Auto merge of #52018 - flip1995:rfc2103, r=oli-obk

Implementation of tool lints.

Tracking issue: #44690

src/doc/unstable-book/src/language-features/tool-lints.md

@@ -0,0 +1,35 @@
+# `tool_lints`
+
+The tracking issue for this feature is: [#44690]
+
+[#44690]: https://github.com/rust-lang/rust/issues/44690
+
+------------------------
+
+Tool lints let you use scoped lints, to `allow`, `warn`, `deny` or `forbid` lints of
+certain tools.
+
+Currently `clippy` is the only available lint tool.
+
+It is recommended for lint tools to implement the scoped lints like this:
+
+- `#[_(TOOL_NAME::lintname)]`: for lint names
+- `#[_(TOOL_NAME::lintgroup)]`: for groups of lints
+- `#[_(TOOL_NAME::all)]`: for (almost[^1]) all lints
+
+## An example
+
+```rust
+#![feature(tool_lints)]
+
+#![warn(clippy::pedantic)]
+
+#[allow(clippy::filter_map)]
+fn main() {
+    let v = vec![0; 10];
+    let _ = v.into_iter().filter(|&x| x < 1).map(|x| x + 1).collect::<Vec<_>>();
+    println!("No filter_map()!");
+}
+```
+
+[^1]: Some defined lint groups can be excluded here.

src/librustc/diagnostics.rs

@@ -2137,4 +2137,5 @@ register_diagnostics! {
     E0707, // multiple elided lifetimes used in arguments of `async fn`
     E0708, // `async` non-`move` closures with arguments are not currently supported
     E0709, // multiple different lifetimes used in arguments of `async fn`
+    E0710, // an unknown tool name found in scoped lint
 }

src/librustc/lint/levels.rs

@@ -22,6 +22,7 @@ use session::Session;
 use syntax::ast;
 use syntax::attr;
 use syntax::codemap::MultiSpan;
+use syntax::feature_gate;
 use syntax::symbol::Symbol;
 use util::nodemap::FxHashMap;
 
@@ -221,6 +222,28 @@ impl<'a> LintLevelsBuilder<'a> {
                         continue
                     }
                 };
+                if let Some(lint_tool) = word.is_scoped() {
+                    if !self.sess.features_untracked().tool_lints {
+                        feature_gate::emit_feature_err(&sess.parse_sess,
+                                                       "tool_lints",
+                                                       word.span,
+                                                       feature_gate::GateIssue::Language,
+                                                       &format!("scoped lint `{}` is experimental",
+                                                                word.ident));
+                    }
+
+                    if !attr::is_known_lint_tool(lint_tool) {
+                        span_err!(
+                            sess,
+                            lint_tool.span,
+                            E0710,
+                            "an unknown tool name found in scoped lint: `{}`",
+                            word.ident
+                        );
+                    }
+
+                    continue
+                }
                 let name = word.name();
                 match store.check_lint_name(&name.as_str()) {
                     CheckLintNameResult::Ok(ids) => {

src/libsyntax/attr/mod.rs

@@ -90,13 +90,18 @@ pub fn is_known(attr: &Attribute) -> bool {
 }
 
 const RUST_KNOWN_TOOL: &[&str] = &["clippy", "rustfmt"];
+const RUST_KNOWN_LINT_TOOL: &[&str] = &["clippy"];
 
 pub fn is_known_tool(attr: &Attribute) -> bool {
     let tool_name =
         attr.path.segments.iter().next().expect("empty path in attribute").ident.name;
     RUST_KNOWN_TOOL.contains(&tool_name.as_str().as_ref())
 }
 
+pub fn is_known_lint_tool(m_item: Ident) -> bool {
+    RUST_KNOWN_LINT_TOOL.contains(&m_item.as_str().as_ref())
+}
+
 impl NestedMetaItem {
     /// Returns the MetaItem if self is a NestedMetaItemKind::MetaItem.
     pub fn meta_item(&self) -> Option<&MetaItem> {
@@ -290,6 +295,14 @@ impl MetaItem {
     pub fn is_meta_item_list(&self) -> bool {
         self.meta_item_list().is_some()
     }
+
+    pub fn is_scoped(&self) -> Option<Ident> {
+        if self.ident.segments.len() > 1 {
+            Some(self.ident.segments[0].ident)
+        } else {
+            None
+        }
+    }
 }
 
 impl Attribute {

src/libsyntax/feature_gate.rs

@@ -458,6 +458,8 @@ declare_features! (
 
     // Scoped attributes
     (active, tool_attributes, "1.25.0", Some(44690), None),
+    // Scoped lints
+    (active, tool_lints, "1.28.0", Some(44690), None),
 
     // allow irrefutable patterns in if-let and while-let statements (RFC 2086)
     (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),

src/test/compile-fail/feature-gate-tool_lints.rs

@@ -0,0 +1,12 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+#[warn(clippy::assign_ops)] //~ ERROR scoped lint `clippy::assign_ops` is experimental
+fn main() {}

src/test/compile-fail/tool_lints.rs

@@ -0,0 +1,18 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+// Don't allow tool_lints, which aren't scoped
+
+#![feature(tool_lints)]
+#![deny(unknown_lints)]
+
+#![deny(clippy)] //~ ERROR: unknown lint: `clippy`
+
+fn main() {}

src/test/compile-fail/unknown-lint-tool-name.rs

@@ -0,0 +1,16 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+#![feature(tool_lints)]
+
+#![deny(foo::bar)] //~ ERROR an unknown tool name found in scoped lint: `foo::bar`
+
+#[allow(foo::bar)] //~ ERROR an unknown tool name found in scoped lint: `foo::bar`
+fn main() {}

src/test/run-pass/tool_lints.rs

@@ -0,0 +1,15 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+#![feature(tool_lints)]
+#![deny(unknown_lints)]
+
+#[allow(clippy::almost_swapped)]
+fn main() {}

src/test/run-pass/tool_lints_2018_preview.rs

@@ -0,0 +1,16 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+#![feature(tool_lints)]
+#![feature(rust_2018_preview)]
+#![deny(unknown_lints)]
+
+#[allow(clippy::almost_swapped)]
+fn main() {}

src/test/ui/feature-gate-tool_lints.rs

@@ -0,0 +1,15 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+#[warn(clippy::decimal_literal_representation)]
+//~^ ERROR scoped lint `clippy::decimal_literal_representation` is experimental
+fn main() {
+    let a = 65_535;
+}

src/test/ui/feature-gate-tool_lints.stderr

@@ -0,0 +1,11 @@
+error[E0658]: scoped lint `clippy::decimal_literal_representation` is experimental (see issue #44690)
+  --> $DIR/feature-gate-tool_lints.rs:11:8
+   |
+LL | #[warn(clippy::decimal_literal_representation)]
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add #![feature(tool_lints)] to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.

src/test/ui/tool_lints.rs

@@ -0,0 +1,15 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// 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.
+
+#![feature(tool_lints)]
+
+#[warn(foo::bar)]
+//~^ ERROR an unknown tool name found in scoped lint: `foo::bar`
+fn main() {}

src/test/ui/tool_lints.stderr

@@ -0,0 +1,9 @@
+error[E0710]: an unknown tool name found in scoped lint: `foo::bar`
+  --> $DIR/tool_lints.rs:13:8
+   |
+LL | #[warn(foo::bar)]
+   |        ^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0710`.