Auto merge of #5259 - flip1995:lang_items, r=phansch

Use lang items instead of get_trait_def_id where possible

changelog: none

clippy_lints/src/doc.rs

@@ -1,4 +1,4 @@
-use crate::utils::{get_trait_def_id, implements_trait, is_entrypoint_fn, match_type, paths, return_ty, span_lint};
+use crate::utils::{implements_trait, is_entrypoint_fn, match_type, paths, return_ty, span_lint};
 use if_chain::if_chain;
 use itertools::Itertools;
 use rustc::lint::in_external_macro;
@@ -227,7 +227,7 @@ fn lint_for_missing_headers<'a, 'tcx>(
         } else {
             if_chain! {
                 if let Some(body_id) = body_id;
-                if let Some(future) = get_trait_def_id(cx, &paths::FUTURE);
+                if let Some(future) = cx.tcx.lang_items().future_trait();
                 let def_id = cx.tcx.hir().body_owner_def_id(body_id);
                 let mir = cx.tcx.optimized_mir(def_id);
                 let ret_ty = mir.return_ty();

clippy_lints/src/inherent_to_string.rs

@@ -120,8 +120,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for InherentToString {
 }
 
 fn show_lint(cx: &LateContext<'_, '_>, item: &ImplItem<'_>) {
-    let display_trait_id =
-        get_trait_def_id(cx, &["core", "fmt", "Display"]).expect("Failed to get trait ID of `Display`!");
+    let display_trait_id = get_trait_def_id(cx, &paths::DISPLAY_TRAIT).expect("Failed to get trait ID of `Display`!");
 
     // Get the real type of 'self'
     let fn_def_id = cx.tcx.hir().local_def_id(item.hir_id);

clippy_lints/src/neg_cmp_op_on_partial_ord.rs

@@ -67,7 +67,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NoNegCompOpForPartialOrd {
                 };
 
                 let implements_partial_ord = {
-                    if let Some(id) = utils::get_trait_def_id(cx, &paths::PARTIAL_ORD) {
+                    if let Some(id) = cx.tcx.lang_items().partial_ord_trait() {
                         utils::implements_trait(cx, ty, id, &[])
                     } else {
                         return;

clippy_lints/src/utils/paths.rs

@@ -24,6 +24,7 @@ pub const DEFAULT_TRAIT_METHOD: [&str; 4] = ["core", "default", "Default", "defa
 pub const DEREF_MUT_TRAIT_METHOD: [&str; 5] = ["core", "ops", "deref", "DerefMut", "deref_mut"];
 pub const DEREF_TRAIT_METHOD: [&str; 5] = ["core", "ops", "deref", "Deref", "deref"];
 pub const DISPLAY_FMT_METHOD: [&str; 4] = ["core", "fmt", "Display", "fmt"];
+pub const DISPLAY_TRAIT: [&str; 3] = ["core", "fmt", "Display"];
 pub const DOUBLE_ENDED_ITERATOR: [&str; 4] = ["core", "iter", "traits", "DoubleEndedIterator"];
 pub const DROP: [&str; 3] = ["core", "mem", "drop"];
 pub const DROP_TRAIT: [&str; 4] = ["core", "ops", "drop", "Drop"];
@@ -36,7 +37,6 @@ pub const FMT_ARGUMENTS_NEW_V1_FORMATTED: [&str; 4] = ["core", "fmt", "Arguments
 pub const FMT_ARGUMENTV1_NEW: [&str; 4] = ["core", "fmt", "ArgumentV1", "new"];
 pub const FROM_FROM: [&str; 4] = ["core", "convert", "From", "from"];
 pub const FROM_TRAIT: [&str; 3] = ["core", "convert", "From"];
-pub const FUTURE: [&str; 3] = ["std", "future", "Future"];
 pub const HASH: [&str; 2] = ["hash", "Hash"];
 pub const HASHMAP: [&str; 5] = ["std", "collections", "hash", "map", "HashMap"];
 pub const HASHMAP_ENTRY: [&str; 5] = ["std", "collections", "hash", "map", "Entry"];
@@ -69,7 +69,6 @@ pub const ORD: [&str; 3] = ["core", "cmp", "Ord"];
 pub const OS_STRING: [&str; 4] = ["std", "ffi", "os_str", "OsString"];
 pub const OS_STRING_AS_OS_STR: [&str; 5] = ["std", "ffi", "os_str", "OsString", "as_os_str"];
 pub const OS_STR_TO_OS_STRING: [&str; 5] = ["std", "ffi", "os_str", "OsStr", "to_os_string"];
-pub const PARTIAL_ORD: [&str; 3] = ["core", "cmp", "PartialOrd"];
 pub const PATH: [&str; 3] = ["std", "path", "Path"];
 pub const PATH_BUF: [&str; 3] = ["std", "path", "PathBuf"];
 pub const PATH_BUF_AS_PATH: [&str; 4] = ["std", "path", "PathBuf", "as_path"];