Unnecessary call to min/max method #12368

vohoanglong0107 · 2024-02-28T04:41:53Z

Continuation of #12061
Fix #11901 and #11924

This implementation only deal with literal int, like i32::MAX, -6_i32, 0

changelog: added lint [unnecessary_min_max]

rustbot · 2024-02-28T04:41:58Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Alexendoo (or someone else) some time within the next two weeks.

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bors · 2024-03-22T13:36:16Z

☔ The latest upstream changes (presumably #12508) made this pull request unmergeable. Please resolve the merge conflicts.

Alexendoo · 2024-03-22T14:15:13Z

clippy_lints/src/methods/unnecessary_min_max.rs

+    match (ty.kind(), cv) {
+        (&ty::Uint(_), Constant::Int(0)) => Some(Extrema::Minimum),
+        (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::MIN >> (128 - int_bits(cx.tcx, ity)), ity) => {
+            Some(Extrema::Minimum)
+        },
+
+        (&ty::Int(ity), Constant::Int(i)) if i == unsext(cx.tcx, i128::MAX >> (128 - int_bits(cx.tcx, ity)), ity) => {
+            Some(Extrema::Maximum)
+        },
+        (&ty::Uint(uty), Constant::Int(i)) if i == clip(cx.tcx, u128::MAX, uty) => Some(Extrema::Maximum),
+
+        _ => None,
+    }


unsext/clip/int_bits handle usize/isize but for this lint we wouldn't want that (excluding 0usize) to ensure x.min(i32::MAX as isize) doesn't lint on 32 bit targets

cv.int_value(...)? could replace the unsexts with ity/uty.bit_width() instead of int_bits to exclude *size

ensure x.min(i32::MAX as isize) doesn't lint on 32 bit targets

I don't really understand this. If x is of i32, it shouldn't be able to be compared to i32::MAX as isize?

In that example it would be that x is an isize, it wasn't a reference to the existing i32 x in the test file

tests/ui/cast.stderr

Alexendoo · 2024-03-26T18:02:06Z

tests/ui/unnecessary_min_max.fixed

+        min = min.min(random_u32());
+    }
+
+    let _ = (u32::MIN as isize).min(42);


An implementation detail of constant but I don't think it handles as casts, you'd need to either put these in a const or inline the value as e.g. 2147483647isize with a comment

Alexendoo · 2024-03-27T13:55:56Z

clippy_lints/src/methods/unnecessary_min_max.rs

+}
+
+fn lint(cx: &LateContext<'_>, expr: &Expr<'_>, name: &str, lhs: Span, rhs: Span, order: Ordering) {
+    let cmp_str = if (name == "min" && order.is_ge()) || (name == "max" && order.is_ge()) {


I believe this can be

Suggested change

let cmp_str = if (name == "min" && order.is_ge()) || (name == "max" && order.is_ge()) {

let cmp_str = if order.is_ge() {

With that & squashed commits I think we're good to go

Alexendoo · 2024-03-30T15:37:34Z

zulip thread: https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/FCP.20.60unnecessary_min_max.60

bors · 2024-04-04T23:51:58Z

☔ The latest upstream changes (presumably #12631) made this pull request unmergeable. Please resolve the merge conflicts.

Alexendoo · 2024-04-23T14:46:31Z

clippy_lints/src/methods/unnecessary_min_or_max.rs

+fn is_external_const(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
+    let ExprKind::Path(ref qpath) = expr.kind else {
+        return false;
+    };
+
+    let Some(def_id) = cx.qpath_res(qpath, expr.hir_id()).opt_def_id() else {
+        return false;
+    };
+    !def_id.is_local()
+}


This won't catch some indirect usage, e.g. EXTERNAL_CONST + 1. You can use constant_with_source but it doesn't currently track if the constant is local or not. That's probably fine though as the same logic of it may only happen to be 0 applies to local constants equally

A good addition would be to have the const evaluation distinguish consts in core, it would be a shame to lose those

I agree. A significant purpose of this lint rule is to detect incorrect usage of i32::MIN. I will see what I can do here.

