migrate paths to newly-added diagnostic items

This gets rid of the following paths:
  * OS_STRING
  * TO_OWNED
  * TO_STRING

Also removes some usages of:
  * PATH_BUF

And the now completely unused `clippy_lints::types::is_ty_param_path`

clippy_lints/src/misc.rs

@@ -12,12 +12,13 @@ use rustc_middle::ty::{self, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::source_map::{ExpnKind, Span};
+use rustc_span::symbol::sym;
 
 use crate::consts::{constant, Constant};
 use crate::utils::sugg::Sugg;
 use crate::utils::{
-    get_item_name, get_parent_expr, higher, implements_trait, in_constant, is_integer_const, iter_input_pats,
-    last_path_segment, match_qpath, match_trait_method, paths, snippet, snippet_opt, span_lint, span_lint_and_sugg,
+    get_item_name, get_parent_expr, higher, implements_trait, in_constant, is_diagnostic_assoc_item, is_integer_const,
+    iter_input_pats, last_path_segment, match_qpath, snippet, snippet_opt, span_lint, span_lint_and_sugg,
     span_lint_and_then, span_lint_hir_and_then, unsext, SpanlessEq,
 };
 
@@ -554,11 +555,16 @@ fn check_to_owned(cx: &LateContext<'_>, expr: &Expr<'_>, other: &Expr<'_>, left:
 
     let (arg_ty, snip) = match expr.kind {
         ExprKind::MethodCall(.., ref args, _) if args.len() == 1 => {
-            if match_trait_method(cx, expr, &paths::TO_STRING) || match_trait_method(cx, expr, &paths::TO_OWNED) {
-                (cx.typeck_results().expr_ty(&args[0]), snippet(cx, args[0].span, ".."))
-            } else {
-                return;
-            }
+            if_chain!(
+                if let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
+                if is_diagnostic_assoc_item(cx, expr_def_id, sym::ToString)
+                    || is_diagnostic_assoc_item(cx, expr_def_id, sym::ToOwned);
+                then {
+                    (cx.typeck_results().expr_ty(&args[0]), snippet(cx, args[0].span, ".."))
+                } else {
+                    return;
+                }
+            )
         },
         ExprKind::Call(ref path, ref v) if v.len() == 1 => {
             if let ExprKind::Path(ref path) = path.kind {

clippy_lints/src/path_buf_push_overwrite.rs

@@ -1,10 +1,11 @@
-use crate::utils::{match_type, paths, span_lint_and_sugg};
+use crate::utils::{is_type_diagnostic_item, span_lint_and_sugg};
 use if_chain::if_chain;
 use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::symbol::sym;
 use std::path::{Component, Path};
 
 declare_clippy_lint! {
@@ -46,7 +47,7 @@ impl<'tcx> LateLintPass<'tcx> for PathBufPushOverwrite {
             if let ExprKind::MethodCall(ref path, _, ref args, _) = expr.kind;
             if path.ident.name == sym!(push);
             if args.len() == 2;
-            if match_type(cx, cx.typeck_results().expr_ty(&args[0]).peel_refs(), &paths::PATH_BUF);
+            if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(&args[0]).peel_refs(), sym::PathBuf);
             if let Some(get_index_arg) = args.get(1);
             if let ExprKind::Lit(ref lit) = get_index_arg.kind;
             if let LitKind::Str(ref path_lit, _) = lit.node;

clippy_lints/src/ptr.rs

@@ -233,7 +233,7 @@ fn check_fn(cx: &LateContext<'_>, decl: &FnDecl<'_>, fn_id: HirId, opt_body_id:
                         },
                     );
                 }
-            } else if match_type(cx, ty, &paths::PATH_BUF) {
+            } else if is_type_diagnostic_item(cx, ty, sym::PathBuf) {
                 if let Some(spans) = get_spans(cx, opt_body_id, idx, &[("clone", ".to_path_buf()"), ("as_path", "")]) {
                     span_lint_and_then(
                         cx,

clippy_lints/src/redundant_clone.rs

@@ -1,6 +1,6 @@
 use crate::utils::{
-    fn_has_unsatisfiable_preds, has_drop, is_copy, is_type_diagnostic_item, match_def_path, match_type, paths,
-    snippet_opt, span_lint_hir, span_lint_hir_and_then, walk_ptrs_ty_depth,
+    fn_has_unsatisfiable_preds, has_drop, is_copy, is_type_diagnostic_item, match_def_path, paths, snippet_opt,
+    span_lint_hir, span_lint_hir_and_then, walk_ptrs_ty_depth,
 };
 use if_chain::if_chain;
 use rustc_data_structures::{fx::FxHashMap, transitive_relation::TransitiveRelation};
@@ -166,8 +166,8 @@ impl<'tcx> LateLintPass<'tcx> for RedundantClone {
                         is_call_with_ref_arg(cx, mir, &pred_terminator.kind);
                     if res == cloned;
                     if cx.tcx.is_diagnostic_item(sym::deref_method, pred_fn_def_id);
-                    if match_type(cx, pred_arg_ty, &paths::PATH_BUF)
-                        || match_type(cx, pred_arg_ty, &paths::OS_STRING);
+                    if is_type_diagnostic_item(cx, pred_arg_ty, sym::PathBuf)
+                        || is_type_diagnostic_item(cx, pred_arg_ty, sym::OsString);
                     then {
                         (pred_arg, res)
                     } else {

