Add new temporary lifetime feature gate and super let keyword

compiler/rustc_ast/src/ast.rs

@@ -1067,20 +1067,23 @@ pub enum LocalKind {
     /// Local declaration with an initializer and an `else` clause.
     /// Example: `let Some(x) = y else { return };`
     InitElse(P<Expr>, P<Block>),
+    /// Local declaration with an initializer living through the temporary lifetime.
+    /// Example: `super let x = y;`
+    Super(P<Expr>),
 }
 
 impl LocalKind {
     pub fn init(&self) -> Option<&Expr> {
         match self {
             Self::Decl => None,
-            Self::Init(i) | Self::InitElse(i, _) => Some(i),
+            Self::Init(i) | Self::InitElse(i, _) | Self::Super(i) => Some(i),
         }
     }
 
     pub fn init_else_opt(&self) -> Option<(&Expr, Option<&Block>)> {
         match self {
             Self::Decl => None,
-            Self::Init(init) => Some((init, None)),
+            Self::Init(init) | Self::Super(init) => Some((init, None)),
             Self::InitElse(init, els) => Some((init, Some(els))),
         }
     }

compiler/rustc_ast/src/mut_visit.rs

@@ -609,7 +609,7 @@ pub fn noop_visit_local<T: MutVisitor>(local: &mut P<Local>, vis: &mut T) {
     visit_opt(ty, |ty| vis.visit_ty(ty));
     match kind {
         LocalKind::Decl => {}
-        LocalKind::Init(init) => {
+        LocalKind::Init(init) | LocalKind::Super(init) => {
             vis.visit_expr(init);
         }
         LocalKind::InitElse(init, els) => {

compiler/rustc_ast_lowering/src/block.rs

@@ -97,7 +97,16 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let span = self.lower_span(l.span);
         let source = hir::LocalSource::Normal;
         self.lower_attrs(hir_id, &l.attrs);
-        self.arena.alloc(hir::Local { hir_id, ty, pat, init, els, span, source })
+        self.arena.alloc(hir::Local {
+            hir_id,
+            ty,
+            pat,
+            init,
+            els,
+            span,
+            source,
+            is_super: matches!(l.kind, LocalKind::Super(..)),
+        })
     }
 
     fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {

compiler/rustc_ast_lowering/src/lib.rs

@@ -2342,6 +2342,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             source,
             span: self.lower_span(span),
             ty: None,
+            is_super: false,
         };
         self.stmt(span, hir::StmtKind::Local(self.arena.alloc(local)))
     }

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1090,6 +1090,9 @@ impl<'a> State<'a> {
                 self.print_outer_attributes(&loc.attrs);
                 self.space_if_not_bol();
                 self.ibox(INDENT_UNIT);
+                if matches!(loc.kind, ast::LocalKind::Super(..)) {
+                    self.word_nbsp("super")
+                }
                 self.word_nbsp("let");
 
                 self.ibox(INDENT_UNIT);

compiler/rustc_feature/src/unstable.rs

@@ -537,6 +537,8 @@ declare_features! (
     (unstable, never_type, "1.13.0", Some(35121)),
     /// Allows diverging expressions to fall back to `!` rather than `()`.
     (unstable, never_type_fallback, "1.41.0", Some(65992)),
+    /// Allows new temporary lifetime rules
+    (unstable, new_temp_lifetime, "1.72.0", Some(99999)),
     /// Allows `#![no_core]`.
     (unstable, no_core, "1.3.0", Some(29639)),
     /// Allows the use of `no_sanitize` attribute.

compiler/rustc_hir/src/hir.rs

@@ -1232,6 +1232,7 @@ pub struct Local<'hir> {
     /// Else block for a `let...else` binding.
     pub els: Option<&'hir Block<'hir>>,
     pub hir_id: HirId,
+    pub is_super: bool,
     pub span: Span,
     /// Can be `ForLoopDesugar` if the `let` statement is part of a `for` loop
     /// desugaring. Otherwise will be `Normal`.

compiler/rustc_hir_analysis/src/check/mod.rs

@@ -70,6 +70,7 @@ mod errs;
 pub mod intrinsic;
 pub mod intrinsicck;
 mod region;
+mod scope_map;
 pub mod wfcheck;
 
 pub use check::check_abi;
@@ -105,6 +106,7 @@ use crate::util::common::indenter;
 
 use self::compare_impl_item::collect_return_position_impl_trait_in_trait_tys;
 use self::region::region_scope_tree;
+use self::scope_map::body_scope_map;
 
 pub fn provide(providers: &mut Providers) {
     wfcheck::provide(providers);
@@ -114,6 +116,7 @@ pub fn provide(providers: &mut Providers) {
         collect_return_position_impl_trait_in_trait_tys,
         compare_impl_const: compare_impl_item::compare_impl_const_raw,
         check_coroutine_obligations: check::check_coroutine_obligations,
+        body_scope_map,
         ..*providers
     };
 }