Auto merge of rust-lang#6506 - alex-700:add-path-buf-to-ptr-arg-lint, r=Manishearth

Lint "&PathBuf instead of &Path" in PTR_ARG

fixes rust-lang#6502

changelog: lint "`&PathBuf` instead of `&Path`" in `PTR_ARG`

Author: bors

clippy_dev/src/ra_setup.rs

@@ -3,7 +3,7 @@
 use std::fs;
 use std::fs::File;
 use std::io::prelude::*;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 // This module takes an absolute path to a rustc repo and alters the dependencies to point towards
 // the respective rustc subcrates instead of using extern crate xyz.
@@ -44,7 +44,7 @@ pub fn run(rustc_path: Option<&str>) {
 }
 
 fn inject_deps_into_manifest(
-    rustc_source_dir: &PathBuf,
+    rustc_source_dir: &Path,
     manifest_path: &str,
     cargo_toml: &str,
     lib_rs: &str,

clippy_lints/src/ptr.rs

@@ -182,20 +182,6 @@ fn check_fn(cx: &LateContext<'_>, decl: &FnDecl<'_>, fn_id: HirId, opt_body_id:
 
         if let ty::Ref(_, ty, Mutability::Not) = ty.kind() {
             if is_type_diagnostic_item(cx, ty, sym::vec_type) {
-                let mut ty_snippet = None;
-                if_chain! {
-                    if let TyKind::Path(QPath::Resolved(_, ref path)) = walk_ptrs_hir_ty(arg).kind;
-                    if let Some(&PathSegment{args: Some(ref parameters), ..}) = path.segments.last();
-                    then {
-                        let types: Vec<_> = parameters.args.iter().filter_map(|arg| match arg {
-                            GenericArg::Type(ty) => Some(ty),
-                            _ => None,
-                        }).collect();
-                        if types.len() == 1 {
-                            ty_snippet = snippet_opt(cx, types[0].span);
-                        }
-                    }
-                };
                 if let Some(spans) = get_spans(cx, opt_body_id, idx, &[("clone", ".to_owned()")]) {
                     span_lint_and_then(
                         cx,
@@ -204,7 +190,7 @@ fn check_fn(cx: &LateContext<'_>, decl: &FnDecl<'_>, fn_id: HirId, opt_body_id:
                         "writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used \
                          with non-Vec-based slices.",
                         |diag| {
-                            if let Some(ref snippet) = ty_snippet {
+                            if let Some(ref snippet) = get_only_generic_arg_snippet(cx, arg) {
                                 diag.span_suggestion(
                                     arg.span,
                                     "change this to",
@@ -247,6 +233,33 @@ fn check_fn(cx: &LateContext<'_>, decl: &FnDecl<'_>, fn_id: HirId, opt_body_id:
                         },
                     );
                 }
+            } else if match_type(cx, ty, &paths::PATH_BUF) {
+                if let Some(spans) = get_spans(cx, opt_body_id, idx, &[("clone", ".to_path_buf()"), ("as_path", "")]) {
+                    span_lint_and_then(
+                        cx,
+                        PTR_ARG,
+                        arg.span,
+                        "writing `&PathBuf` instead of `&Path` involves a new object where a slice will do.",
+                        |diag| {
+                            diag.span_suggestion(
+                                arg.span,
+                                "change this to",
+                                "&Path".into(),
+                                Applicability::Unspecified,
+                            );
+                            for (clonespan, suggestion) in spans {
+                                diag.span_suggestion_short(
+                                    clonespan,
+                                    &snippet_opt(cx, clonespan).map_or("change the call to".into(), |x| {
+                                        Cow::Owned(format!("change `{}` to", x))
+                                    }),
+                                    suggestion.into(),
+                                    Applicability::Unspecified,
+                                );
+                            }
+                        },
+                    );
+                }
             } else if match_type(cx, ty, &paths::COW) {
                 if_chain! {
                     if let TyKind::Rptr(_, MutTy { ref ty, ..} ) = arg.kind;
@@ -309,6 +322,23 @@ fn check_fn(cx: &LateContext<'_>, decl: &FnDecl<'_>, fn_id: HirId, opt_body_id:
     }
 }
 
+fn get_only_generic_arg_snippet(cx: &LateContext<'_>, arg: &Ty<'_>) -> Option<String> {
+    if_chain! {
+        if let TyKind::Path(QPath::Resolved(_, ref path)) = walk_ptrs_hir_ty(arg).kind;
+        if let Some(&PathSegment{args: Some(ref parameters), ..}) = path.segments.last();
+        let types: Vec<_> = parameters.args.iter().filter_map(|arg| match arg {
+            GenericArg::Type(ty) => Some(ty),
+            _ => None,
+        }).collect();
+        if types.len() == 1;
+        then {
+            snippet_opt(cx, types[0].span)
+        } else {
+            None
+        }
+    }
+}
+
 fn get_rptr_lm<'tcx>(ty: &'tcx Ty<'tcx>) -> Option<(&'tcx Lifetime, Mutability, Span)> {
     if let TyKind::Rptr(ref lt, ref m) = ty.kind {
         Some((lt, m.mutbl, ty.span))

tests/ui/ptr_arg.rs

@@ -2,6 +2,7 @@
 #![warn(clippy::ptr_arg)]
 
 use std::borrow::Cow;
+use std::path::PathBuf;
 
 fn do_vec(x: &Vec<i64>) {
     //Nothing here
@@ -21,6 +22,15 @@ fn do_str_mut(x: &mut String) {
     //Nothing here either
 }
 
