X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=clippy_utils%2Fsrc%2Flib.rs;h=7f5a1bf9c0741707f0e4e34a66cb0fb6a6e199d7;hb=9fc4b92eb2831b5175a4720aff593252a716a2fa;hp=40d7963a5e545152d0e7ebb0be5e1b782509187f;hpb=588367b62ec0e6c30cb8d8783644775742da91fc;p=rust.git

diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 40d7963a5e5..7f5a1bf9c07 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -18,6 +18,7 @@
 extern crate rustc_ast;
 extern crate rustc_ast_pretty;
 extern crate rustc_attr;
+extern crate rustc_const_eval;
 extern crate rustc_data_structures;
 extern crate rustc_errors;
 extern crate rustc_hir;
@@ -25,7 +26,6 @@
 extern crate rustc_lexer;
 extern crate rustc_lint;
 extern crate rustc_middle;
-extern crate rustc_mir;
 extern crate rustc_session;
 extern crate rustc_span;
 extern crate rustc_target;
@@ -70,7 +70,7 @@
 use rustc_hir::def_id::DefId;
 use rustc_hir::hir_id::{HirIdMap, HirIdSet};
 use rustc_hir::intravisit::{self, walk_expr, ErasedMap, FnKind, NestedVisitorMap, Visitor};
-use rustc_hir::LangItem::{ResultErr, ResultOk};
+use rustc_hir::LangItem::{OptionNone, ResultErr, ResultOk};
 use rustc_hir::{
     def, Arm, BindingAnnotation, Block, Body, Constness, Destination, Expr, ExprKind, FnDecl, GenericArgs, HirId, Impl,
     ImplItem, ImplItemKind, IsAsync, Item, ItemKind, LangItem, Local, MatchSource, Mutability, Node, Param, Pat,
@@ -520,7 +520,7 @@ macro_rules! try_res {
             }
         };
     }
-    fn item_child_by_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, name: &str) -> Option<&'tcx Export<HirId>> {
+    fn item_child_by_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, name: &str) -> Option<&'tcx Export> {
         tcx.item_children(def_id)
             .iter()
             .find(|item| item.ident.name.as_str() == name)
@@ -557,7 +557,7 @@ fn item_child_by_name<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, name: &str) -> Opt
                 None
             }
         });
-    try_res!(last).res
+    try_res!(last).res.expect_non_local()
 }
 
 /// Convenience function to get the `DefId` of a trait by path.
@@ -644,6 +644,65 @@ pub fn can_mut_borrow_both(cx: &LateContext<'_>, e1: &Expr<'_>, e2: &Expr<'_>) -
     false
 }
 
+/// Returns true if the `def_id` associated with the `path` is recognized as a "default-equivalent"
+/// constructor from the std library
+fn is_default_equivalent_ctor(cx: &LateContext<'_>, def_id: DefId, path: &QPath<'_>) -> bool {
+    let std_types_symbols = &[
+        sym::string_type,
+        sym::vec_type,
+        sym::vecdeque_type,
+        sym::LinkedList,
+        sym::hashmap_type,
+        sym::BTreeMap,
+        sym::hashset_type,
+        sym::BTreeSet,
+        sym::BinaryHeap,
+    ];
+
+    if let QPath::TypeRelative(_, method) = path {
+        if method.ident.name == sym::new {
+            if let Some(impl_did) = cx.tcx.impl_of_method(def_id) {
+                if let Some(adt) = cx.tcx.type_of(impl_did).ty_adt_def() {
+                    return std_types_symbols
+                        .iter()
+                        .any(|&symbol| cx.tcx.is_diagnostic_item(symbol, adt.did));
+                }
+            }
+        }
+    }
+    false
+}
+
+/// Returns true if the expr is equal to `Default::default()` of it's type when evaluated.
+/// It doesn't cover all cases, for example indirect function calls (some of std
+/// functions are supported) but it is the best we have.
+pub fn is_default_equivalent(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
+    match &e.kind {
+        ExprKind::Lit(lit) => match lit.node {
+            LitKind::Bool(false) | LitKind::Int(0, _) => true,
+            LitKind::Str(s, _) => s.is_empty(),
+            _ => false,
+        },
+        ExprKind::Tup(items) | ExprKind::Array(items) => items.iter().all(|x| is_default_equivalent(cx, x)),
+        ExprKind::Repeat(x, _) => is_default_equivalent(cx, x),
+        ExprKind::Call(repl_func, _) => if_chain! {
+            if let ExprKind::Path(ref repl_func_qpath) = repl_func.kind;
+            if let Some(repl_def_id) = cx.qpath_res(repl_func_qpath, repl_func.hir_id).opt_def_id();
+            if is_diag_trait_item(cx, repl_def_id, sym::Default)
+                || is_default_equivalent_ctor(cx, repl_def_id, repl_func_qpath);
+            then {
+                true
+            }
+            else {
+                false
+            }
+        },
+        ExprKind::Path(qpath) => is_lang_ctor(cx, qpath, OptionNone),
+        ExprKind::AddrOf(rustc_hir::BorrowKind::Ref, _, expr) => matches!(expr.kind, ExprKind::Array([])),
+        _ => false,
+    }
+}
+
 /// Checks if the top level expression can be moved into a closure as is.
 /// Currently checks for:
 /// * Break/Continue outside the given loop HIR ids.
@@ -774,12 +833,11 @@ fn pat_capture_kind(cx: &LateContext<'_>, pat: &Pat<'_>) -> CaptureKind {
         ExprKind::Path(QPath::Resolved(None, Path { res: Res::Local(_), .. }))
     ));
 
