hir: Two preparatory changes for #120206

compiler/rustc_ast_lowering/src/expr.rs

@@ -153,7 +153,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 }
                 ExprKind::Let(pat, scrutinee, span, is_recovered) => {
                     hir::ExprKind::Let(self.arena.alloc(hir::Let {
-                        hir_id: self.next_id(),
                         span: self.lower_span(*span),
                         pat: self.lower_pat(pat),
                         ty: None,

compiler/rustc_ast_lowering/src/lib.rs

@@ -2305,7 +2305,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         match c.value.kind {
             ExprKind::Underscore => {
                 if self.tcx.features().generic_arg_infer {
-                    hir::ArrayLen::Infer(self.lower_node_id(c.id), self.lower_span(c.value.span))
+                    hir::ArrayLen::Infer(hir::InferArg {
+                        hir_id: self.lower_node_id(c.id),
+                        span: self.lower_span(c.value.span),
+                    })
                 } else {
                     feature_err(
                         &self.tcx.sess,

compiler/rustc_hir/src/hir.rs

@@ -1273,7 +1273,6 @@ pub struct Arm<'hir> {
 /// desugaring to if-let. Only let-else supports the type annotation at present.
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
 pub struct Let<'hir> {
-    pub hir_id: HirId,
     pub span: Span,
     pub pat: &'hir Pat<'hir>,
     pub ty: Option<&'hir Ty<'hir>>,
@@ -1532,14 +1531,16 @@ pub type Lit = Spanned<LitKind>;
 
 #[derive(Copy, Clone, Debug, HashStable_Generic)]
 pub enum ArrayLen {
-    Infer(HirId, Span),
+    Infer(InferArg),
     Body(AnonConst),
 }
 
 impl ArrayLen {
     pub fn hir_id(&self) -> HirId {
         match self {
-            &ArrayLen::Infer(hir_id, _) | &ArrayLen::Body(AnonConst { hir_id, .. }) => hir_id,
+            ArrayLen::Infer(InferArg { hir_id, .. }) | ArrayLen::Body(AnonConst { hir_id, .. }) => {
+                *hir_id
+            }
         }
     }
 }
@@ -2424,7 +2425,7 @@ impl<'hir> Ty<'hir> {
             TyKind::Infer => true,
             TyKind::Slice(ty) => ty.is_suggestable_infer_ty(),
             TyKind::Array(ty, length) => {
-                ty.is_suggestable_infer_ty() || matches!(length, ArrayLen::Infer(_, _))
+                ty.is_suggestable_infer_ty() || matches!(length, ArrayLen::Infer(..))
             }
             TyKind::Tup(tys) => tys.iter().any(Self::is_suggestable_infer_ty),
             TyKind::Ptr(mut_ty) | TyKind::Ref(_, mut_ty) => mut_ty.ty.is_suggestable_infer_ty(),

compiler/rustc_hir/src/intravisit.rs

@@ -341,9 +341,6 @@ pub trait Visitor<'v>: Sized {
     fn visit_expr(&mut self, ex: &'v Expr<'v>) {
         walk_expr(self, ex)
     }
-    fn visit_let_expr(&mut self, lex: &'v Let<'v>) {
-        walk_let_expr(self, lex)
-    }
     fn visit_expr_field(&mut self, field: &'v ExprField<'v>) {
         walk_expr_field(self, field)
     }
@@ -672,7 +669,7 @@ pub fn walk_pat_field<'v, V: Visitor<'v>>(visitor: &mut V, field: &'v PatField<'
 
 pub fn walk_array_len<'v, V: Visitor<'v>>(visitor: &mut V, len: &'v ArrayLen) {
     match len {
-        &ArrayLen::Infer(hir_id, _span) => visitor.visit_id(hir_id),
+        ArrayLen::Infer(InferArg { hir_id, span: _ }) => visitor.visit_id(*hir_id),
         ArrayLen::Body(c) => visitor.visit_anon_const(c),
     }
 }
@@ -729,7 +726,12 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
         ExprKind::DropTemps(ref subexpression) => {
             visitor.visit_expr(subexpression);
         }
-        ExprKind::Let(ref let_expr) => visitor.visit_let_expr(let_expr),
+        ExprKind::Let(Let { span: _, pat, ty, init, is_recovered: _ }) => {
+            // match the visit order in walk_local
+            visitor.visit_expr(init);
+            visitor.visit_pat(pat);
+            walk_list!(visitor, visit_ty, ty);
+        }
         ExprKind::If(ref cond, ref then, ref else_opt) => {
             visitor.visit_expr(cond);
             visitor.visit_expr(then);
@@ -806,14 +808,6 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
     }
 }
 
-pub fn walk_let_expr<'v, V: Visitor<'v>>(visitor: &mut V, let_expr: &'v Let<'v>) {
-    // match the visit order in walk_local
-    visitor.visit_expr(let_expr.init);
-    visitor.visit_id(let_expr.hir_id);
-    visitor.visit_pat(let_expr.pat);
-    walk_list!(visitor, visit_ty, let_expr.ty);
-}
-
 pub fn walk_expr_field<'v, V: Visitor<'v>>(visitor: &mut V, field: &'v ExprField<'v>) {
     visitor.visit_id(field.hir_id);
     visitor.visit_ident(field.ident);

