mem_replace_with_default: use diagnostic items intead of paths

Author: mgacek8

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(

clippy_utils/src/lib.rs

@@ -279,7 +279,7 @@ pub fn match_trait_method(cx: &LateContext<'_>, expr: &Expr<'_>, path: &[&str])
     trt_id.map_or(false, |trt_id| match_def_path(cx, trt_id, path))
 }
 
-/// Checks if the method call given in `expr` belongs to a trait or other container with a given
+/// Checks if the method call given in `def_id` belongs to a trait or other container with a given
 /// diagnostic item
 pub fn is_diagnostic_assoc_item(cx: &LateContext<'_>, def_id: DefId, diag_item: Symbol) -> bool {
     cx.tcx

clippy_utils/src/paths.rs

@@ -11,13 +11,10 @@ pub const ASREF_TRAIT: [&str; 3] = ["core", "convert", "AsRef"];
 pub(super) const BEGIN_PANIC: [&str; 3] = ["std", "panicking", "begin_panic"];
 pub(super) const BEGIN_PANIC_FMT: [&str; 3] = ["std", "panicking", "begin_panic_fmt"];
 pub const BINARY_HEAP: [&str; 4] = ["alloc", "collections", "binary_heap", "BinaryHeap"];
-pub const BINARY_HEAP_NEW: [&str; 5] = ["alloc", "collections", "binary_heap", "BinaryHeap", "new"];
 pub const BORROW_TRAIT: [&str; 3] = ["core", "borrow", "Borrow"];
 pub const BTREEMAP: [&str; 5] = ["alloc", "collections", "btree", "map", "BTreeMap"];
-pub const BTREEMAP_NEW: [&str; 6] = ["alloc", "collections", "btree", "map", "BTreeMap", "new"];
 pub const BTREEMAP_ENTRY: [&str; 6] = ["alloc", "collections", "btree", "map", "entry", "Entry"];
 pub const BTREESET: [&str; 5] = ["alloc", "collections", "btree", "set", "BTreeSet"];
-pub const BTREESET_NEW: [&str; 6] = ["alloc", "collections", "btree", "set", "BTreeSet", "new"];
 pub const CLONE_TRAIT_METHOD: [&str; 4] = ["core", "clone", "Clone", "clone"];
 pub const CMP_MAX: [&str; 3] = ["core", "cmp", "max"];
 pub const CMP_MIN: [&str; 3] = ["core", "cmp", "min"];
@@ -49,10 +46,8 @@ pub const FROM_ITERATOR: [&str; 5] = ["core", "iter", "traits", "collect", "From
 pub const FUTURE_FROM_GENERATOR: [&str; 3] = ["core", "future", "from_generator"];
 pub const HASH: [&str; 3] = ["core", "hash", "Hash"];
 pub const HASHMAP: [&str; 5] = ["std", "collections", "hash", "map", "HashMap"];
-pub const HASHMAP_NEW: [&str; 6] = ["std", "collections", "hash", "map", "HashMap", "new"];
 pub const HASHMAP_ENTRY: [&str; 5] = ["std", "collections", "hash", "map", "Entry"];
 pub const HASHSET: [&str; 5] = ["std", "collections", "hash", "set", "HashSet"];
-pub const HASHSET_NEW: [&str; 6] = ["std", "collections", "hash", "set", "HashSet", "new"];
 #[cfg(feature = "internal-lints")]
 pub const IDENT: [&str; 3] = ["rustc_span", "symbol", "Ident"];
 #[cfg(feature = "internal-lints")]
@@ -72,7 +67,6 @@ pub const KW_MODULE: [&str; 3] = ["rustc_span", "symbol", "kw"];
 #[cfg(feature = "internal-lints")]
 pub const LATE_CONTEXT: [&str; 2] = ["rustc_lint", "LateContext"];
 pub const LINKED_LIST: [&str; 4] = ["alloc", "collections", "linked_list", "LinkedList"];
-pub const LINKED_LIST_NEW: [&str; 5] = ["alloc", "collections", "linked_list", "LinkedList", "new"];
 #[cfg(feature = "internal-lints")]
 pub const LINT: [&str; 2] = ["rustc_lint_defs", "Lint"];
 pub const MEM_DISCRIMINANT: [&str; 3] = ["core", "mem", "discriminant"];
@@ -140,7 +134,6 @@ pub const STD_CONVERT_IDENTITY: [&str; 3] = ["std", "convert", "identity"];
 pub const STD_FS_CREATE_DIR: [&str; 3] = ["std", "fs", "create_dir"];
 pub const STD_MEM_TRANSMUTE: [&str; 3] = ["std", "mem", "transmute"];
 pub const STD_PTR_NULL: [&str; 3] = ["std", "ptr", "null"];
-pub const STRING_NEW: [&str; 4] = ["alloc", "string", "String", "new"];
 pub const STRING_AS_MUT_STR: [&str; 4] = ["alloc", "string", "String", "as_mut_str"];
 pub const STRING_AS_STR: [&str; 4] = ["alloc", "string", "String", "as_str"];
 pub const STR_ENDS_WITH: [&str; 4] = ["core", "str", "<impl str>", "ends_with"];
@@ -168,7 +161,6 @@ pub const VEC: [&str; 3] = ["alloc", "vec", "Vec"];
 pub const VEC_AS_MUT_SLICE: [&str; 4] = ["alloc", "vec", "Vec", "as_mut_slice"];
 pub const VEC_AS_SLICE: [&str; 4] = ["alloc", "vec", "Vec", "as_slice"];
 pub const VEC_DEQUE: [&str; 4] = ["alloc", "collections", "vec_deque", "VecDeque"];
-pub const VEC_DEQUE_NEW: [&str; 5] = ["alloc", "collections", "vec_deque", "VecDeque", "new"];
 pub const VEC_FROM_ELEM: [&str; 3] = ["alloc", "vec", "from_elem"];
 pub const VEC_NEW: [&str; 4] = ["alloc", "vec", "Vec", "new"];
 pub const VEC_RESIZE: [&str; 4] = ["alloc", "vec", "Vec", "resize"];