Alexendoo · 2024-04-28T12:55:20Z

clippy_utils/src/consts.rs

+    /// Simple constant folding to determine if an expression depends on an external crate
+    /// excluding crates listed in exceptions
+    pub fn expr_is_external(&mut self, e: &Expr<'_>, exceptions: &[Symbol]) -> bool {


Let's add a new variant and check it in expr/fetch_path_and_apply rather than revisiting after the fact. It can be just specific to core as that's all we're using it for currently. ConstantSource::CoreConstant or similar

bors · 2024-05-03T09:34:34Z

☔ The latest upstream changes (presumably #12567) made this pull request unmergeable. Please resolve the merge conflicts.

Alexendoo · 2024-05-06T12:08:59Z

clippy_utils/src/consts.rs

+    /// The value is dependent on a constant defined in current crate of `core` crate.
+    LocalOrCoreCrateConstant,


Let's keep it just core constants, local ones may have "arbitrary" values just as remote ones do while the ones in core are pretty straight forward

Alexendoo · 2024-05-06T12:10:28Z

clippy_config/src/conf.rs

+    /// Lint: UNNECESSARY_MIN_OR_MAX.
+    ///
+    /// Whether to also run the lints on external defined consts.
+    (allowed_external_crates: bool = false),


I think it would be fine to have no config, it seems like it would be very rare that an external crate would redefine a constant to be MIN/MAX in a way that the user wants to trigger the lint

bors · 2024-06-03T09:14:41Z

☔ The latest upstream changes (presumably #12815) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot · 2024-06-03T09:43:13Z

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git pull --rebase https://github.com/rust-lang/rust-clippy.git master
$ git push --force-with-lease

The following commits are merge commits:

aa83de2

Alexendoo

Sorry I forgot to press submit review and left this as pending 😅

Alexendoo · 2024-05-17T13:35:03Z

clippy_utils/src/consts.rs

+                    this.source = if is_core_crate {
+                        ConstantSource::CoreConstant
+                    } else {
+                        ConstantSource::Constant
+                    };


If source is already Constant we wouldn't want to override it with CoreConstant

Sorry for taking so long to come back to this 🙇 I have pushed the new changes, could you give it another go?

bors · 2024-06-16T23:06:15Z

☔ The latest upstream changes (presumably #12287) made this pull request unmergeable. Please resolve the merge conflicts.

Alexendoo · 2024-06-20T13:22:12Z

clippy_lints/src/methods/unnecessary_min_or_max.rs

+    if let (
+        Some((left, ConstantSource::Local | ConstantSource::CoreConstant)),
+        Some((right, ConstantSource::Local | ConstantSource::CoreConstant)),
+    ) = (
+        constant_with_source(cx, typeck_results, recv),
+        constant_with_source(cx, typeck_results, arg),
+    ) {


Let's go with if let Some(..) == constant_with_source(..) && let Some(..) = constant_with_source(..) so we don't have to evaluate arg as a constant if recv isn't one

Alexendoo · 2024-06-20T14:11:49Z

Great, thanks!

@bors r+

bors · 2024-06-20T14:11:52Z

📌 Commit 2f9f204 has been approved by Alexendoo

It is now in the queue for this repository.

bors · 2024-06-20T14:12:59Z

⌛ Testing commit 2f9f204 with merge 3e84ca8...

bors · 2024-06-20T14:22:03Z

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: Alexendoo
Pushing 3e84ca8 to master...

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Alexendoo added S-final-comment-period Status: final comment period it will be merged unless new objections are raised (~1 week) and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties labels Mar 30, 2024

xFrednet mentioned this pull request Apr 1, 2024

implemented unnecessary min #12061

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rustbot added has-merge-commits PR has merge commits, merge with caution. S-waiting-on-author Status: This is awaiting some action from the author. (Use `@rustbot ready` to update this status) labels Jun 3, 2024

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feat: unnecessary_min_max lint

2f9f204

vohoanglong0107 force-pushed the unnecessary-min branch from e9501b8 to 2f9f204 Compare June 20, 2024 13:57

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bors merged commit 3e84ca8 into rust-lang:master Jun 20, 2024
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y21 mentioned this pull request Sep 11, 2024

unnecessary call to min function #11924

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Unnecessary call to min/max method #12368

Unnecessary call to min/max method #12368

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	let cmp_str = if (name == "min" && order.is_ge()) \|\| (name == "max" && order.is_ge()) {
	let cmp_str = if order.is_ge() {

		/// The value is dependent on a constant defined in current crate of `core` crate.
		LocalOrCoreCrateConstant,

Unnecessary call to min/max method #12368

Unnecessary call to min/max method #12368

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