+fn do_path(x: &PathBuf) {
+    //Nothing here either
+}
+
+fn do_path_mut(x: &mut PathBuf) {
+    // no error here
+    //Nothing here either
+}
+
 fn main() {}
 
 trait Foo {
@@ -55,6 +65,14 @@ fn str_cloned(x: &String) -> String {
     x.clone()
 }
 
+fn path_cloned(x: &PathBuf) -> PathBuf {
+    let a = x.clone();
+    let b = x.clone();
+    let c = b.clone();
+    let d = a.clone().clone().clone();
+    x.clone()
+}
+
 fn false_positive_capacity(x: &Vec<u8>, y: &String) {
     let a = x.capacity();
     let b = y.clone();
@@ -87,10 +105,12 @@ impl Foo2 for String {
 // Check that the allow attribute on parameters is honored
 mod issue_5644 {
     use std::borrow::Cow;
+    use std::path::PathBuf;
 
     fn allowed(
         #[allow(clippy::ptr_arg)] _v: &Vec<u32>,
         #[allow(clippy::ptr_arg)] _s: &String,
+        #[allow(clippy::ptr_arg)] _p: &PathBuf,
         #[allow(clippy::ptr_arg)] _c: &Cow<[i32]>,
     ) {
     }
@@ -100,6 +120,7 @@ mod issue_5644 {
         fn allowed(
             #[allow(clippy::ptr_arg)] _v: &Vec<u32>,
             #[allow(clippy::ptr_arg)] _s: &String,
+            #[allow(clippy::ptr_arg)] _p: &PathBuf,
             #[allow(clippy::ptr_arg)] _c: &Cow<[i32]>,
         ) {
         }
@@ -109,6 +130,7 @@ mod issue_5644 {
         fn allowed(
             #[allow(clippy::ptr_arg)] _v: &Vec<u32>,
             #[allow(clippy::ptr_arg)] _s: &String,
+            #[allow(clippy::ptr_arg)] _p: &PathBuf,
             #[allow(clippy::ptr_arg)] _c: &Cow<[i32]>,
         ) {
         }

tests/ui/ptr_arg.stderr

@@ -1,25 +1,31 @@
 error: writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used with non-Vec-based slices.
-  --> $DIR/ptr_arg.rs:6:14
+  --> $DIR/ptr_arg.rs:7:14
    |
 LL | fn do_vec(x: &Vec<i64>) {
    |              ^^^^^^^^^ help: change this to: `&[i64]`
    |
    = note: `-D clippy::ptr-arg` implied by `-D warnings`
 
 error: writing `&String` instead of `&str` involves a new object where a slice will do.
-  --> $DIR/ptr_arg.rs:15:14
+  --> $DIR/ptr_arg.rs:16:14
    |
 LL | fn do_str(x: &String) {
    |              ^^^^^^^ help: change this to: `&str`
 
+error: writing `&PathBuf` instead of `&Path` involves a new object where a slice will do.
+  --> $DIR/ptr_arg.rs:25:15
+   |
+LL | fn do_path(x: &PathBuf) {
+   |               ^^^^^^^^ help: change this to: `&Path`
+
 error: writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used with non-Vec-based slices.
-  --> $DIR/ptr_arg.rs:28:18
+  --> $DIR/ptr_arg.rs:38:18
    |
 LL |     fn do_vec(x: &Vec<i64>);
    |                  ^^^^^^^^^ help: change this to: `&[i64]`
 
 error: writing `&Vec<_>` instead of `&[_]` involves one more reference and cannot be used with non-Vec-based slices.
-  --> $DIR/ptr_arg.rs:41:14
+  --> $DIR/ptr_arg.rs:51:14
    |
 LL | fn cloned(x: &Vec<u8>) -> Vec<u8> {
    |              ^^^^^^^^
@@ -38,7 +44,7 @@ LL |     x.to_owned()
    |
 
 error: writing `&String` instead of `&str` involves a new object where a slice will do.
-  --> $DIR/ptr_arg.rs:50:18
+  --> $DIR/ptr_arg.rs:60:18
    |
 LL | fn str_cloned(x: &String) -> String {
    |                  ^^^^^^^
@@ -60,8 +66,31 @@ help: change `x.clone()` to
 LL |     x.to_string()
    |
 
+error: writing `&PathBuf` instead of `&Path` involves a new object where a slice will do.
+  --> $DIR/ptr_arg.rs:68:19
+   |
+LL | fn path_cloned(x: &PathBuf) -> PathBuf {
+   |                   ^^^^^^^^
+   |
+help: change this to
+   |
+LL | fn path_cloned(x: &Path) -> PathBuf {
+   |                   ^^^^^
+help: change `x.clone()` to
+   |
+LL |     let a = x.to_path_buf();
+   |             ^^^^^^^^^^^^^^^
+help: change `x.clone()` to
+   |
+LL |     let b = x.to_path_buf();
+   |             ^^^^^^^^^^^^^^^
+help: change `x.clone()` to
+   |
+LL |     x.to_path_buf()
+   |
+
 error: writing `&String` instead of `&str` involves a new object where a slice will do.
-  --> $DIR/ptr_arg.rs:58:44
+  --> $DIR/ptr_arg.rs:76:44
    |
 LL | fn false_positive_capacity(x: &Vec<u8>, y: &String) {
    |                                            ^^^^^^^
@@ -80,10 +109,10 @@ LL |     let c = y;
    |             ^
 
 error: using a reference to `Cow` is not recommended.
-  --> $DIR/ptr_arg.rs:72:25
+  --> $DIR/ptr_arg.rs:90:25
    |
 LL | fn test_cow_with_ref(c: &Cow<[i32]>) {}
    |                         ^^^^^^^^^^^ help: change this to: `&[i32]`
 
-error: aborting due to 7 previous errors
+error: aborting due to 9 previous errors