Rollup of 4 pull requests

.github/workflows/clippy_bors.yml

@@ -128,14 +128,14 @@ jobs:
         SYSROOT=$(rustc --print sysroot)
         echo "$SYSROOT/bin" >> $GITHUB_PATH
 
-    - name: Build
-      run: cargo build --features deny-warnings
+    - name: Build with internal lints
+      run: cargo build --features deny-warnings,internal-lints
 
-    - name: Test
-      run: cargo test --features deny-warnings
+    - name: Test with internal lints
+      run: cargo test --features deny-warnings,internal-lints
 
-    - name: Test clippy_lints
-      run: cargo test --features deny-warnings
+    - name: Test clippy_lints with internal lints
+      run: cargo test --features deny-warnings,internal-lints
       working-directory: clippy_lints
 
     - name: Test rustc_tools_util

CHANGELOG.md

@@ -1770,6 +1770,7 @@ Released 2018-09-13
 [`cmp_owned`]: https://rust-lang.github.io/rust-clippy/master/index.html#cmp_owned
 [`cognitive_complexity`]: https://rust-lang.github.io/rust-clippy/master/index.html#cognitive_complexity
 [`collapsible_if`]: https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_if
+[`collapsible_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#collapsible_match
 [`comparison_chain`]: https://rust-lang.github.io/rust-clippy/master/index.html#comparison_chain
 [`comparison_to_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#comparison_to_empty
 [`copy_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#copy_iterator

CONTRIBUTING.md

@@ -14,11 +14,16 @@ All contributors are expected to follow the [Rust Code of Conduct].
 
 - [Contributing to Clippy](#contributing-to-clippy)
   - [Getting started](#getting-started)
+    - [High level approach](#high-level-approach)
     - [Finding something to fix/improve](#finding-something-to-fiximprove)
   - [Writing code](#writing-code)
   - [Getting code-completion for rustc internals to work](#getting-code-completion-for-rustc-internals-to-work)
   - [How Clippy works](#how-clippy-works)
   - [Fixing build failures caused by Rust](#fixing-build-failures-caused-by-rust)
+    - [Patching git-subtree to work with big repos](#patching-git-subtree-to-work-with-big-repos)
+    - [Performing the sync](#performing-the-sync)
+    - [Syncing back changes in Clippy to [`rust-lang/rust`]](#syncing-back-changes-in-clippy-to-rust-langrust)
+    - [Defining remotes](#defining-remotes)
   - [Issue and PR triage](#issue-and-pr-triage)
   - [Bors and Homu](#bors-and-homu)
   - [Contributions](#contributions)
@@ -320,8 +325,8 @@ commands [here][homu_instructions].
 [l-crash]: https://github.com/rust-lang/rust-clippy/labels/L-crash
 [l-bug]: https://github.com/rust-lang/rust-clippy/labels/L-bug
 [homu]: https://github.com/rust-lang/homu
-[homu_instructions]: https://buildbot2.rust-lang.org/homu/
-[homu_queue]: https://buildbot2.rust-lang.org/homu/queue/clippy
+[homu_instructions]: https://bors.rust-lang.org/
+[homu_queue]: https://bors.rust-lang.org/queue/clippy
 
 ## Contributions
 

Cargo.toml

@@ -32,7 +32,7 @@ path = "src/driver.rs"
 clippy_lints = { version = "0.0.212", path = "clippy_lints" }
 # end automatic update
 semver = "0.11"
-rustc_tools_util = { version = "0.2.0", path = "rustc_tools_util"}
+rustc_tools_util = { version = "0.2.0", path = "rustc_tools_util" }
 tempfile = { version = "3.1.0", optional = true }
 
 [dev-dependencies]
@@ -49,8 +49,9 @@ derive-new = "0.5"
 rustc-workspace-hack = "1.0.0"
 
 [build-dependencies]
-rustc_tools_util = { version = "0.2.0", path = "rustc_tools_util"}
+rustc_tools_util = { version = "0.2.0", path = "rustc_tools_util" }
 
 [features]
 deny-warnings = []
 integration = ["tempfile"]
+internal-lints = ["clippy_lints/internal-lints"]

clippy_dev/src/lib.rs

@@ -146,16 +146,30 @@ pub fn gen_deprecated<'a>(lints: impl Iterator<Item = &'a Lint>) -> Vec<String>
 }
 