-    let map = cx.tcx.hir();
     let mut child_id = e.hir_id;
     let mut capture = CaptureKind::Value;
     let mut capture_expr_ty = e;
 
-    for (parent_id, parent) in map.parent_iter(e.hir_id) {
+    for (parent_id, parent) in cx.tcx.hir().parent_iter(e.hir_id) {
         if let [Adjustment {
             kind: Adjust::Deref(_) | Adjust::Borrow(AutoBorrow::Ref(..)),
             target,
@@ -1165,8 +1223,7 @@ pub fn get_enclosing_block<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Optio
 
 /// Gets the loop or closure enclosing the given expression, if any.
 pub fn get_enclosing_loop_or_closure(tcx: TyCtxt<'tcx>, expr: &Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
-    let map = tcx.hir();
-    for (_, node) in map.parent_iter(expr.hir_id) {
+    for (_, node) in tcx.hir().parent_iter(expr.hir_id) {
         match node {
             Node::Expr(
                 e
@@ -1185,8 +1242,7 @@ pub fn get_enclosing_loop_or_closure(tcx: TyCtxt<'tcx>, expr: &Expr<'_>) -> Opti
 
 /// Gets the parent node if it's an impl block.
 pub fn get_parent_as_impl(tcx: TyCtxt<'_>, id: HirId) -> Option<&Impl<'_>> {
-    let map = tcx.hir();
-    match map.parent_iter(id).next() {
+    match tcx.hir().parent_iter(id).next() {
         Some((
             _,
             Node::Item(Item {
@@ -1200,8 +1256,7 @@ pub fn get_parent_as_impl(tcx: TyCtxt<'_>, id: HirId) -> Option<&Impl<'_>> {
 
 /// Checks if the given expression is the else clause of either an `if` or `if let` expression.
 pub fn is_else_clause(tcx: TyCtxt<'_>, expr: &Expr<'_>) -> bool {
-    let map = tcx.hir();
-    let mut iter = map.parent_iter(expr.hir_id);
+    let mut iter = tcx.hir().parent_iter(expr.hir_id);
     match iter.next() {
         Some((
             _,
@@ -1735,9 +1790,8 @@ fn is_body_identity_function(cx: &LateContext<'_>, func: &Body<'_>) -> bool {
 
 /// Gets the node where an expression is either used, or it's type is unified with another branch.
 pub fn get_expr_use_or_unification_node(tcx: TyCtxt<'tcx>, expr: &Expr<'_>) -> Option<Node<'tcx>> {
-    let map = tcx.hir();
     let mut child_id = expr.hir_id;
-    let mut iter = map.parent_iter(child_id);
+    let mut iter = tcx.hir().parent_iter(child_id);
     loop {
         match iter.next() {
             None => break None,