Add support for ExprKind::Use

Introduced in rust-lang/rust#60225

Author: Manishearth

clippy_lints/src/loops.rs

@@ -671,6 +671,7 @@ fn never_loop_expr(expr: &Expr, main_loop_id: HirId) -> NeverLoopResult {
     match expr.node {
         ExprKind::Box(ref e)
         | ExprKind::Unary(_, ref e)
+        | ExprKind::Use(ref e)
         | ExprKind::Cast(ref e, _)
         | ExprKind::Type(ref e, _)
         | ExprKind::Field(ref e, _)

clippy_lints/src/utils/author.rs

@@ -492,6 +492,12 @@ impl<'tcx> Visitor<'tcx> for PrintVisitor {
                 self.current = value_pat;
                 self.visit_expr(value);
             },
+            ExprKind::Use(ref inner) => {
+                let inner_pat = self.next("inner");
+                println!("Use(ref {}) = {};", inner_pat, current);
+                self.current = inner_pat;
+                self.visit_expr(inner);
+            }
             ExprKind::Err => {
                 println!("Err = {}", current);
             },

clippy_lints/src/utils/higher.rs

@@ -184,6 +184,7 @@ pub fn is_from_for_desugar(local: &hir::Local) -> bool {
 /// `for pat in arg { body }` becomes `(pat, arg, body)`.
 pub fn for_loop(expr: &hir::Expr) -> Option<(&hir::Pat, &hir::Expr, &hir::Expr)> {
     if_chain! {
+        if let hir::ExprKind::Use(ref expr) = expr.node;
         if let hir::ExprKind::Match(ref iterexpr, ref arms, hir::MatchSource::ForLoopDesugar) = expr.node;
         if let hir::ExprKind::Call(_, ref iterargs) = iterexpr.node;
         if iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none();

clippy_lints/src/utils/hir_utils.rs

@@ -101,6 +101,7 @@ impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
                     && both(le, re, |l, r| self.eq_expr(l, r))
             },
             (&ExprKind::Box(ref l), &ExprKind::Box(ref r)) => self.eq_expr(l, r),
+            (&ExprKind::Use(ref l), &ExprKind::Use(ref r)) => self.eq_expr(l, r),
             (&ExprKind::Call(ref l_fun, ref l_args), &ExprKind::Call(ref r_fun, ref r_args)) => {
                 !self.ignore_fn && self.eq_expr(l_fun, r_fun) && self.eq_exprs(l_args, r_args)
             },
@@ -454,6 +455,11 @@ impl<'a, 'tcx: 'a> SpanlessHash<'a, 'tcx> {
                 c.hash(&mut self.s);
                 self.hash_expr(e);
             },
+            ExprKind::Use(ref e) => {
+                let c: fn(_) -> _ = ExprKind::Use;
+                c.hash(&mut self.s);
+                self.hash_expr(e);
+            },
             ExprKind::Call(ref fun, ref args) => {
                 let c: fn(_, _) -> _ = ExprKind::Call;
                 c.hash(&mut self.s);

clippy_lints/src/utils/inspector.rs

@@ -154,6 +154,10 @@ fn print_expr(cx: &LateContext<'_, '_>, expr: &hir::Expr, indent: usize) {
             println!("{}Box", ind);
             print_expr(cx, e, indent + 1);
         },
+        hir::ExprKind::Use(ref e) => {
+            println!("{}Use", ind);
+            print_expr(cx, e, indent + 1);
+        },
         hir::ExprKind::Array(ref v) => {
             println!("{}Array", ind);
             for e in v {

clippy_lints/src/utils/sugg.rs

@@ -93,6 +93,7 @@ impl<'a> Sugg<'a> {
         match expr.node {
             hir::ExprKind::AddrOf(..)
             | hir::ExprKind::Box(..)
+            | hir::ExprKind::Use(..)
             | hir::ExprKind::Closure(.., _)
             | hir::ExprKind::If(..)
             | hir::ExprKind::Unary(..)