 #[must_use]
-pub fn gen_register_lint_list<'a>(lints: impl Iterator<Item = &'a Lint>) -> Vec<String> {
-    let pre = "    store.register_lints(&[".to_string();
-    let post = "    ]);".to_string();
-    let mut inner = lints
+pub fn gen_register_lint_list<'a>(
+    internal_lints: impl Iterator<Item = &'a Lint>,
+    usable_lints: impl Iterator<Item = &'a Lint>,
+) -> Vec<String> {
+    let header = "    store.register_lints(&[".to_string();
+    let footer = "    ]);".to_string();
+    let internal_lints = internal_lints
+        .sorted_by_key(|l| format!("        &{}::{},", l.module, l.name.to_uppercase()))
+        .map(|l| {
+            format!(
+                "        #[cfg(feature = \"internal-lints\")]\n        &{}::{},",
+                l.module,
+                l.name.to_uppercase()
+            )
+        });
+    let other_lints = usable_lints
+        .sorted_by_key(|l| format!("        &{}::{},", l.module, l.name.to_uppercase()))
         .map(|l| format!("        &{}::{},", l.module, l.name.to_uppercase()))
-        .sorted()
-        .collect::<Vec<String>>();
-    inner.insert(0, pre);
-    inner.push(post);
-    inner
+        .sorted();
+    let mut lint_list = vec![header];
+    lint_list.extend(internal_lints);
+    lint_list.extend(other_lints);
+    lint_list.push(footer);
+    lint_list
 }
 
 /// Gathers all files in `src/clippy_lints` and gathers all lints inside

clippy_dev/src/update_lints.rs

@@ -68,7 +68,7 @@ pub fn run(update_mode: UpdateMode) {
         "end register lints",
         false,
         update_mode == UpdateMode::Change,
-        || gen_register_lint_list(usable_lints.iter().chain(internal_lints.iter())),
+        || gen_register_lint_list(internal_lints.iter(), usable_lints.iter()),
     )
     .changed;
 

clippy_lints/Cargo.toml

@@ -28,6 +28,7 @@ smallvec = { version = "1", features = ["union"] }
 toml = "0.5.3"
 unicode-normalization = "0.1"
 semver = "0.11"
+rustc-semver="1.1.0"
 # NOTE: cargo requires serde feat in its url dep
 # see <https://github.com/rust-lang/rust/pull/63587#issuecomment-522343864>
 url = { version =  "2.1.0", features = ["serde"] }
@@ -36,3 +37,5 @@ syn = { version = "1", features = ["full"] }
 
 [features]
 deny-warnings = []
+# build clippy with internal lints enabled, off by default
+internal-lints = []

