implementation using new diagnostic items

Signed-off-by: Max Baumann <max@bmn.dev>

Author: FoseFx

clippy_lints/src/strings.rs

@@ -1,14 +1,15 @@
 use clippy_utils::diagnostics::{span_lint, span_lint_and_help, span_lint_and_sugg};
 use clippy_utils::source::{snippet, snippet_with_applicability};
-use clippy_utils::ty::{get_associated_type, implements_trait, is_type_diagnostic_item};
+use clippy_utils::ty::is_type_diagnostic_item;
 use clippy_utils::{get_parent_expr, is_lint_allowed, match_function_call, method_calls, paths};
 use clippy_utils::{peel_blocks, SpanlessEq};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
+use rustc_hir::def_id::DefId;
 use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, LangItem, QPath};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::{self, Ty};
+use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::Spanned;
 use rustc_span::sym;
@@ -476,13 +477,16 @@ declare_lint_pass!(TrimSplitWhitespace => [TRIM_SPLIT_WHITESPACE]);
 
 impl<'tcx> LateLintPass<'tcx> for TrimSplitWhitespace {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
+        let tyckres = cx.typeck_results();
         if_chain! {
-            if let ExprKind::MethodCall(path, [recv], split_ws_span) = expr.kind;
+            if let ExprKind::MethodCall(path, [split_recv], split_ws_span) = expr.kind;
             if path.ident.name == sym!(split_whitespace);
-            if let ExprKind::MethodCall(path, [recv], trim_span) = recv.kind;
+            if let Some(split_ws_def_id) = tyckres.type_dependent_def_id(expr.hir_id);
+            if cx.tcx.is_diagnostic_item(sym::str_split_whitespace, split_ws_def_id);
+            if let ExprKind::MethodCall(path, [_trim_recv], trim_span) = split_recv.kind;
             if let trim_fn_name @ ("trim" | "trim_start" | "trim_end") = path.ident.name.as_str();
-            let recv_ty = cx.typeck_results().expr_ty(recv).peel_refs();
-            if recv_ty.is_str() || implements_deref_str(cx, recv_ty);
+            if let Some(trim_def_id) = tyckres.type_dependent_def_id(split_recv.hir_id);
+            if is_one_of_trim_diagnostic_items(cx, trim_def_id);
             then {
                 span_lint_and_sugg(
                     cx,
@@ -498,17 +502,8 @@ impl<'tcx> LateLintPass<'tcx> for TrimSplitWhitespace {
     }
 }
 
-/// does ty implement Deref<Target=str>?
-fn implements_deref_str<'t>(cx: &LateContext<'t>, ty: Ty<'t>) -> bool {
-    if_chain! {
-        if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
-        if implements_trait(cx, ty, deref_trait_id, &[]);
-        if let Some(target) = get_associated_type(cx, ty, deref_trait_id, "Target");
-        then {
-            target.is_str()
-        }
-        else {
-            false
-        }
-    }
+fn is_one_of_trim_diagnostic_items(cx: &LateContext<'_>, trim_def_id: DefId) -> bool {
+    cx.tcx.is_diagnostic_item(sym::str_trim, trim_def_id)
+        || cx.tcx.is_diagnostic_item(sym::str_trim_start, trim_def_id)
+        || cx.tcx.is_diagnostic_item(sym::str_trim_end, trim_def_id)
 }