diff --git a/CHANGELOG.md b/CHANGELOG.md
index 768751b2f08..9ad6514ee10 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -744,6 +744,7 @@ All notable changes to this project will be documented in this file.
[`match_same_arms`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#match_same_arms
[`match_wild_err_arm`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#match_wild_err_arm
[`maybe_infinite_iter`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#maybe_infinite_iter
+[`mem_discriminant_non_enum`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#mem_discriminant_non_enum
[`mem_forget`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#mem_forget
[`mem_replace_option_with_none`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#mem_replace_option_with_none
[`min_max`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#min_max
diff --git a/README.md b/README.md
index 94fb8c6c02f..a13d8ecef66 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ We are currently in the process of discussing Clippy 1.0 via the RFC process in
A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
-[There are 281 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
+[There are 282 lints included in this crate!](https://rust-lang-nursery.github.io/rust-clippy/master/index.html)
We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 8b2070561d2..7a91890633a 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -144,6 +144,7 @@ pub mod loops;
pub mod map_clone;
pub mod map_unit_fn;
pub mod matches;
+pub mod mem_discriminant;
pub mod mem_forget;
pub mod mem_replace;
pub mod methods;
@@ -398,6 +399,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
reg.register_early_lint_pass(box doc::Doc::new(conf.doc_valid_idents.clone()));
reg.register_late_lint_pass(box neg_multiply::NegMultiply);
reg.register_early_lint_pass(box unsafe_removed_from_name::UnsafeNameRemoval);
+ reg.register_late_lint_pass(box mem_discriminant::MemDiscriminant);
reg.register_late_lint_pass(box mem_forget::MemForget);
reg.register_late_lint_pass(box mem_replace::MemReplace);
reg.register_late_lint_pass(box arithmetic::Arithmetic::default());
@@ -612,6 +614,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
matches::MATCH_REF_PATS,
matches::MATCH_WILD_ERR_ARM,
matches::SINGLE_MATCH,
+ mem_discriminant::MEM_DISCRIMINANT_NON_ENUM,
mem_replace::MEM_REPLACE_OPTION_WITH_NONE,
methods::CHARS_LAST_CMP,
methods::CHARS_NEXT_CMP,
@@ -924,6 +927,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
loops::NEVER_LOOP,
loops::REVERSE_RANGE_LOOP,
loops::WHILE_IMMUTABLE_CONDITION,
+ mem_discriminant::MEM_DISCRIMINANT_NON_ENUM,
methods::CLONE_DOUBLE_REF,
methods::TEMPORARY_CSTRING_AS_PTR,
minmax::MIN_MAX,
diff --git a/clippy_lints/src/mem_discriminant.rs b/clippy_lints/src/mem_discriminant.rs
new file mode 100644
index 00000000000..356162fd6f4
--- /dev/null
+++ b/clippy_lints/src/mem_discriminant.rs
@@ -0,0 +1,93 @@
+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+use crate::rustc::hir::{Expr, ExprKind};
+use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use crate::rustc::{declare_tool_lint, lint_array};
+use crate::utils::{match_def_path, opt_def_id, paths, snippet, span_lint_and_then, walk_ptrs_ty_depth};
+use if_chain::if_chain;
+
+use std::iter;
+
+/// **What it does:** Checks for calls of `mem::discriminant()` on a non-enum type.
+///
+/// **Why is this bad?** The value of `mem::discriminant()` on non-enum types
+/// is unspecified.
+///
+/// **Known problems:** None.
+///
+/// **Example:**
+/// ```rust
+/// mem::discriminant(&"hello");
+/// mem::discriminant(&&Some(2));
+/// ```
+declare_clippy_lint! {
+ pub MEM_DISCRIMINANT_NON_ENUM,
+ correctness,
+ "calling mem::descriminant on non-enum type"
+}
+
+pub struct MemDiscriminant;
+
+impl LintPass for MemDiscriminant {
+ fn get_lints(&self) -> LintArray {
+ lint_array![MEM_DISCRIMINANT_NON_ENUM]
+ }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemDiscriminant {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
+ if_chain! {
+ if let ExprKind::Call(ref func, ref func_args) = expr.node;
+ // is `mem::discriminant`
+ if let ExprKind::Path(ref func_qpath) = func.node;
+ if let Some(def_id) = opt_def_id(cx.tables.qpath_def(func_qpath, func.hir_id));
+ if match_def_path(cx.tcx, def_id, &paths::MEM_DISCRIMINANT);
+ // type is non-enum
+ let ty_param = cx.tables.node_substs(func.hir_id).type_at(0);
+ if !ty_param.is_enum();
+
+ then {
+ span_lint_and_then(
+ cx,
+ MEM_DISCRIMINANT_NON_ENUM,
+ expr.span,
+ &format!("calling `mem::discriminant` on non-enum type `{}`", ty_param),
+ |db| {
+ // if this is a reference to an enum, suggest dereferencing
