Auto merge of #10063 - chansuke:issue-9702, r=Alexendoo

add [`permissions_set_readonly_false`] #9702

Add slight modification on [this PR](rust-lang/rust-clippy#9744).

---

changelog: New lint [`permissions_set_readonly_false`]
[#10063](rust-lang/rust-clippy#10063)
<!-- changelog_checked -->

CHANGELOG.md

@@ -4461,6 +4461,7 @@ Released 2018-09-13
 [`partialeq_to_none`]: https://rust-lang.github.io/rust-clippy/master/index.html#partialeq_to_none
 [`path_buf_push_overwrite`]: https://rust-lang.github.io/rust-clippy/master/index.html#path_buf_push_overwrite
 [`pattern_type_mismatch`]: https://rust-lang.github.io/rust-clippy/master/index.html#pattern_type_mismatch
+[`permissions_set_readonly_false`]: https://rust-lang.github.io/rust-clippy/master/index.html#permissions_set_readonly_false
 [`positional_named_format_parameters`]: https://rust-lang.github.io/rust-clippy/master/index.html#positional_named_format_parameters
 [`possible_missing_comma`]: https://rust-lang.github.io/rust-clippy/master/index.html#possible_missing_comma
 [`precedence`]: https://rust-lang.github.io/rust-clippy/master/index.html#precedence

clippy_lints/src/declared_lints.rs

@@ -495,6 +495,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::pass_by_ref_or_value::LARGE_TYPES_PASSED_BY_VALUE_INFO,
     crate::pass_by_ref_or_value::TRIVIALLY_COPY_PASS_BY_REF_INFO,
     crate::pattern_type_mismatch::PATTERN_TYPE_MISMATCH_INFO,
+    crate::permissions_set_readonly_false::PERMISSIONS_SET_READONLY_FALSE_INFO,
     crate::precedence::PRECEDENCE_INFO,
     crate::ptr::CMP_NULL_INFO,
     crate::ptr::INVALID_NULL_PTR_USAGE_INFO,

clippy_lints/src/lib.rs

@@ -235,6 +235,7 @@ mod partialeq_ne_impl;
 mod partialeq_to_none;
 mod pass_by_ref_or_value;
 mod pattern_type_mismatch;
+mod permissions_set_readonly_false;
 mod precedence;
 mod ptr;
 mod ptr_offset_with_cast;
@@ -904,6 +905,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(move |_| Box::new(manual_is_ascii_check::ManualIsAsciiCheck::new(msrv())));
     store.register_late_pass(|_| Box::new(semicolon_block::SemicolonBlock));
     store.register_late_pass(|_| Box::new(fn_null_check::FnNullCheck));
+    store.register_late_pass(|_| Box::new(permissions_set_readonly_false::PermissionsSetReadonlyFalse));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/permissions_set_readonly_false.rs

@@ -0,0 +1,52 @@
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::paths;
+use clippy_utils::ty::match_type;
+use rustc_ast::ast::LitKind;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for calls to `std::fs::Permissions.set_readonly` with argument `false`.
+    ///
+    /// ### Why is this bad?
+    /// On Unix platforms this results in the file being world writable,
+    /// equivalent to `chmod a+w <file>`.
+    /// ### Example
+    /// ```rust
+    /// use std::fs::File;
+    /// let f = File::create("foo.txt").unwrap();
+    /// let metadata = f.metadata().unwrap();
+    /// let mut permissions = metadata.permissions();
+    /// permissions.set_readonly(false);
+    /// ```
+    #[clippy::version = "1.66.0"]
+    pub PERMISSIONS_SET_READONLY_FALSE,
+    suspicious,
+    "Checks for calls to `std::fs::Permissions.set_readonly` with argument `false`"
+}
+declare_lint_pass!(PermissionsSetReadonlyFalse => [PERMISSIONS_SET_READONLY_FALSE]);
+
+impl<'tcx> LateLintPass<'tcx> for PermissionsSetReadonlyFalse {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        if let ExprKind::MethodCall(path, receiver, [arg], _) = &expr.kind
+            && match_type(cx, cx.typeck_results().expr_ty(receiver), &paths::PERMISSIONS)
+            && path.ident.name == sym!(set_readonly)
+            && let ExprKind::Lit(lit) = &arg.kind
+            && LitKind::Bool(false) == lit.node
+        {
+            span_lint_and_then(
+                cx,
+                PERMISSIONS_SET_READONLY_FALSE,
+                expr.span,
+                "call to `set_readonly` with argument `false`",
+                |diag| {
+                    diag.note("on Unix platforms this results in the file being world writable");
+                    diag.help("you can set the desired permissions using `PermissionsExt`. For more information, see\n\
+                        https://doc.rust-lang.org/std/os/unix/fs/trait.PermissionsExt.html");
+                }
+            );
+        }
+    }
+}

tests/ui/permissions_set_readonly_false.rs

@@ -0,0 +1,29 @@
+#![allow(unused)]
+#![warn(clippy::permissions_set_readonly_false)]
+
+use std::fs::File;
+
+struct A;
+
+impl A {
+    pub fn set_readonly(&mut self, b: bool) {}
+}
+
+fn set_readonly(b: bool) {}
+
+fn main() {
+    let f = File::create("foo.txt").unwrap();
+    let metadata = f.metadata().unwrap();
+    let mut permissions = metadata.permissions();
+    // lint here
+    permissions.set_readonly(false);
+    // no lint
+    permissions.set_readonly(true);
+
+    let mut a = A;
+    // no lint here - a is not of type std::fs::Permissions
+    a.set_readonly(false);
+
+    // no lint here - plain function
+    set_readonly(false);
+}

tests/ui/permissions_set_readonly_false.stderr

@@ -0,0 +1,13 @@
+error: call to `set_readonly` with argument `false`
+  --> $DIR/permissions_set_readonly_false.rs:19:5
+   |
+LL |     permissions.set_readonly(false);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: on Unix platforms this results in the file being world writable
+   = help: you can set the desired permissions using `PermissionsExt`. For more information, see
+           https://doc.rust-lang.org/std/os/unix/fs/trait.PermissionsExt.html
+   = note: `-D clippy::permissions-set-readonly-false` implied by `-D warnings`
+
+error: aborting due to previous error
+