -633,11 +634,7 @@ impl<'a> Parser<'a> {
                 break;
             }
         }
-        if found {
-            Some(cur)
-        } else {
-            None
-        }
+        found.to_option(cur)
     }
 }
 

src/librustc/hir/map/blocks.rs

@@ -147,13 +147,7 @@ impl<'a> FnLikeNode<'a> {
             map::Node::Expr(e) => e.is_fn_like(),
             _ => false
         };
-        if fn_like {
-            Some(FnLikeNode {
-                node,
-            })
-        } else {
-            None
-        }
+        fn_like.to_option(FnLikeNode { node })
     }
 
     pub fn body(self) -> ast::BodyId {

src/librustc/infer/outlives/verify.rs

@@ -211,11 +211,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
                 (r, p)
             );
             let p_ty = p.to_ty(tcx);
-            if compare_ty(p_ty) {
-                Some(ty::OutlivesPredicate(p_ty, r))
-            } else {
-                None
-            }
+            compare_ty(p_ty).to_option(ty::OutlivesPredicate(p_ty, r))
         });
 
         param_bounds

src/librustc/lib.rs

@@ -29,6 +29,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![feature(arbitrary_self_types)]
+#![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(const_fn)]

src/librustc/mir/mod.rs

@@ -305,11 +305,7 @@ impl<'tcx> Body<'tcx> {
     pub fn vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
         (self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
             let local = Local::new(index);
-            if self.local_decls[local].is_user_variable.is_some() {
-                Some(local)
-            } else {
-                None
-            }
+            self.local_decls[local].is_user_variable.as_ref().map(|_| local)
         })
     }
 

src/librustc/session/mod.rs

@@ -825,11 +825,7 @@ impl Session {
     }
 
     pub fn incr_comp_session_dir_opt(&self) -> Option<cell::Ref<'_, PathBuf>> {
-        if self.opts.incremental.is_some() {
-            Some(self.incr_comp_session_dir())
-        } else {
-            None
-        }
+        self.opts.incremental.as_ref().map(|_| self.incr_comp_session_dir())
     }
 
     pub fn print_perf_stats(&self) {
@@ -1148,8 +1144,9 @@ fn build_session_(
                     None
                 }
             }
-        }
-        else { None };
+        } else {
+            None
+        };
 
     let host_triple = TargetTriple::from_triple(config::host_triple());
     let host = Target::search(&host_triple).unwrap_or_else(|e|

src/librustc/traits/error_reporting.rs

@@ -340,11 +340,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             return None
         };
 
-        if tcx.has_attr(impl_def_id, sym::rustc_on_unimplemented) {
-            Some(impl_def_id)
-        } else {
-            None
-        }
+        tcx.has_attr(impl_def_id, sym::rustc_on_unimplemented).to_option(impl_def_id)
     }
 
     fn on_unimplemented_note(

src/librustc/ty/context.rs

@@ -1572,11 +1572,7 @@ 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() {
-                    Some(output)
-                } else {
-                    None
-                }
+                output.is_impl_trait().to_option(output)
             }
             _ => None
         }