+ let (base_ty, ptr_depth) = walk_ptrs_ty_depth(ty_param);
+ if ptr_depth >= 1 && base_ty.is_enum() {
+ let param = &func_args[0];
+
+ // cancel out '&'s first
+ let mut derefs_needed = ptr_depth;
+ let mut cur_expr = param;
+ while derefs_needed > 0 {
+ if let ExprKind::AddrOf(_, ref inner_expr) = cur_expr.node {
+ derefs_needed -= 1;
+ cur_expr = inner_expr;
+ } else {
+ break;
+ }
+ }
+
+ let derefs: String = iter::repeat('*').take(derefs_needed).collect();
+ db.span_suggestion(
+ param.span,
+ "try dereferencing",
+ format!("{}{}", derefs, snippet(cx, cur_expr.span, "<param>")),
+ );
+ }
+ },
+ )
+ }
+ }
+ }
+}
diff --git a/clippy_lints/src/utils/paths.rs b/clippy_lints/src/utils/paths.rs
index 12ef2f51d8c..474f16679a7 100644
--- a/clippy_lints/src/utils/paths.rs
+++ b/clippy_lints/src/utils/paths.rs
@@ -55,6 +55,7 @@ pub const LATE_CONTEXT: [&str; 4] = ["rustc", "lint", "context", "LateContext"];
pub const LINKED_LIST: [&str; 4] = ["alloc", "collections", "linked_list", "LinkedList"];
pub const LINT: [&str; 3] = ["rustc", "lint", "Lint"];
pub const LINT_ARRAY: [&str; 3] = ["rustc", "lint", "LintArray"];
+pub const MEM_DISCRIMINANT: [&str; 3] = ["core", "mem", "discriminant"];
pub const MEM_FORGET: [&str; 3] = ["core", "mem", "forget"];
pub const MEM_REPLACE: [&str; 3] = ["core", "mem", "replace"];
pub const MEM_UNINIT: [&str; 3] = ["core", "mem", "uninitialized"];
diff --git a/tests/ui/mem_discriminant.rs b/tests/ui/mem_discriminant.rs
new file mode 100644
index 00000000000..a7176fb7985
--- /dev/null
+++ b/tests/ui/mem_discriminant.rs
@@ -0,0 +1,44 @@
+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+
+#![deny(clippy::mem_discriminant_non_enum)]
+
+use std::mem;
+
+enum Foo {
+ One(usize),
+ Two(u8),
+}
+
+struct A(Foo);
+
+fn main() {
+ // bad
+ mem::discriminant(&"hello");
+ mem::discriminant(&&Some(2));
+ mem::discriminant(&&None::<u8>);
+ mem::discriminant(&&Foo::One(5));
+ mem::discriminant(&&Foo::Two(5));
+ mem::discriminant(&A(Foo::One(0)));
+
+ let ro = &Some(3);
+ let rro = &ro;
+ mem::discriminant(&ro);
+ mem::discriminant(rro);
+ mem::discriminant(&rro);
+
+
+ // ok
+ mem::discriminant(&Some(2));
+ mem::discriminant(&None::<u8>);
+ mem::discriminant(&Foo::One(5));
+ mem::discriminant(&Foo::Two(5));
+ mem::discriminant(ro);
+}
diff --git a/tests/ui/mem_discriminant.stderr b/tests/ui/mem_discriminant.stderr
new file mode 100644
index 00000000000..5255458d8f8
--- /dev/null
+++ b/tests/ui/mem_discriminant.stderr
@@ -0,0 +1,76 @@
+error: calling `mem::discriminant` on non-enum type `&str`
+ --> $DIR/mem_discriminant.rs:24:5
+ |
+24 | mem::discriminant(&"hello");
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+note: lint level defined here
+ --> $DIR/mem_discriminant.rs:11:9
+ |
+11 | #![deny(clippy::mem_discriminant_non_enum)]
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: calling `mem::discriminant` on non-enum type `&std::option::Option<i32>`
+ --> $DIR/mem_discriminant.rs:25:5
+ |
+25 | mem::discriminant(&&Some(2));
+ | ^^^^^^^^^^^^^^^^^^---------^
+ | |
+ | help: try dereferencing: `&Some(2)`
+
+error: calling `mem::discriminant` on non-enum type `&std::option::Option<u8>`
+ --> $DIR/mem_discriminant.rs:26:5
+ |
+26 | mem::discriminant(&&None::<u8>);
+ | ^^^^^^^^^^^^^^^^^^------------^
+ | |
+ | help: try dereferencing: `&None::<u8>`
+
+error: calling `mem::discriminant` on non-enum type `&Foo`
+ --> $DIR/mem_discriminant.rs:27:5
+ |
+27 | mem::discriminant(&&Foo::One(5));
+ | ^^^^^^^^^^^^^^^^^^-------------^
+ | |
+ | help: try dereferencing: `&Foo::One(5)`
+
+error: calling `mem::discriminant` on non-enum type `&Foo`
+ --> $DIR/mem_discriminant.rs:28:5
+ |
+28 | mem::discriminant(&&Foo::Two(5));
+ | ^^^^^^^^^^^^^^^^^^-------------^
+ | |
+ | help: try dereferencing: `&Foo::Two(5)`
+
+error: calling `mem::discriminant` on non-enum type `A`
+ --> $DIR/mem_discriminant.rs:29:5
+ |
+29 | mem::discriminant(&A(Foo::One(0)));
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: calling `mem::discriminant` on non-enum type `&std::option::Option<i32>`
+ --> $DIR/mem_discriminant.rs:33:5
+ |
+33 | mem::discriminant(&ro);
+ | ^^^^^^^^^^^^^^^^^^---^
+ | |
+ | help: try dereferencing: `ro`
+
+error: calling `mem::discriminant` on non-enum type `&std::option::Option<i32>`
+ --> $DIR/mem_discriminant.rs:34:5
+ |
+34 | mem::discriminant(rro);
+ | ^^^^^^^^^^^^^^^^^^---^
+ | |
+ | help: try dereferencing: `*rro`
+
+error: calling `mem::discriminant` on non-enum type `&&std::option::Option<i32>`
+ --> $DIR/mem_discriminant.rs:35:5
+ |
+35 | mem::discriminant(&rro);
+ | ^^^^^^^^^^^^^^^^^^----^
+ | |
+ | help: try dereferencing: `*rro`
+
+error: aborting due to 9 previous errors
+