check for overlapping ranges

clippy_lints/src/manual_range_pattern.rs

@@ -2,8 +2,10 @@ use clippy_utils::diagnostics::span_lint_and_sugg;
 use rustc_ast::LitKind;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Applicability;
+use rustc_hir::Expr;
 use rustc_hir::ExprKind;
 use rustc_hir::PatKind;
+use rustc_hir::RangeEnd;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
@@ -32,6 +34,16 @@ declare_clippy_lint! {
 }
 declare_lint_pass!(ManualRangePattern => [MANUAL_RANGE_PATTERN]);
 
+fn expr_as_u128(expr: &Expr<'_>) -> Option<u128> {
+    if let ExprKind::Lit(lit) = expr.kind
+        && let LitKind::Int(num, _) = lit.node
+    {
+        Some(num)
+    } else {
+        None
+    }
+}
+
 impl LateLintPass<'_> for ManualRangePattern {
     fn check_pat(&mut self, cx: &LateContext<'_>, pat: &'_ rustc_hir::Pat<'_>) {
         if pat.span.from_expansion() {
@@ -42,25 +54,55 @@ impl LateLintPass<'_> for ManualRangePattern {
             let mut min = u128::MAX;
             let mut max = 0;
             let mut numbers_found = FxHashSet::default();
+            let mut ranges_found = Vec::new();
 
             for pat in pats {
                 if let PatKind::Lit(lit) = pat.kind
-                    && let ExprKind::Lit(lit) = lit.kind
-                    && let LitKind::Int(num, _) = lit.node
+                    && let Some(num) = expr_as_u128(lit)
                 {
                     numbers_found.insert(num);
 
                     min = min.min(num);
                     max = max.max(num);
+                } else if let PatKind::Range(Some(left), Some(right), end) = pat.kind
+                    && let Some(left) = expr_as_u128(left)
+                    && let Some(right) = expr_as_u128(right)
+                    && right >= left
+                {
+                    min = min.min(left);
+                    max = max.max(right);
+                    ranges_found.push(left..=match end {
+                        RangeEnd::Included => right,
+                        RangeEnd::Excluded => right - 1,
+                    });
                 } else {
                     return;
                 }
             }
 
             // a pattern like 1 | 2 seems fine, lint if there are at least 3 alternatives
-            if numbers_found.len() >= 3 {
-                let contains_whole_range = (max - min == numbers_found.len() as u128 - 1)
-                    && (min..=max).all(|num| numbers_found.contains(&num));
+            if pats.len() >= 3 {
+                let contains_whole_range = 'contains: {
+                    let mut num = min;
+                    while num <= max {
+                        if numbers_found.contains(&num) {
+                            num += 1;
+                        }
+                        // Given a list of (potentially overlapping) ranges like:
+                        // 1..=5, 3..=7, 6..=10
+                        // We want to find the range with the highest end that still contains the current number
+                        else if let Some(range) = ranges_found
+                            .iter()
+                            .filter(|range| range.contains(&num))
+                            .max_by_key(|range| range.end())
+                        {
+                            num = range.end() + 1;
+                        } else {
+                            break 'contains false;
+                        }
+                    }
+                    break 'contains true;
+                };
 
                 if contains_whole_range {
                     span_lint_and_sugg(

tests/ui/manual_range_pattern.fixed

@@ -2,6 +2,7 @@
 
 #![allow(unused)]
 #![warn(clippy::manual_range_pattern)]
+#![feature(exclusive_range_pattern)]
 
 fn main() {
     let f = 6;
@@ -14,6 +15,11 @@ fn main() {
     let _ = matches!(f, 1 | 2147483647);
     let _ = matches!(f, 0 | 2147483647);
     let _ = matches!(f, -2147483647 | 2147483647);
+    let _ = matches!(f, 1 | (2..=4));
+    let _ = matches!(f, 1 | (2..4));
+    let _ = matches!(f, 1..=48324729);
+    let _ = matches!(f, 0..=48324730);
+    let _ = matches!(f, 0..=3);
     #[allow(clippy::match_like_matches_macro)]
     let _ = match f {
         1..=10 => true,

tests/ui/manual_range_pattern.rs

@@ -2,6 +2,7 @@
 
 #![allow(unused)]
 #![warn(clippy::manual_range_pattern)]
+#![feature(exclusive_range_pattern)]
 
 fn main() {
     let f = 6;
@@ -14,6 +15,11 @@ fn main() {
     let _ = matches!(f, 1 | 2147483647);
     let _ = matches!(f, 0 | 2147483647);
     let _ = matches!(f, -2147483647 | 2147483647);
+    let _ = matches!(f, 1 | (2..=4));
+    let _ = matches!(f, 1 | (2..4));
+    let _ = matches!(f, (1..=10) | (2..=13) | (14..=48324728) | 48324729);
+    let _ = matches!(f, 0 | (1..=10) | 48324730 | (2..=13) | (14..=48324728) | 48324729);
+    let _ = matches!(f, 0..=1 | 0..=2 | 0..=3);
     #[allow(clippy::match_like_matches_macro)]
     let _ = match f {
         1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,

tests/ui/manual_range_pattern.stderr

@@ -1,22 +1,40 @@
 error: this OR pattern can be rewritten using a range
-  --> $DIR/manual_range_pattern.rs:9:25
+  --> $DIR/manual_range_pattern.rs:10:25
    |
 LL |     let _ = matches!(f, 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10);
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `1..=10`
    |
    = note: `-D clippy::manual-range-pattern` implied by `-D warnings`
 
 error: this OR pattern can be rewritten using a range
-  --> $DIR/manual_range_pattern.rs:10:25
+  --> $DIR/manual_range_pattern.rs:11:25
    |
 LL |     let _ = matches!(f, 4 | 2 | 3 | 1 | 5 | 6 | 9 | 7 | 8 | 10);
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `1..=10`
 
 error: this OR pattern can be rewritten using a range
-  --> $DIR/manual_range_pattern.rs:19:9
+  --> $DIR/manual_range_pattern.rs:20:25
+   |
+LL |     let _ = matches!(f, (1..=10) | (2..=13) | (14..=48324728) | 48324729);
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `1..=48324729`
+
+error: this OR pattern can be rewritten using a range
+  --> $DIR/manual_range_pattern.rs:21:25
+   |
+LL |     let _ = matches!(f, 0 | (1..=10) | 48324730 | (2..=13) | (14..=48324728) | 48324729);
+   |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `0..=48324730`
+
+error: this OR pattern can be rewritten using a range
+  --> $DIR/manual_range_pattern.rs:22:25
+   |
+LL |     let _ = matches!(f, 0..=1 | 0..=2 | 0..=3);
+   |                         ^^^^^^^^^^^^^^^^^^^^^ help: try: `0..=3`
+
+error: this OR pattern can be rewritten using a range
+  --> $DIR/manual_range_pattern.rs:25:9
    |
 LL |         1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 => true,
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `1..=10`
 
-error: aborting due to 3 previous errors
+error: aborting due to 6 previous errors