clippy_lints/src/to_string_in_display.rs

@@ -1,8 +1,9 @@
-use crate::utils::{match_def_path, match_trait_method, path_to_local_id, paths, span_lint};
+use crate::utils::{is_diagnostic_assoc_item, match_def_path, path_to_local_id, paths, span_lint};
 use if_chain::if_chain;
 use rustc_hir::{Expr, ExprKind, HirId, Impl, ImplItem, ImplItemKind, Item, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::symbol::sym;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for uses of `to_string()` in `Display` traits.
@@ -92,7 +93,8 @@ impl LateLintPass<'_> for ToStringInDisplay {
             if let Some(self_hir_id) = self.self_hir_id;
             if let ExprKind::MethodCall(ref path, _, args, _) = expr.kind;
             if path.ident.name == sym!(to_string);
-            if match_trait_method(cx, expr, &paths::TO_STRING);
+            if let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
+            if is_diagnostic_assoc_item(cx, expr_def_id, sym::ToString);
             if path_to_local_id(&args[0], self_hir_id);
             then {
                 span_lint(

clippy_lints/src/types.rs

@@ -313,25 +313,12 @@ fn is_ty_param_diagnostic_item(cx: &LateContext<'_>, qpath: &QPath<'tcx>, item:
     }
 }
 
-/// Checks if the first type parameter is a given item.
-fn is_ty_param_path(cx: &LateContext<'_>, qpath: &QPath<'tcx>, path: &[&str]) -> Option<&'tcx hir::Ty<'tcx>> {
-    let ty = get_qpath_generic_tys(qpath).next()?;
-
-    if let TyKind::Path(qpath) = &ty.kind {
-        cx.qpath_res(qpath, ty.hir_id)
-            .opt_def_id()
-            .and_then(|id| match_def_path(cx, id, path).then(|| ty))
-    } else {
-        None
-    }
-}
-
 fn match_buffer_type(cx: &LateContext<'_>, qpath: &QPath<'_>) -> Option<&'static str> {
     if is_ty_param_diagnostic_item(cx, qpath, sym::string_type).is_some() {
         Some("str")
-    } else if is_ty_param_path(cx, qpath, &paths::OS_STRING).is_some() {
+    } else if is_ty_param_diagnostic_item(cx, qpath, sym::OsString).is_some() {
         Some("std::ffi::OsStr")
-    } else if is_ty_param_path(cx, qpath, &paths::PATH_BUF).is_some() {
+    } else if is_ty_param_diagnostic_item(cx, qpath, sym::PathBuf).is_some() {
         Some("std::path::Path")
     } else {
         None

clippy_utils/src/paths.rs

@@ -84,7 +84,6 @@ pub const OPTION: [&str; 3] = ["core", "option", "Option"];
 pub const OPTION_NONE: [&str; 4] = ["core", "option", "Option", "None"];
 pub const OPTION_SOME: [&str; 4] = ["core", "option", "Option", "Some"];
 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(super) const PANICKING_PANIC: [&str; 3] = ["core", "panicking", "panic"];
@@ -155,9 +154,7 @@ pub const SYMBOL_TO_IDENT_STRING: [&str; 4] = ["rustc_span", "symbol", "Symbol",
 pub const SYM_MODULE: [&str; 3] = ["rustc_span", "symbol", "sym"];
 #[cfg(feature = "internal-lints")]
 pub const SYNTAX_CONTEXT: [&str; 3] = ["rustc_span", "hygiene", "SyntaxContext"];
-pub const TO_OWNED: [&str; 3] = ["alloc", "borrow", "ToOwned"];
 pub const TO_OWNED_METHOD: [&str; 4] = ["alloc", "borrow", "ToOwned", "to_owned"];
-pub const TO_STRING: [&str; 3] = ["alloc", "string", "ToString"];
 pub const TO_STRING_METHOD: [&str; 4] = ["alloc", "string", "ToString", "to_string"];
 pub const TRANSMUTE: [&str; 4] = ["core", "intrinsics", "", "transmute"];
 pub const TRY_FROM: [&str; 4] = ["core", "convert", "TryFrom", "try_from"];