Respect the configured MSRV in implicit_saturating_sub's if x != 0 { x -= 1 } rewrite

book/src/lint_configuration.md

@@ -941,6 +941,7 @@ The minimum rust version that the project supports. Defaults to the `rust-versio
 * [`filter_map_next`](https://rust-lang.github.io/rust-clippy/master/index.html#filter_map_next)
 * [`from_over_into`](https://rust-lang.github.io/rust-clippy/master/index.html#from_over_into)
 * [`if_then_some_else_none`](https://rust-lang.github.io/rust-clippy/master/index.html#if_then_some_else_none)
+* [`implicit_saturating_sub`](https://rust-lang.github.io/rust-clippy/master/index.html#implicit_saturating_sub)
 * [`index_refutable_slice`](https://rust-lang.github.io/rust-clippy/master/index.html#index_refutable_slice)
 * [`inefficient_to_string`](https://rust-lang.github.io/rust-clippy/master/index.html#inefficient_to_string)
 * [`io_other_error`](https://rust-lang.github.io/rust-clippy/master/index.html#io_other_error)

clippy_config/src/conf.rs

@@ -796,6 +796,7 @@ define_Conf! {
         filter_map_next,
         from_over_into,
         if_then_some_else_none,
+        implicit_saturating_sub,
         index_refutable_slice,
         inefficient_to_string,
         io_other_error,

clippy_lints/src/implicit_saturating_sub.rs

@@ -104,7 +104,7 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub {
             // Check if the conditional expression is a binary operation
             && let ExprKind::Binary(ref cond_op, cond_left, cond_right) = cond.kind
         {
-            check_with_condition(cx, expr, cond_op.node, cond_left, cond_right, then);
+            check_with_condition(cx, expr, cond_op.node, cond_left, cond_right, then, self.msrv);
         } else if let Some(higher::If {
             cond,
             then: if_block,
@@ -309,6 +309,7 @@ fn check_with_condition<'tcx>(
     cond_left: &Expr<'tcx>,
     cond_right: &Expr<'tcx>,
     then: &Expr<'tcx>,
+    msrv: Msrv,
 ) {
     // Ensure that the binary operator is >, !=, or <
     if (BinOpKind::Ne == cond_op || BinOpKind::Gt == cond_op || BinOpKind::Lt == cond_op)
@@ -342,6 +343,10 @@ fn check_with_condition<'tcx>(
             return;
         }
 
+        if is_in_const_context(cx) && !msrv.meets(cx, msrvs::SATURATING_SUB_CONST) {
+            return;
+        }
+
         // Get the variable name
         let var_name = ares_path.segments[0].ident.name;
         match cond_num_val.kind {

tests/ui/implicit_saturating_sub.fixed

@@ -278,3 +278,23 @@ fn wrongly_unmangled_macros() {
     let b = 20u64;
     let _ = test_big!(a).saturating_sub(test_little!(b));
 }
+
+#[clippy::msrv = "1.46.0"]
+pub const fn const_msrv_too_low(mut x: u32) -> u32 {
+    if x != 0 {
+        x -= 1;
+    }
+    x
+}
+
+#[clippy::msrv = "1.47.0"]
+pub const fn const_msrv_ok(mut x: u32) -> u32 {
+    x = x.saturating_sub(1);
+    x
+}
+
+#[clippy::msrv = "1.46.0"]
+pub fn nonconst_msrv_low(mut x: u32) -> u32 {
+    x = x.saturating_sub(1);
+    x
+}

tests/ui/implicit_saturating_sub.rs

@@ -357,3 +357,29 @@ fn wrongly_unmangled_macros() {
         0
     };
 }
+
+#[clippy::msrv = "1.46.0"]
+pub const fn const_msrv_too_low(mut x: u32) -> u32 {
+    if x != 0 {
+        x -= 1;
+    }
+    x
+}
+
+#[clippy::msrv = "1.47.0"]
+pub const fn const_msrv_ok(mut x: u32) -> u32 {
+    if x != 0 {
+        //~^ implicit_saturating_sub
+        x -= 1;
+    }
+    x
+}
+
+#[clippy::msrv = "1.46.0"]
+pub fn nonconst_msrv_low(mut x: u32) -> u32 {
+    if x != 0 {
+        //~^ implicit_saturating_sub
+        x -= 1;
+    }
+    x
+}

tests/ui/implicit_saturating_sub.stderr

@@ -256,5 +256,23 @@ LL | |         0
 LL | |     };
    | |_____^ help: replace it with: `test_big!(a).saturating_sub(test_little!(b))`
 
-error: aborting due to 29 previous errors
+error: implicitly performing saturating subtraction
+  --> tests/ui/implicit_saturating_sub.rs:371:5
+   |
+LL | /     if x != 0 {
+LL | |
+LL | |         x -= 1;
+LL | |     }
+   | |_____^ help: try: `x = x.saturating_sub(1);`
+
+error: implicitly performing saturating subtraction
+  --> tests/ui/implicit_saturating_sub.rs:380:5
+   |
+LL | /     if x != 0 {
+LL | |
+LL | |         x -= 1;
+LL | |     }
+   | |_____^ help: try: `x = x.saturating_sub(1);`
+
+error: aborting due to 31 previous errors