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

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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

min_max make people think about minmax

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

rustbot assigned Alexendoo Feb 28, 2024

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties label Feb 28, 2024

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vohoanglong0107 force-pushed the unnecessary-min branch 2 times, most recently from 5d840b6 to 2a22b1c Compare March 25, 2024 01:03

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vohoanglong0107 force-pushed the unnecessary-min branch 2 times, most recently from 894ea82 to 961adc9 Compare March 27, 2024 22:47

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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

Closed

vohoanglong0107 force-pushed the unnecessary-min branch from 882f85b to 7a091b3 Compare April 4, 2024 06:00

vohoanglong0107 force-pushed the unnecessary-min branch 3 times, most recently from 5160ac7 to d7d6b41 Compare April 9, 2024 09:10

vohoanglong0107 force-pushed the unnecessary-min branch from b4b77cd to 2a688ad Compare April 23, 2024 08:58

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vohoanglong0107 force-pushed the unnecessary-min branch 2 times, most recently from fc2d35c to f446e4e Compare April 28, 2024 08:31

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vohoanglong0107 force-pushed the unnecessary-min branch from c36178e to 9d33968 Compare April 29, 2024 03:06

vohoanglong0107 added 8 commits April 29, 2024 03:32

feat: unnecessary_min_max lint

e9938be

docs: explain more clearly why it was bad

cf56d3b

fix: use more descriptive name

1492779

min_max make people think about minmax

feat: add a config option to enable lint on external crate

7452cea

fix: lint

4ed5919

fix: exclude core from external crates

e8e3722

refactor: use add core crate constant source

6cb40f1

test: external crate consts

31f5010

vohoanglong0107 force-pushed the unnecessary-min branch from 9d33968 to 31f5010 Compare April 29, 2024 03:33

vohoanglong0107 requested a review from Alexendoo April 29, 2024 03:46

Alexendoo reviewed May 6, 2024

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Unnecessary call to min/max method #12368

Unnecessary call to min/max method #12368

vohoanglong0107 commented Feb 28, 2024 •

edited

rustbot commented Feb 28, 2024

bors commented Mar 22, 2024

Alexendoo Mar 22, 2024 •

edited

vohoanglong0107 Mar 27, 2024 •

edited

Alexendoo Mar 27, 2024

Alexendoo Mar 26, 2024 •

edited

Alexendoo Mar 27, 2024

Alexendoo Mar 27, 2024

Alexendoo commented Mar 30, 2024

bors commented Apr 4, 2024

Alexendoo Apr 23, 2024

vohoanglong0107 Apr 28, 2024

Alexendoo Apr 28, 2024

bors commented May 3, 2024

Alexendoo May 6, 2024

Alexendoo May 6, 2024

	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

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Unnecessary call to min/max method #12368

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vohoanglong0107 commented Feb 28, 2024 • edited

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vohoanglong0107 commented Feb 28, 2024 •

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Alexendoo Mar 22, 2024 •

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vohoanglong0107 Mar 27, 2024 •

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Alexendoo Mar 26, 2024 •

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