Auto merge of rust-lang#11002 - y21:issue9422, r=Jarcho

teach `eager_or_lazy` about panicky arithmetic operations

Fixes rust-lang#9422
Fixes rust-lang#9814
Fixes rust-lang#11793

It's a bit sad that we have to do this because arithmetic operations seemed to me like the prime example where a closure would not be necessary, but this has "side effects" (changes behavior when going from lazy to eager) as some of these panic on overflow/underflow if compiled with `-Coverflow-checks` (which is the default in debug mode).
Given the number of backlinks in the mentioned issues, this seems to be a FP that is worth fixing, probably.

changelog: [`unnecessary_lazy_evaluations`]: don't lint if closure has panicky arithmetic operations

Author: bors

Diff for: clippy_lints/src/matches/match_same_arms.rs

@@ -1,4 +1,4 @@
-use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::diagnostics::span_lint_hir_and_then;
 use clippy_utils::source::snippet;
 use clippy_utils::{is_lint_allowed, path_to_local, search_same, SpanlessEq, SpanlessHash};
 use core::cmp::Ordering;
@@ -104,9 +104,10 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
             if !cx.tcx.features().non_exhaustive_omitted_patterns_lint
                 || is_lint_allowed(cx, NON_EXHAUSTIVE_OMITTED_PATTERNS, arm2.hir_id)
             {
-                span_lint_and_then(
+                span_lint_hir_and_then(
                     cx,
                     MATCH_SAME_ARMS,
+                    arm1.hir_id,
                     arm1.span,
                     "this match arm has an identical body to the `_` wildcard arm",
                     |diag| {
@@ -124,9 +125,10 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'_>]) {
                 (arm2, arm1)
             };
 
-            span_lint_and_then(
+            span_lint_hir_and_then(
                 cx,
                 MATCH_SAME_ARMS,
+                keep_arm.hir_id,
                 keep_arm.span,
                 "this match arm has an identical body to another arm",
                 |diag| {

Diff for: clippy_utils/src/consts.rs

@@ -10,7 +10,7 @@ use rustc_hir::{BinOp, BinOpKind, Block, ConstBlock, Expr, ExprKind, HirId, Item
 use rustc_lexer::tokenize;
 use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::{alloc_range, Scalar};
-use rustc_middle::ty::{self, EarlyBinder, FloatTy, GenericArgsRef, List, ScalarInt, Ty, TyCtxt};
+use rustc_middle::ty::{self, EarlyBinder, FloatTy, GenericArgsRef, IntTy, List, ScalarInt, Ty, TyCtxt, UintTy};
 use rustc_middle::{bug, mir, span_bug};
 use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::SyntaxContext;
@@ -51,6 +51,63 @@ pub enum Constant<'tcx> {
     Err,
 }
 
