Rollup merge of #122487 - GuillaumeGomez:rename-stmtkind-local, r=oli-obk

Rename `StmtKind::Local` variant into `StmtKind::Let`

It comes from this [discussion](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Improve.20naming.20of.20.60ExprKind.3A.3ALet.60.3F).

Starting point was:

> I often end up looking at [ExprKind::Let](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_hir/enum.ExprKind.html#variant.Let) instead of Local because of the name. I think renaming it (both the `ExprKind` variant and the Let struct) to `LetPattern` or LetPat could improve the situation as I'm not sure I'm not the only one encountering this issue.

And then it evolved into:

> It's already `Expr::Let` instead of `StmtKind::Local`. Counterproposal: rename `StmtKind::Local` to `StmtKind::Let`.

The goal here is to clear this confusion.

r? `@oli-obk`

Author: matthiaskrgr

compiler/rustc_ast/src/ast.rs

@@ -1021,7 +1021,7 @@ impl Stmt {
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum StmtKind {
     /// A local (let) binding.
-    Local(P<Local>),
+    Let(P<Local>),
     /// An item definition.
     Item(P<Item>),
     /// Expr without trailing semi-colon.

compiler/rustc_ast/src/ast_traits.rs

@@ -182,7 +182,7 @@ impl<T: HasTokens> HasTokens for Option<T> {
 impl HasTokens for StmtKind {
     fn tokens(&self) -> Option<&LazyAttrTokenStream> {
         match self {
-            StmtKind::Local(local) => local.tokens.as_ref(),
+            StmtKind::Let(local) => local.tokens.as_ref(),
             StmtKind::Item(item) => item.tokens(),
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.tokens(),
             StmtKind::Empty => return None,
@@ -191,7 +191,7 @@ impl HasTokens for StmtKind {
     }
     fn tokens_mut(&mut self) -> Option<&mut Option<LazyAttrTokenStream>> {
         match self {
-            StmtKind::Local(local) => Some(&mut local.tokens),
+            StmtKind::Let(local) => Some(&mut local.tokens),
             StmtKind::Item(item) => item.tokens_mut(),
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.tokens_mut(),
             StmtKind::Empty => return None,
@@ -355,7 +355,7 @@ impl HasAttrs for StmtKind {
 
     fn attrs(&self) -> &[Attribute] {
         match self {
-            StmtKind::Local(local) => &local.attrs,
+            StmtKind::Let(local) => &local.attrs,
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.attrs(),
             StmtKind::Item(item) => item.attrs(),
             StmtKind::Empty => &[],
@@ -365,7 +365,7 @@ impl HasAttrs for StmtKind {
 
     fn visit_attrs(&mut self, f: impl FnOnce(&mut AttrVec)) {
         match self {
-            StmtKind::Local(local) => f(&mut local.attrs),
+            StmtKind::Let(local) => f(&mut local.attrs),
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => expr.visit_attrs(f),
             StmtKind::Item(item) => item.visit_attrs(f),
             StmtKind::Empty => {}

compiler/rustc_ast/src/mut_visit.rs

@@ -1567,7 +1567,7 @@ pub fn noop_flat_map_stmt_kind<T: MutVisitor>(
     vis: &mut T,
 ) -> SmallVec<[StmtKind; 1]> {
     match kind {
-        StmtKind::Local(mut local) => smallvec![StmtKind::Local({
+        StmtKind::Let(mut local) => smallvec![StmtKind::Let({
             vis.visit_local(&mut local);
             local
         })],

compiler/rustc_ast/src/visit.rs

@@ -787,7 +787,7 @@ pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) -> V::R
 
 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) -> V::Result {
     match &statement.kind {
-        StmtKind::Local(local) => try_visit!(visitor.visit_local(local)),
+        StmtKind::Let(local) => try_visit!(visitor.visit_local(local)),
         StmtKind::Item(item) => try_visit!(visitor.visit_item(item)),
         StmtKind::Expr(expr) | StmtKind::Semi(expr) => try_visit!(visitor.visit_expr(expr)),
         StmtKind::Empty => {}

compiler/rustc_ast_lowering/src/block.rs

@@ -32,11 +32,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut expr = None;
         while let [s, tail @ ..] = ast_stmts {
             match &s.kind {
-                StmtKind::Local(local) => {
+                StmtKind::Let(local) => {
                     let hir_id = self.lower_node_id(s.id);
                     let local = self.lower_local(local);
                     self.alias_attrs(hir_id, local.hir_id);
-                    let kind = hir::StmtKind::Local(local);
+                    let kind = hir::StmtKind::Let(local);
                     let span = self.lower_span(s.span);
                     stmts.push(hir::Stmt { hir_id, kind, span });
                 }

compiler/rustc_ast_lowering/src/lib.rs

@@ -2356,7 +2356,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             span: self.lower_span(span),
             ty: None,
         };
-        self.stmt(span, hir::StmtKind::Local(self.arena.alloc(local)))
+        self.stmt(span, hir::StmtKind::Let(self.arena.alloc(local)))
     }
 
     fn block_expr(&mut self, expr: &'hir hir::Expr<'hir>) -> &'hir hir::Block<'hir> {

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1212,7 +1212,7 @@ impl<'a> State<'a> {
     fn print_stmt(&mut self, st: &ast::Stmt) {
         self.maybe_print_comment(st.span.lo());
         match &st.kind {
-            ast::StmtKind::Local(loc) => {
+            ast::StmtKind::Let(loc) => {
                 self.print_outer_attributes(&loc.attrs);
                 self.space_if_not_bol();
                 self.ibox(INDENT_UNIT);

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -616,7 +616,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
                     // FIXME: We make sure that this is a normal top-level binding,
                     // but we could suggest `todo!()` for all uninitalized bindings in the pattern pattern
-                    if let hir::StmtKind::Local(hir::Local { span, ty, init: None, pat, .. }) =
+                    if let hir::StmtKind::Let(hir::Local { span, ty, init: None, pat, .. }) =
                         &ex.kind
                         && let hir::PatKind::Binding(..) = pat.kind
                         && span.contains(self.decl_span)

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -558,7 +558,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     hir::intravisit::walk_stmt(self, stmt);
                     let expr = match stmt.kind {
                         hir::StmtKind::Semi(expr) | hir::StmtKind::Expr(expr) => expr,
-                        hir::StmtKind::Local(hir::Local { init: Some(expr), .. }) => expr,
+                        hir::StmtKind::Let(hir::Local { init: Some(expr), .. }) => expr,
                         _ => {
                             return;
                         }
@@ -1305,7 +1305,7 @@ struct BindingFinder {
 impl<'tcx> Visitor<'tcx> for BindingFinder {
     type Result = ControlFlow<hir::HirId>;
     fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) -> Self::Result {
-        if let hir::StmtKind::Local(local) = s.kind
+        if let hir::StmtKind::Let(local) = s.kind
             && local.pat.span == self.span
         {
             ControlFlow::Break(local.hir_id)

compiler/rustc_expand/src/build.rs

@@ -218,7 +218,7 @@ impl<'a> ExtCtxt<'a> {
     }
 
     pub fn stmt_local(&self, local: P<ast::Local>, span: Span) -> ast::Stmt {
-        ast::Stmt { id: ast::DUMMY_NODE_ID, kind: ast::StmtKind::Local(local), span }
+        ast::Stmt { id: ast::DUMMY_NODE_ID, kind: ast::StmtKind::Let(local), span }
     }
 
     pub fn stmt_item(&self, sp: Span, item: P<ast::Item>) -> ast::Stmt {