mem_replace_with_default: use diagnostic items intead of paths

clippy_lints/src/mem_replace.rs

@@ -4,6 +4,7 @@ use crate::utils::{
 };
 use if_chain::if_chain;
 use rustc_errors::Applicability;
+use rustc_hir::def_id::DefId;
 use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability, QPath};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
@@ -12,6 +13,8 @@ use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::source_map::Span;
 use rustc_span::symbol::sym;
 
+use clippy_utils::is_diagnostic_assoc_item;
+
 declare_clippy_lint! {
     /// **What it does:** Checks for `mem::replace()` on an `Option` with
     /// `None`.
@@ -194,27 +197,43 @@ fn check_replace_with_uninit(cx: &LateContext<'_>, src: &Expr<'_>, dest: &Expr<'
     }
 }
 
+/// 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 std_types_symbols
+        .iter()
+        .any(|symbol| is_diagnostic_assoc_item(cx, def_id, *symbol))
+    {
+        if let QPath::TypeRelative(_, ref method) = path {
+            if method.ident.name == sym::new {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
 fn check_replace_with_default(cx: &LateContext<'_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
     if let ExprKind::Call(ref repl_func, _) = src.kind {
         if_chain! {
             if !in_external_macro(cx.tcx.sess, expr_span);
             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();
-
-            let defaults = &[
-                paths::DEFAULT_TRAIT_METHOD.as_ref(),
-                paths::STRING_NEW.as_ref(),
-                paths::VEC_NEW.as_ref(),
-                paths::VEC_DEQUE_NEW.as_ref(),
-                paths::LINKED_LIST_NEW.as_ref(),
-                paths::HASHMAP_NEW.as_ref(),
-                paths::BTREEMAP_NEW.as_ref(),
-                paths::HASHSET_NEW.as_ref(),
-                paths::BTREESET_NEW.as_ref(),
-                paths::BINARY_HEAP_NEW.as_ref(),
-            ];
-
-            if defaults.iter().any(|x| match_def_path(cx, repl_def_id, &x));
+            if is_diagnostic_assoc_item(cx, repl_def_id, sym::Default)
+                || is_default_equivalent_ctor(cx, repl_def_id, repl_func_qpath);
 
             then {
                 span_lint_and_then(