+trait IntTypeBounds: Sized {
+    type Output: PartialOrd;
+
+    fn min_max(self) -> Option<(Self::Output, Self::Output)>;
+    fn bits(self) -> Self::Output;
+    fn ensure_fits(self, val: Self::Output) -> Option<Self::Output> {
+        let (min, max) = self.min_max()?;
+        (min <= val && val <= max).then_some(val)
+    }
+}
+impl IntTypeBounds for UintTy {
+    type Output = u128;
+    fn min_max(self) -> Option<(Self::Output, Self::Output)> {
+        Some(match self {
+            UintTy::U8 => (u8::MIN.into(), u8::MAX.into()),
+            UintTy::U16 => (u16::MIN.into(), u16::MAX.into()),
+            UintTy::U32 => (u32::MIN.into(), u32::MAX.into()),
+            UintTy::U64 => (u64::MIN.into(), u64::MAX.into()),
+            UintTy::U128 => (u128::MIN, u128::MAX),
+            UintTy::Usize => (usize::MIN.try_into().ok()?, usize::MAX.try_into().ok()?),
+        })
+    }
+    fn bits(self) -> Self::Output {
+        match self {
+            UintTy::U8 => 8,
+            UintTy::U16 => 16,
+            UintTy::U32 => 32,
+            UintTy::U64 => 64,
+            UintTy::U128 => 128,
+            UintTy::Usize => usize::BITS.into(),
+        }
+    }
+}
+impl IntTypeBounds for IntTy {
+    type Output = i128;
+    fn min_max(self) -> Option<(Self::Output, Self::Output)> {
+        Some(match self {
+            IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
+            IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
+            IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
+            IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
+            IntTy::I128 => (i128::MIN, i128::MAX),
+            IntTy::Isize => (isize::MIN.try_into().ok()?, isize::MAX.try_into().ok()?),
+        })
+    }
+    fn bits(self) -> Self::Output {
+        match self {
+            IntTy::I8 => 8,
+            IntTy::I16 => 16,
+            IntTy::I32 => 32,
+            IntTy::I64 => 64,
+            IntTy::I128 => 128,
+            IntTy::Isize => isize::BITS.into(),
+        }
+    }
+}
+
 impl<'tcx> PartialEq for Constant<'tcx> {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {
@@ -433,8 +490,15 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
         match *o {
             Int(value) => {
                 let ty::Int(ity) = *ty.kind() else { return None };
+                let (min, _) = ity.min_max()?;
                 // sign extend
                 let value = sext(self.lcx.tcx, value, ity);
+
+                // Applying unary - to the most negative value of any signed integer type panics.
+                if value == min {
+                    return None;
+                }
+
                 let value = value.checked_neg()?;
                 // clear unused bits
                 Some(Int(unsext(self.lcx.tcx, value, ity)))
@@ -570,17 +634,33 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
         match (l, r) {
             (Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck_results.expr_ty_opt(left)?.kind() {
                 ty::Int(ity) => {
+                    let (ty_min_value, _) = ity.min_max()?;
+                    let bits = ity.bits();
                     let l = sext(self.lcx.tcx, l, ity);
                     let r = sext(self.lcx.tcx, r, ity);
+
+                    // Using / or %, where the left-hand argument is the smallest integer of a signed integer type and
+                    // the right-hand argument is -1 always panics, even with overflow-checks disabled
+                    if let BinOpKind::Div | BinOpKind::Rem = op.node
+                        && l == ty_min_value
+                        && r == -1
+                    {
+                        return None;
+                    }
+
                     let zext = |n: i128| Constant::Int(unsext(self.lcx.tcx, n, ity));
                     match op.node {
-                        BinOpKind::Add => l.checked_add(r).map(zext),
-                        BinOpKind::Sub => l.checked_sub(r).map(zext),
-                        BinOpKind::Mul => l.checked_mul(r).map(zext),
+                        // When +, * or binary - create a value greater than the maximum value, or less than
+                        // the minimum value that can be stored, it panics.
+                        BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(zext),
+                        BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(zext),
+                        BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(zext),
                         BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
                         BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
-                        BinOpKind::Shr => l.checked_shr(r.try_into().ok()?).map(zext),
-                        BinOpKind::Shl => l.checked_shl(r.try_into().ok()?).map(zext),
+                        // Using << or >> where the right-hand argument is greater than or equal to the number of bits
+                        // in the type of the left-hand argument, or is negative panics.
+                        BinOpKind::Shr if r < bits && !r.is_negative() => l.checked_shr(r.try_into().ok()?).map(zext),
+                        BinOpKind::Shl if r < bits && !r.is_negative() => l.checked_shl(r.try_into().ok()?).map(zext),
                         BinOpKind::BitXor => Some(zext(l ^ r)),
                         BinOpKind::BitOr => Some(zext(l | r)),
                         BinOpKind::BitAnd => Some(zext(l & r)),
@@ -593,24 +673,28 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                         _ => None,
                     }
                 },
-                ty::Uint(_) => match op.node {
-                    BinOpKind::Add => l.checked_add(r).map(Constant::Int),
-                    BinOpKind::Sub => l.checked_sub(r).map(Constant::Int),
-                    BinOpKind::Mul => l.checked_mul(r).map(Constant::Int),
-                    BinOpKind::Div => l.checked_div(r).map(Constant::Int),
-                    BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
-                    BinOpKind::Shr => l.checked_shr(r.try_into().ok()?).map(Constant::Int),
-                    BinOpKind::Shl => l.checked_shl(r.try_into().ok()?).map(Constant::Int),
-                    BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
-                    BinOpKind::BitOr => Some(Constant::Int(l | r)),
-                    BinOpKind::BitAnd => Some(Constant::Int(l & r)),
-                    BinOpKind::Eq => Some(Constant::Bool(l == r)),
-                    BinOpKind::Ne => Some(Constant::Bool(l != r)),
-                    BinOpKind::Lt => Some(Constant::Bool(l < r)),
-                    BinOpKind::Le => Some(Constant::Bool(l <= r)),
-                    BinOpKind::Ge => Some(Constant::Bool(l >= r)),
-                    BinOpKind::Gt => Some(Constant::Bool(l > r)),
-                    _ => None,
+                ty::Uint(ity) => {
+                    let bits = ity.bits();
+
+                    match op.node {
+                        BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
+                        BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
+                        BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
+                        BinOpKind::Div => l.checked_div(r).map(Constant::Int),
+                        BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
+                        BinOpKind::Shr if r < bits => l.checked_shr(r.try_into().ok()?).map(Constant::Int),
+                        BinOpKind::Shl if r < bits => l.checked_shl(r.try_into().ok()?).map(Constant::Int),
+                        BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
+                        BinOpKind::BitOr => Some(Constant::Int(l | r)),
+                        BinOpKind::BitAnd => Some(Constant::Int(l & r)),
+                        BinOpKind::Eq => Some(Constant::Bool(l == r)),
+                        BinOpKind::Ne => Some(Constant::Bool(l != r)),
+                        BinOpKind::Lt => Some(Constant::Bool(l < r)),
+                        BinOpKind::Le => Some(Constant::Bool(l <= r)),
+                        BinOpKind::Ge => Some(Constant::Bool(l >= r)),
+                        BinOpKind::Gt => Some(Constant::Bool(l > r)),
+                        _ => None,
+                    }
                 },
                 _ => None,
             },

