Rollup merge of rust-lang#122776 - GuillaumeGomez:rename-hir-let, r=oli-obk

Rename `hir::Let` into `hir::LetExpr`

As discussed on [zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Improve.20naming.20of.20.60ExprKind.3A.3ALet.60.3F).

r? `````@Zalathar`````

Author: jhpratt

compiler/rustc_ast_lowering/src/expr.rs

@@ -157,7 +157,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     hir::ExprKind::AddrOf(*k, *m, ohs)
                 }
                 ExprKind::Let(pat, scrutinee, span, is_recovered) => {
-                    hir::ExprKind::Let(self.arena.alloc(hir::Let {
+                    hir::ExprKind::Let(self.arena.alloc(hir::LetExpr {
                         span: self.lower_span(*span),
                         pat: self.lower_pat(pat),
                         ty: None,

compiler/rustc_hir/src/hir.rs

@@ -1259,7 +1259,7 @@ pub struct Arm<'hir> {
 /// In an `if let`, imagine it as `if (let <pat> = <expr>) { ... }`; in a let-else, it is part of
 /// the desugaring to if-let. Only let-else supports the type annotation at present.
 #[derive(Debug, Clone, Copy, HashStable_Generic)]
-pub struct Let<'hir> {
+pub struct LetExpr<'hir> {
     pub span: Span,
     pub pat: &'hir Pat<'hir>,
     pub ty: Option<&'hir Ty<'hir>>,
@@ -1852,7 +1852,7 @@ pub enum ExprKind<'hir> {
     ///
     /// These are not `Local` and only occur as expressions.
     /// The `let Some(x) = foo()` in `if let Some(x) = foo()` is an example of `Let(..)`.
-    Let(&'hir Let<'hir>),
+    Let(&'hir LetExpr<'hir>),
     /// An `if` block, with an optional else block.
     ///
     /// I.e., `if <expr> { <expr> } else { <expr> }`.

compiler/rustc_hir/src/intravisit.rs

@@ -753,7 +753,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr<'v>)
         ExprKind::DropTemps(ref subexpression) => {
             try_visit!(visitor.visit_expr(subexpression));
         }
-        ExprKind::Let(Let { span: _, pat, ty, init, is_recovered: _ }) => {
+        ExprKind::Let(LetExpr { span: _, pat, ty, init, is_recovered: _ }) => {
             // match the visit order in walk_local
             try_visit!(visitor.visit_expr(init));
             try_visit!(visitor.visit_pat(pat));

compiler/rustc_hir_pretty/src/lib.rs

@@ -1387,7 +1387,7 @@ impl<'a> State<'a> {
                 // Print `}`:
                 self.bclose_maybe_open(expr.span, true);
             }
-            hir::ExprKind::Let(&hir::Let { pat, ty, init, .. }) => {
+            hir::ExprKind::Let(&hir::LetExpr { pat, ty, init, .. }) => {
                 self.print_let(pat, ty, init);
             }
             hir::ExprKind::If(test, blk, elseopt) => {

compiler/rustc_hir_typeck/src/_match.rs

@@ -317,7 +317,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.note("`if` expressions without `else` evaluate to `()`");
         err.help("consider adding an `else` block that evaluates to the expected type");
         *error = true;
-        if let ExprKind::Let(hir::Let { span, pat, init, .. }) = cond_expr.kind
+        if let ExprKind::Let(hir::LetExpr { span, pat, init, .. }) = cond_expr.kind
             && let ExprKind::Block(block, _) = then_expr.kind
             // Refutability checks occur on the MIR, so we approximate it here by checking
             // if we have an enum with a single variant or a struct in the pattern.

compiler/rustc_hir_typeck/src/expr.rs

@@ -1261,7 +1261,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    pub(super) fn check_expr_let(&self, let_expr: &'tcx hir::Let<'tcx>, hir_id: HirId) -> Ty<'tcx> {
+    pub(super) fn check_expr_let(
+        &self,
+        let_expr: &'tcx hir::LetExpr<'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");

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -245,7 +245,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                 }
             }
 
-            hir::ExprKind::Let(hir::Let { pat, init, .. }) => {
+            hir::ExprKind::Let(hir::LetExpr { pat, init, .. }) => {
                 self.walk_local(init, pat, None, |t| t.borrow_expr(init, ty::ImmBorrow))
             }
 

compiler/rustc_hir_typeck/src/gather_locals.rs

@@ -29,7 +29,7 @@ impl<'a> DeclOrigin<'a> {
     }
 }
 
-/// A declaration is an abstraction of [hir::Local] and [hir::Let].
+/// A declaration is an abstraction of [hir::Local] and [hir::LetExpr].
 ///
 /// It must have a hir_id, as this is how we connect gather_locals to the check functions.
 pub(super) struct Declaration<'a> {
@@ -48,9 +48,9 @@ impl<'a> From<&'a hir::Local<'a>> for Declaration<'a> {
     }
 }
 
-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;
+impl<'a> From<(&'a hir::LetExpr<'a>, hir::HirId)> for Declaration<'a> {
+    fn from((let_expr, hir_id): (&'a hir::LetExpr<'a>, hir::HirId)) -> Self {
+        let hir::LetExpr { pat, ty, span, init, is_recovered: _ } = *let_expr;
         Declaration { hir_id, pat, ty, span, init: Some(init), origin: DeclOrigin::LetExpr }
     }
 }

src/tools/clippy/clippy_lints/src/pattern_type_mismatch.rs

@@ -1,5 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use rustc_hir::{intravisit, Body, Expr, ExprKind, FnDecl, Let, LocalSource, Mutability, Pat, PatKind, Stmt, StmtKind};
+use rustc_hir::{intravisit, Body, Expr, ExprKind, FnDecl, LetExpr, LocalSource, Mutability, Pat, PatKind, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty;
@@ -103,7 +103,7 @@ impl<'tcx> LateLintPass<'tcx> for PatternTypeMismatch {
                 }
             }
         }
-        if let ExprKind::Let(Let { pat, .. }) = expr.kind {
+        if let ExprKind::Let(LetExpr { pat, .. }) = expr.kind {
             apply_lint(cx, pat, DerefPossible::Possible);
         }
     }

src/tools/clippy/clippy_lints/src/shadow.rs

@@ -5,7 +5,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::hir_id::ItemLocalId;
-use rustc_hir::{Block, Body, BodyOwnerKind, Expr, ExprKind, HirId, Let, Node, Pat, PatKind, QPath, UnOp};
+use rustc_hir::{Block, Body, BodyOwnerKind, Expr, ExprKind, HirId, LetExpr, Node, Pat, PatKind, QPath, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
 use rustc_span::{Span, Symbol};
@@ -238,7 +238,7 @@ fn find_init<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Option<&'tcx Expr<'
         let init = match node {
             Node::Arm(_) | Node::Pat(_) => continue,
             Node::Expr(expr) => match expr.kind {
-                ExprKind::Match(e, _, _) | ExprKind::Let(&Let { init: e, .. }) => Some(e),
+                ExprKind::Match(e, _, _) | ExprKind::Let(&LetExpr { init: e, .. }) => Some(e),
                 _ => None,
             },
             Node::Local(local) => local.init,