Rollup merge of #104732 - WaffleLapkin:from_def_idn't, r=compiler-errors

Refactor `ty::ClosureKind` related stuff

I've tried to fix all duplication and weirdness, but if I missed something do tell :p

r? `@compiler-errors`

4 files changed, 25 insertions, 35 deletions

diff --git a/compiler/rustc_middle/src/middle/lang_items.rs b/compiler/rustc_middle/src/middle/lang_items.rs
index dd4332d0db6..343ea1f00f5 100644
--- a/compiler/rustc_middle/src/middle/lang_items.rs
+++ b/compiler/rustc_middle/src/middle/lang_items.rs
@@ -27,7 +27,10 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn fn_trait_kind_from_lang_item(self, id: DefId) -> Option<ty::ClosureKind> {
+    /// Given a [`DefId`] of a [`Fn`], [`FnMut`] or [`FnOnce`] traits,
+    /// returns a corresponding [`ty::ClosureKind`].
+    /// For any other [`DefId`] return `None`.
+    pub fn fn_trait_kind_from_def_id(self, id: DefId) -> Option<ty::ClosureKind> {
         let items = self.lang_items();
         match Some(id) {
             x if x == items.fn_trait() => Some(ty::ClosureKind::Fn),
@@ -36,6 +39,11 @@ impl<'tcx> TyCtxt<'tcx> {
             _ => None,
         }
     }
+
+    /// Returns `true` if `id` is a `DefId` of [`Fn`], [`FnMut`] or [`FnOnce`] traits.
+    pub fn is_fn_trait(self, id: DefId) -> bool {
+        self.fn_trait_kind_from_def_id(id).is_some()
+    }
 }
 
 /// Returns `true` if the specified `lang_item` must be present for this
diff --git a/compiler/rustc_middle/src/ty/closure.rs b/compiler/rustc_middle/src/ty/closure.rs
index 921ffead521..d00553cbad1 100644
--- a/compiler/rustc_middle/src/ty/closure.rs
+++ b/compiler/rustc_middle/src/ty/closure.rs
@@ -97,39 +97,12 @@ impl<'tcx> ClosureKind {
     /// Returns `true` if a type that impls this closure kind
     /// must also implement `other`.
     pub fn extends(self, other: ty::ClosureKind) -> bool {
-        matches!(
-            (self, other),
-            (ClosureKind::Fn, ClosureKind::Fn)
-                | (ClosureKind::Fn, ClosureKind::FnMut)
-                | (ClosureKind::Fn, ClosureKind::FnOnce)
-                | (ClosureKind::FnMut, ClosureKind::FnMut)
-                | (ClosureKind::FnMut, ClosureKind::FnOnce)
-                | (ClosureKind::FnOnce, ClosureKind::FnOnce)
-        )
-    }
-
-    /// Returns the representative scalar type for this closure kind.
-    /// See `Ty::to_opt_closure_kind` for more details.
-    pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
-        match self {
-            ClosureKind::Fn => tcx.types.i8,
-            ClosureKind::FnMut => tcx.types.i16,
-            ClosureKind::FnOnce => tcx.types.i32,
-        }
-    }
-
-    pub fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ClosureKind> {
-        if Some(def_id) == tcx.lang_items().fn_once_trait() {
-            Some(ClosureKind::FnOnce)
-        } else if Some(def_id) == tcx.lang_items().fn_mut_trait() {
-            Some(ClosureKind::FnMut)
-        } else if Some(def_id) == tcx.lang_items().fn_trait() {
-            Some(ClosureKind::Fn)
-        } else {
-            None
-        }
+        self <= other
     }
 
+    /// Converts `self` to a [`DefId`] of the corresponding trait.
+    ///
+    /// Note: the inverse of this function is [`TyCtxt::fn_trait_kind_from_def_id`].
     pub fn to_def_id(&self, tcx: TyCtxt<'_>) -> DefId {
         tcx.require_lang_item(
             match self {
@@ -140,6 +113,16 @@ impl<'tcx> ClosureKind {
             None,
         )
     }
+
+    /// Returns the representative scalar type for this closure kind.
+    /// See `Ty::to_opt_closure_kind` for more details.
+    pub fn to_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
+        match self {
+            ClosureKind::Fn => tcx.types.i8,
+            ClosureKind::FnMut => tcx.types.i16,
+            ClosureKind::FnOnce => tcx.types.i32,
+        }
+    }
 }
 
 /// A composite describing a `Place` that is captured by a closure.
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 44b85098630..bd17f7d34ad 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1080,7 +1080,7 @@ pub trait PrettyPrinter<'tcx>:
                 let mut resugared = false;
 
                 // Special-case `Fn(...) -> ...` and re-sugar it.
-                let fn_trait_kind = cx.tcx().fn_trait_kind_from_lang_item(principal.def_id);
+                let fn_trait_kind = cx.tcx().fn_trait_kind_from_def_id(principal.def_id);
                 if !cx.should_print_verbose() && fn_trait_kind.is_some() {
                     if let ty::Tuple(tys) = principal.substs.type_at(0).kind() {
                         let mut projections = predicates.projection_bounds();
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 1e1a566de44..5984686044b 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -2116,8 +2116,7 @@ impl<'tcx> Ty<'tcx> {
     /// parameter. This is kind of a phantom type, except that the
     /// most convenient thing for us to are the integral types. This
     /// function converts such a special type into the closure
-    /// kind. To go the other way, use
-    /// `tcx.closure_kind_ty(closure_kind)`.
+    /// kind. To go the other way, use `closure_kind.to_ty(tcx)`.
     ///
     /// Note that during type checking, we use an inference variable
     /// to represent the closure kind, because it has not yet been