Diff for: clippy_utils/src/eager_or_lazy.rs

@@ -9,12 +9,13 @@
 //!  - or-fun-call
 //!  - option-if-let-else
 
+use crate::consts::{constant, FullInt};
 use crate::ty::{all_predicates_of, is_copy};
 use crate::visitors::is_const_evaluatable;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_expr, Visitor};
-use rustc_hir::{Block, Expr, ExprKind, QPath, UnOp};
+use rustc_hir::{BinOpKind, Block, Expr, ExprKind, QPath, UnOp};
 use rustc_lint::LateContext;
 use rustc_middle::ty;
 use rustc_middle::ty::adjustment::Adjust;
@@ -193,6 +194,12 @@ fn expr_eagerness<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> EagernessS
                         self.eagerness = Lazy;
                     }
                 },
+
+                // `-i32::MIN` panics with overflow checks
+                ExprKind::Unary(UnOp::Neg, right) if constant(self.cx, self.cx.typeck_results(), right).is_none() => {
+                    self.eagerness |= NoChange;
+                },
+
                 // Custom `Deref` impl might have side effects
                 ExprKind::Unary(UnOp::Deref, e)
                     if self.cx.typeck_results().expr_ty(e).builtin_deref(true).is_none() =>
@@ -207,6 +214,49 @@ fn expr_eagerness<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> EagernessS
                         self.cx.typeck_results().expr_ty(e).kind(),
                         ty::Bool | ty::Int(_) | ty::Uint(_),
                     ) => {},
+
+                // `>>` and `<<` panic when the right-hand side is greater than or equal to the number of bits in the
+                // type of the left-hand side, or is negative.
+                // We intentionally only check if the right-hand isn't a constant, because even if the suggestion would
+                // overflow with constants, the compiler emits an error for it and the programmer will have to fix it.
+                // Thus, we would realistically only delay the lint.
+                ExprKind::Binary(op, _, right)
+                    if matches!(op.node, BinOpKind::Shl | BinOpKind::Shr)
+                        && constant(self.cx, self.cx.typeck_results(), right).is_none() =>
+                {
+                    self.eagerness |= NoChange;
+                },
+
+                ExprKind::Binary(op, left, right)
+                    if matches!(op.node, BinOpKind::Div | BinOpKind::Rem)
+                        && let right_ty = self.cx.typeck_results().expr_ty(right)
+                        && let left = constant(self.cx, self.cx.typeck_results(), left)
+                        && let right = constant(self.cx, self.cx.typeck_results(), right)
+                            .and_then(|c| c.int_value(self.cx, right_ty))
+                        && matches!(
+                            (left, right),
+                            // `1 / x`: x might be zero
+                            (_, None)
+                            // `x / -1`: x might be T::MIN
+                            | (None, Some(FullInt::S(-1)))
+                        ) =>
+                {
+                    self.eagerness |= NoChange;
+                },
+
+                // Similar to `>>` and `<<`, we only want to avoid linting entirely if either side is unknown and the
+                // compiler can't emit an error for an overflowing expression.
+                // Suggesting eagerness for `true.then(|| i32::MAX + 1)` is okay because the compiler will emit an
+                // error and it's good to have the eagerness warning up front when the user fixes the logic error.
+                ExprKind::Binary(op, left, right)
+                    if matches!(op.node, BinOpKind::Add | BinOpKind::Sub | BinOpKind::Mul)
+                        && !self.cx.typeck_results().expr_ty(e).is_floating_point()
+                        && (constant(self.cx, self.cx.typeck_results(), left).is_none()
+                            || constant(self.cx, self.cx.typeck_results(), right).is_none()) =>
+                {
+                    self.eagerness |= NoChange;
+                },
+
                 ExprKind::Binary(_, lhs, rhs)
                     if self.cx.typeck_results().expr_ty(lhs).is_primitive()
                         && self.cx.typeck_results().expr_ty(rhs).is_primitive() => {},