clippy_lints/src/collapsible_match.rs

@@ -0,0 +1,172 @@
+use crate::utils::visitors::LocalUsedVisitor;
+use crate::utils::{span_lint_and_then, SpanlessEq};
+use if_chain::if_chain;
+use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
+use rustc_hir::{Arm, Expr, ExprKind, Guard, HirId, Pat, PatKind, QPath, StmtKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::{DefIdTree, TyCtxt};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{MultiSpan, Span};
+
+declare_clippy_lint! {
+    /// **What it does:** Finds nested `match` or `if let` expressions where the patterns may be "collapsed" together
+    /// without adding any branches.
+    ///
+    /// Note that this lint is not intended to find _all_ cases where nested match patterns can be merged, but only
+    /// cases where merging would most likely make the code more readable.
+    ///
+    /// **Why is this bad?** It is unnecessarily verbose and complex.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    ///
+    /// ```rust
+    /// fn func(opt: Option<Result<u64, String>>) {
+    ///     let n = match opt {
+    ///         Some(n) => match n {
+    ///             Ok(n) => n,
+    ///             _ => return,
+    ///         }
+    ///         None => return,
+    ///     };
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// fn func(opt: Option<Result<u64, String>>) {
+    ///     let n = match opt {
+    ///         Some(Ok(n)) => n,
+    ///         _ => return,
+    ///     };
+    /// }
+    /// ```
+    pub COLLAPSIBLE_MATCH,
+    style,
+    "Nested `match` or `if let` expressions where the patterns may be \"collapsed\" together."
+}
+
+declare_lint_pass!(CollapsibleMatch => [COLLAPSIBLE_MATCH]);
+
+impl<'tcx> LateLintPass<'tcx> for CollapsibleMatch {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
+        if let ExprKind::Match(_expr, arms, _source) = expr.kind {
+            if let Some(wild_arm) = arms.iter().rfind(|arm| arm_is_wild_like(arm, cx.tcx)) {
+                for arm in arms {
+                    check_arm(arm, wild_arm, cx);
+                }
+            }
+        }
+    }
+}
+
+fn check_arm(arm: &Arm<'_>, wild_outer_arm: &Arm<'_>, cx: &LateContext<'_>) {
+    if_chain! {
+        let expr = strip_singleton_blocks(arm.body);
+        if let ExprKind::Match(expr_in, arms_inner, _) = expr.kind;
+        // the outer arm pattern and the inner match
+        if expr_in.span.ctxt() == arm.pat.span.ctxt();
+        // there must be no more than two arms in the inner match for this lint
+        if arms_inner.len() == 2;
+        // no if guards on the inner match
+        if arms_inner.iter().all(|arm| arm.guard.is_none());
+        // match expression must be a local binding
+        // match <local> { .. }
+        if let ExprKind::Path(QPath::Resolved(None, path)) = expr_in.kind;
+        if let Res::Local(binding_id) = path.res;
+        // one of the branches must be "wild-like"
+        if let Some(wild_inner_arm_idx) = arms_inner.iter().rposition(|arm_inner| arm_is_wild_like(arm_inner, cx.tcx));
+        let (wild_inner_arm, non_wild_inner_arm) =
+            (&arms_inner[wild_inner_arm_idx], &arms_inner[1 - wild_inner_arm_idx]);
+        if !pat_contains_or(non_wild_inner_arm.pat);
+        // the binding must come from the pattern of the containing match arm
+        // ..<local>.. => match <local> { .. }
+        if let Some(binding_span) = find_pat_binding(arm.pat, binding_id);
+        // the "wild-like" branches must be equal
+        if SpanlessEq::new(cx).eq_expr(wild_inner_arm.body, wild_outer_arm.body);
+        // the binding must not be used in the if guard
+        if !matches!(arm.guard, Some(Guard::If(guard)) if LocalUsedVisitor::new(binding_id).check_expr(guard));
+        // ...or anywhere in the inner match
+        if !arms_inner.iter().any(|arm| LocalUsedVisitor::new(binding_id).check_arm(arm));
+        then {
+            span_lint_and_then(
+                cx,
+                COLLAPSIBLE_MATCH,
+                expr.span,
+                "Unnecessary nested match",
+                |diag| {
+                    let mut help_span = MultiSpan::from_spans(vec![binding_span, non_wild_inner_arm.pat.span]);
+                    help_span.push_span_label(binding_span, "Replace this binding".into());
+                    help_span.push_span_label(non_wild_inner_arm.pat.span, "with this pattern".into());
+                    diag.span_help(help_span, "The outer pattern can be modified to include the inner pattern.");
+                },
+            );
+        }
+    }
+}
+
+fn strip_singleton_blocks<'hir>(mut expr: &'hir Expr<'hir>) -> &'hir Expr<'hir> {
+    while let ExprKind::Block(block, _) = expr.kind {
+        match (block.stmts, block.expr) {
+            ([stmt], None) => match stmt.kind {
+                StmtKind::Expr(e) | StmtKind::Semi(e) => expr = e,
+                _ => break,
+            },
+            ([], Some(e)) => expr = e,
+            _ => break,
+        }
+    }
+    expr
+}
+
+/// A "wild-like" pattern is wild ("_") or `None`.
+/// For this lint to apply, both the outer and inner match expressions
+/// must have "wild-like" branches that can be combined.
+fn arm_is_wild_like(arm: &Arm<'_>, tcx: TyCtxt<'_>) -> bool {
+    if arm.guard.is_some() {
+        return false;
+    }
+    match arm.pat.kind {
+        PatKind::Binding(..) | PatKind::Wild => true,
+        PatKind::Path(QPath::Resolved(None, path)) if is_none_ctor(path.res, tcx) => true,
+        _ => false,
+    }
+}
+
+fn find_pat_binding(pat: &Pat<'_>, hir_id: HirId) -> Option<Span> {
+    let mut span = None;
+    pat.walk_short(|p| match &p.kind {
+        // ignore OR patterns
+        PatKind::Or(_) => false,
+        PatKind::Binding(_bm, _, _ident, _) => {
+            let found = p.hir_id == hir_id;
+            if found {
+                span = Some(p.span);
+            }
+            !found
+        },
+        _ => true,
+    });
+    span
+}
+
+fn pat_contains_or(pat: &Pat<'_>) -> bool {
+    let mut result = false;
+    pat.walk(|p| {
+        let is_or = matches!(p.kind, PatKind::Or(_));
+        result |= is_or;
+        !is_or
+    });
+    result
+}
+
+fn is_none_ctor(res: Res, tcx: TyCtxt<'_>) -> bool {
+    if let Some(none_id) = tcx.lang_items().option_none_variant() {
+        if let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Const), id) = res {
+            if let Some(variant_id) = tcx.parent(id) {
+                return variant_id == none_id;
+            }
+        }
+    }
+    false
+}

