Rename confusing function name

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -992,7 +992,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             }
         }
 
-        if look_at_return && hir.get_return_block(closure_id).is_some() {
+        if look_at_return && hir.get_fn_id_for_return_block(closure_id).is_some() {
             // ...otherwise we are probably in the tail expression of the function, point at the
             // return type.
             match self.infcx.tcx.hir_node_by_def_id(hir.get_parent_item(fn_call_id).def_id) {

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -944,7 +944,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Option<(LocalDefId, &'tcx hir::FnDecl<'tcx>, bool)> {
         // Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
         // `while` before reaching it, as block tail returns are not available in them.
-        self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
+        self.tcx.hir().get_fn_id_for_return_block(blk_id).and_then(|blk_id| {
             let parent = self.tcx.hir_node(blk_id);
             self.get_node_fn_decl(parent)
                 .map(|(fn_id, fn_decl, _, is_main)| (fn_id, fn_decl, is_main))

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1909,7 +1909,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let returned = matches!(
             self.tcx.parent_hir_node(expr.hir_id),
             hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Ret(_), .. })
-        ) || map.get_return_block(expr.hir_id).is_some();
+        ) || map.get_fn_id_for_return_block(expr.hir_id).is_some();
         if returned
             && let ty::Adt(e, args_e) = expected.kind()
             && let ty::Adt(f, args_f) = found.kind()

compiler/rustc_middle/src/hir/map/mod.rs

@@ -511,14 +511,14 @@ impl<'hir> Map<'hir> {
         self.body_const_context(self.enclosing_body_owner(hir_id)).is_some()
     }
 
-    /// Retrieves the `HirId` for `id`'s enclosing method's body, unless there's a
-    /// `while` or `loop` before reaching it, as block tail returns are not
-    /// available in them.
+    /// Retrieves the `HirId` for `id`'s enclosing function *if* the `id` block or return is
+    /// in the "tail" position of the function, in other words if it's likely to correspond
+    /// to the return type of the function.
     ///
     /// ```
     /// fn foo(x: usize) -> bool {
     ///     if x == 1 {
-    ///         true  // If `get_return_block` gets passed the `id` corresponding
+    ///         true  // If `get_fn_id_for_return_block` gets passed the `id` corresponding
     ///     } else {  // to this, it will return `foo`'s `HirId`.
     ///         false
     ///     }
@@ -528,12 +528,12 @@ impl<'hir> Map<'hir> {
     /// ```compile_fail,E0308
     /// fn foo(x: usize) -> bool {
     ///     loop {
-    ///         true  // If `get_return_block` gets passed the `id` corresponding
+    ///         true  // If `get_fn_id_for_return_block` gets passed the `id` corresponding
     ///     }         // to this, it will return `None`.
     ///     false
     /// }
     /// ```
-    pub fn get_return_block(self, id: HirId) -> Option<HirId> {
+    pub fn get_fn_id_for_return_block(self, id: HirId) -> Option<HirId> {
         let mut iter = self.parent_iter(id).peekable();
         let mut ignore_tail = false;
         if let Node::Expr(Expr { kind: ExprKind::Ret(_), .. }) = self.tcx.hir_node(id) {