Diff for: tests/ui/unnecessary_lazy_eval.fixed

@@ -6,6 +6,8 @@
 #![allow(clippy::needless_borrow)]
 #![allow(clippy::unnecessary_literal_unwrap)]
 #![allow(clippy::unit_arg)]
+#![allow(arithmetic_overflow)]
+#![allow(unconditional_panic)]
 
 use std::ops::Deref;
 
@@ -190,3 +192,79 @@ fn issue9485() {
     // should not lint, is in proc macro
     with_span!(span Some(42).unwrap_or_else(|| 2););
 }
+
+fn issue9422(x: usize) -> Option<usize> {
+    (x >= 5).then(|| x - 5)
+    // (x >= 5).then_some(x - 5)  // clippy suggestion panics
+}
+
+fn panicky_arithmetic_ops(x: usize, y: isize) {
+    #![allow(clippy::identity_op, clippy::eq_op)]
+
+    // See comments in `eager_or_lazy.rs` for the rules that this is meant to follow
+
+    let _x = false.then_some(i32::MAX + 1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(i32::MAX * 2);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(i32::MAX - 1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(i32::MIN - 1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some((1 + 2 * 3 - 2 / 3 + 9) << 2);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(255u8 << 7);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(255u8 << 8);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(255u8 >> 8);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then(|| 255u8 >> x);
+    let _x = false.then_some(i32::MAX + -1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(-i32::MAX);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(-i32::MIN);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then(|| -y);
+    let _x = false.then_some(255 >> -7);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(255 << -1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(1 / 0);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(x << -1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(x << 2);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then(|| x + x);
+    let _x = false.then(|| x * x);
+    let _x = false.then(|| x - x);
+    let _x = false.then(|| x / x);
+    let _x = false.then(|| x % x);
+    let _x = false.then(|| x + 1);
+    let _x = false.then(|| 1 + x);
+
+    let _x = false.then_some(x / 0);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(x % 0);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then(|| y / -1);
+    let _x = false.then_some(1 / -1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(i32::MIN / -1);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then(|| i32::MIN / x as i32);
+    let _x = false.then_some(i32::MIN / 0);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then_some(4 / 2);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+    let _x = false.then(|| 1 / x);
+
+    // const eval doesn't read variables, but floating point math never panics, so we can still emit a
+    // warning
+    let f1 = 1.0;
+    let f2 = 2.0;
+    let _x = false.then_some(f1 + f2);
+    //~^ ERROR: unnecessary closure used with `bool::then`
+}