tests/ui/author/for_loop.stdout

@@ -1,8 +1,6 @@
 if_chain! {
-    if let ExprKind::Block(ref block) = expr.node;
-    if let StmtKind::Local(ref local) = block.node;
-    if let Some(ref init) = local.init;
-    if let ExprKind::Match(ref expr, ref arms, MatchSource::ForLoopDesugar) = init.node;
+    if let ExprKind::Use(ref inner) = expr.node;
+    if let ExprKind::Match(ref expr, ref arms, MatchSource::ForLoopDesugar) = inner.node;
     if let ExprKind::Call(ref func, ref args) = expr.node;
     if let ExprKind::Path(ref path) = func.node;
     if match_qpath(path, &["{{root}}", "std", "iter", "IntoIterator", "into_iter"]);
@@ -13,17 +11,17 @@ if_chain! {
     // unimplemented: field checks
     if arms.len() == 1;
     if let ExprKind::Loop(ref body, ref label, LoopSource::ForLoop) = arms[0].body.node;
-    if let StmtKind::Local(ref local1) = body.node;
-    if let PatKind::Binding(BindingAnnotation::Mutable, _, name, None) = local1.pat.node;
+    if let StmtKind::Local(ref local) = body.node;
+    if let PatKind::Binding(BindingAnnotation::Mutable, _, name, None) = local.pat.node;
     if name.node.as_str() == "__next";
-    if let StmtKind::Expr(ref e, _) = local1.pat.node
+    if let StmtKind::Expr(ref e, _) = local.pat.node
     if let ExprKind::Match(ref expr1, ref arms1, MatchSource::ForLoopDesugar) = e.node;
     if let ExprKind::Call(ref func1, ref args1) = expr1.node;
     if let ExprKind::Path(ref path2) = func1.node;
     if match_qpath(path2, &["{{root}}", "std", "iter", "Iterator", "next"]);
     if args1.len() == 1;
-    if let ExprKind::AddrOf(MutMutable, ref inner) = args1[0].node;
-    if let ExprKind::Path(ref path3) = inner.node;
+    if let ExprKind::AddrOf(MutMutable, ref inner1) = args1[0].node;
+    if let ExprKind::Path(ref path3) = inner1.node;
     if match_qpath(path3, &["iter"]);
     if arms1.len() == 2;
     if let ExprKind::Assign(ref target, ref value) = arms1[0].body.node;
@@ -40,27 +38,23 @@ if_chain! {
     if arms1[1].pats.len() == 1;
     if let PatKind::Path(ref path7) = arms1[1].pats[0].node;
     if match_qpath(path7, &["{{root}}", "std", "option", "Option", "None"]);
-    if let StmtKind::Local(ref local2) = path7.node;
-    if let Some(ref init1) = local2.init;
-    if let ExprKind::Path(ref path8) = init1.node;
+    if let StmtKind::Local(ref local1) = path7.node;
+    if let Some(ref init) = local1.init;
+    if let ExprKind::Path(ref path8) = init.node;
     if match_qpath(path8, &["__next"]);
-    if let PatKind::Binding(BindingAnnotation::Unannotated, _, name1, None) = local2.pat.node;
+    if let PatKind::Binding(BindingAnnotation::Unannotated, _, name1, None) = local1.pat.node;
     if name1.node.as_str() == "y";
-    if let StmtKind::Expr(ref e1, _) = local2.pat.node
-    if let ExprKind::Block(ref block1) = e1.node;
-    if let StmtKind::Local(ref local3) = block1.node;
-    if let Some(ref init2) = local3.init;
-    if let ExprKind::Path(ref path9) = init2.node;
+    if let StmtKind::Expr(ref e1, _) = local1.pat.node
+    if let ExprKind::Block(ref block) = e1.node;
+    if let StmtKind::Local(ref local2) = block.node;
+    if let Some(ref init1) = local2.init;
+    if let ExprKind::Path(ref path9) = init1.node;
     if match_qpath(path9, &["y"]);
-    if let PatKind::Binding(BindingAnnotation::Unannotated, _, name2, None) = local3.pat.node;
+    if let PatKind::Binding(BindingAnnotation::Unannotated, _, name2, None) = local2.pat.node;
     if name2.node.as_str() == "z";
     if arms[0].pats.len() == 1;
     if let PatKind::Binding(BindingAnnotation::Mutable, _, name3, None) = arms[0].pats[0].node;
     if name3.node.as_str() == "iter";
-    if let PatKind::Binding(BindingAnnotation::Unannotated, _, name4, None) = local.pat.node;
-    if name4.node.as_str() == "_result";
-    if let ExprKind::Path(ref path10) = local.pat.node;
-    if match_qpath(path10, &["_result"]);
     then {
         // report your lint here
     }