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2529,7 +2529,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             }
             hir::TyKind::Array(ty, length) => {
                 let length = match length {
-                    &hir::ArrayLen::Infer(_, span) => self.ct_infer(tcx.types.usize, None, span),
+                    hir::ArrayLen::Infer(inf) => self.ct_infer(tcx.types.usize, None, inf.span),
                     hir::ArrayLen::Body(constant) => {
                         ty::Const::from_anon_const(tcx, constant.def_id)
                     }

compiler/rustc_hir_analysis/src/collect.rs

@@ -146,8 +146,8 @@ impl<'v> Visitor<'v> for HirPlaceholderCollector {
         }
     }
     fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
-        if let &hir::ArrayLen::Infer(_, span) = length {
-            self.0.push(span);
+        if let hir::ArrayLen::Infer(inf) = length {
+            self.0.push(inf.span);
         }
         intravisit::walk_array_len(self, length)
     }

compiler/rustc_hir_pretty/src/lib.rs

@@ -956,7 +956,7 @@ impl<'a> State<'a> {
 
     fn print_array_length(&mut self, len: &hir::ArrayLen) {
         match len {
-            hir::ArrayLen::Infer(_, _) => self.word("_"),
+            hir::ArrayLen::Infer(..) => self.word("_"),
             hir::ArrayLen::Body(ct) => self.print_anon_const(ct),
         }
     }

compiler/rustc_hir_typeck/src/expr.rs

@@ -320,7 +320,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             ExprKind::Ret(ref expr_opt) => self.check_expr_return(expr_opt.as_deref(), expr),
             ExprKind::Become(call) => self.check_expr_become(call, expr),
-            ExprKind::Let(let_expr) => self.check_expr_let(let_expr),
+            ExprKind::Let(let_expr) => self.check_expr_let(let_expr, expr.hir_id),
             ExprKind::Loop(body, _, source, _) => {
                 self.check_expr_loop(body, source, expected, expr)
             }
@@ -1259,12 +1259,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>) -> Ty<'tcx> {
+    pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>, hir_id: HirId) -> Ty<'tcx> {
         // for let statements, this is done in check_stmt
         let init = let_expr.init;
         self.warn_if_unreachable(init.hir_id, init.span, "block in `let` expression");
         // otherwise check exactly as a let statement
-        self.check_decl(let_expr.into());
+        self.check_decl((let_expr, hir_id).into());
         // but return a bool, for this is a boolean expression
         if let Some(error_guaranteed) = let_expr.is_recovered {
             self.set_tainted_by_errors(error_guaranteed);

compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

@@ -405,7 +405,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     pub fn array_length_to_const(&self, length: &hir::ArrayLen) -> ty::Const<'tcx> {
         match length {
-            &hir::ArrayLen::Infer(_, span) => self.ct_infer(self.tcx.types.usize, None, span),
+            hir::ArrayLen::Infer(inf) => self.ct_infer(self.tcx.types.usize, None, inf.span),
             hir::ArrayLen::Body(anon_const) => {
                 let span = self.tcx.def_span(anon_const.def_id);
                 let c = ty::Const::from_anon_const(self.tcx, anon_const.def_id);

compiler/rustc_hir_typeck/src/gather_locals.rs

@@ -48,9 +48,9 @@ impl<'a> From<&'a hir::Local<'a>> for Declaration<'a> {
     }
 }
 
-impl<'a> From<&'a hir::Let<'a>> for Declaration<'a> {
-    fn from(let_expr: &'a hir::Let<'a>) -> Self {
-        let hir::Let { hir_id, pat, ty, span, init, is_recovered: _ } = *let_expr;
+impl<'a> From<(&'a hir::Let<'a>, hir::HirId)> for Declaration<'a> {
+    fn from((let_expr, hir_id): (&'a hir::Let<'a>, hir::HirId)) -> Self {
+        let hir::Let { pat, ty, span, init, is_recovered: _ } = *let_expr;
         Declaration { hir_id, pat, ty, span, init: Some(init), origin: DeclOrigin::LetExpr }
     }
 }
@@ -125,9 +125,11 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
         intravisit::walk_local(self, local)
     }
 
-    fn visit_let_expr(&mut self, let_expr: &'tcx hir::Let<'tcx>) {
-        self.declare(let_expr.into());
-        intravisit::walk_let_expr(self, let_expr);
+    fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
+        if let hir::ExprKind::Let(let_expr) = expr.kind {
+            self.declare((let_expr, expr.hir_id).into());
+        }
+        intravisit::walk_expr(self, expr)
     }
 
     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {

compiler/rustc_passes/src/hir_stats.rs

@@ -328,11 +328,6 @@ impl<'v> hir_visit::Visitor<'v> for StatCollector<'v> {
         hir_visit::walk_expr(self, e)
     }
 
-    fn visit_let_expr(&mut self, lex: &'v hir::Let<'v>) {
-        self.record("Let", Id::Node(lex.hir_id), lex);
-        hir_visit::walk_let_expr(self, lex)
-    }
-
     fn visit_expr_field(&mut self, f: &'v hir::ExprField<'v>) {
         self.record("ExprField", Id::Node(f.hir_id), f);
         hir_visit::walk_expr_field(self, f)

src/librustdoc/clean/mod.rs

@@ -1835,7 +1835,7 @@ pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> T
         TyKind::Slice(ty) => Slice(Box::new(clean_ty(ty, cx))),
         TyKind::Array(ty, ref length) => {
             let length = match length {
-                hir::ArrayLen::Infer(_, _) => "_".to_string(),
+                hir::ArrayLen::Infer(..) => "_".to_string(),
                 hir::ArrayLen::Body(anon_const) => {
                     // NOTE(min_const_generics): We can't use `const_eval_poly` for constants
                     // as we currently do not supply the parent generics to anonymous constants