clippy_lints/src/default.rs

@@ -280,8 +280,7 @@ fn field_reassigned_by_stmt<'tcx>(this: &Stmt<'tcx>, binding_name: Symbol) -> Op
         // only take assignments to fields where the left-hand side field is a field of
         // the same binding as the previous statement
         if let ExprKind::Field(ref binding, field_ident) = assign_lhs.kind;
-        if let ExprKind::Path(ref qpath) = binding.kind;
-        if let QPath::Resolved(_, path) = qpath;
+        if let ExprKind::Path(QPath::Resolved(_, path)) = binding.kind;
         if let Some(second_binding_name) = path.segments.last();
         if second_binding_name.ident.name == binding_name;
         then {

clippy_lints/src/if_let_some_result.rs

@@ -41,8 +41,7 @@ declare_lint_pass!(OkIfLet => [IF_LET_SOME_RESULT]);
 impl<'tcx> LateLintPass<'tcx> for OkIfLet {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         if_chain! { //begin checking variables
-            if let ExprKind::Match(ref op, ref body, source) = expr.kind; //test if expr is a match
-            if let MatchSource::IfLetDesugar { .. } = source; //test if it is an If Let
+            if let ExprKind::Match(ref op, ref body, MatchSource::IfLetDesugar { .. }) = expr.kind; //test if expr is if let
             if let ExprKind::MethodCall(_, ok_span, ref result_types, _) = op.kind; //check is expr.ok() has type Result<T,E>.ok(, _)
             if let PatKind::TupleStruct(QPath::Resolved(_, ref x), ref y, _)  = body[0].pat.kind; //get operation
             if method_chain_args(op, &["ok"]).is_some(); //test to see if using ok() methoduse std::marker::Sized;

clippy_lints/src/implicit_return.rs

@@ -68,8 +68,7 @@ fn expr_match(cx: &LateContext<'_>, expr: &Expr<'_>) {
                 if_chain! {
                     if let StmtKind::Semi(expr, ..) = &stmt.kind;
                     // make sure it's a break, otherwise we want to skip
-                    if let ExprKind::Break(.., break_expr) = &expr.kind;
-                    if let Some(break_expr) = break_expr;
+                    if let ExprKind::Break(.., Some(break_expr)) = &expr.kind;
                     then {
                             lint(cx, expr.span, break_expr.span, LINT_BREAK);
                     }

clippy_lints/src/implicit_saturating_sub.rs

@@ -59,8 +59,7 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub {
             if let Some(target) = subtracts_one(cx, e);
 
             // Extracting out the variable name
-            if let ExprKind::Path(ref assign_path) = target.kind;
-            if let QPath::Resolved(_, ref ares_path) = assign_path;
+            if let ExprKind::Path(QPath::Resolved(_, ref ares_path)) = target.kind;
 
             then {
                 // Handle symmetric conditions in the if statement

clippy_lints/src/large_const_arrays.rs

@@ -52,8 +52,7 @@ impl<'tcx> LateLintPass<'tcx> for LargeConstArrays {
             if let ItemKind::Const(hir_ty, _) = &item.kind;
             let ty = hir_ty_to_ty(cx.tcx, hir_ty);
             if let ty::Array(element_type, cst) = ty.kind();
-            if let ConstKind::Value(val) = cst.val;
-            if let ConstValue::Scalar(element_count) = val;
+            if let ConstKind::Value(ConstValue::Scalar(element_count)) = cst.val;
             if let Ok(element_count) = element_count.to_machine_usize(&cx.tcx);
             if let Ok(element_size) = cx.layout_of(element_type).map(|l| l.size.bytes());
             if self.maximum_allowed_size < element_count * element_size;

clippy_lints/src/large_stack_arrays.rs

@@ -43,8 +43,7 @@ impl<'tcx> LateLintPass<'tcx> for LargeStackArrays {
         if_chain! {
             if let ExprKind::Repeat(_, _) = expr.kind;
             if let ty::Array(element_type, cst) = cx.typeck_results().expr_ty(expr).kind();
-            if let ConstKind::Value(val) = cst.val;
-            if let ConstValue::Scalar(element_count) = val;
+            if let ConstKind::Value(ConstValue::Scalar(element_count)) = cst.val;
             if let Ok(element_count) = element_count.to_machine_usize(&cx.tcx);
             if let Ok(element_size) = cx.layout_of(element_type).map(|l| l.size.bytes());
             if self.maximum_allowed_size < element_count * element_size;