Lint only on single element overlap

Author: estebank

src/librustc_mir/hair/pattern/_match.rs

@@ -1077,35 +1077,20 @@ impl<'tcx> IntRange<'tcx> {
     }
 
     fn suspicious_intersection(&self, other: &Self) -> bool {
-        let (lo, hi) = (*self.range.start(), *self.range.end());
-        let (other_lo, other_hi) = (*other.range.start(), *other.range.end());
-
         // `false` in the following cases:
-        // 1     ----
-        // 2  ----------
-        //
-        // 1  ----------
-        // 2     ----
+        // 1     ----      // 1  ----------   // 1 ----        // 1       ----
+        // 2  ----------   // 2     ----      // 2       ----  // 2 ----
         //
-        // 1 ----
-        // 2       ----
+        // The following are currently `false`, but could be `true` in the future (#64007):
+        // 1 ---------       // 1     ---------
+        // 2     ----------  // 2 ----------
         //
-        // 1       ----
-        // 2 ----
-
         // `true` in the following cases:
-        // 1 ---------
-        // 2     ----------
-        lo < other_lo && hi > other_lo && hi < other_hi ||
-            // 1     ---------
-            // 2  ----------
-            lo > other_lo && lo < other_hi && hi > other_hi ||
-            // 1  ----
-            // 2     ----
-            lo == other_hi && other_lo < lo ||
-            // 1     ----
-            // 2 -----
-            hi == other_lo && lo < other_lo
+        // 1 -------          // 1       -------
+        // 2       --------   // 2 -------
+        let (lo, hi) = (*self.range.start(), *self.range.end());
+        let (other_lo, other_hi) = (*other.range.start(), *other.range.end());
+        (lo == other_hi || hi == other_lo)
     }
 }
 

src/test/ui/exhaustive_integer_patterns.rs

@@ -19,7 +19,7 @@ fn main() {
         0 ..= 32 => {}
         33 => {}
         34 .. 128 => {}
-        100 ..= 200 => {} //~ ERROR multiple patterns covering the same range
+        100 ..= 200 => {}
         200 => {} //~ ERROR unreachable pattern
         201 ..= 255 => {}
     }

src/test/ui/exhaustive_integer_patterns.stderr

@@ -1,17 +1,3 @@
-error: multiple patterns covering the same range
-  --> $DIR/exhaustive_integer_patterns.rs:22:9
-   |
-LL |         34 .. 128 => {}
-   |         --------- this range overlaps on `100u8..=127u8`
-LL |         100 ..= 200 => {}
-   |         ^^^^^^^^^^^ overlapping patterns
-   |
-note: lint level defined here
-  --> $DIR/exhaustive_integer_patterns.rs:4:9
-   |
-LL | #![deny(overlapping_patterns)]
-   |         ^^^^^^^^^^^^^^^^^^^^
-
 error: unreachable pattern
   --> $DIR/exhaustive_integer_patterns.rs:23:9
    |
@@ -101,6 +87,12 @@ LL |         0 .. 2 => {}
    |         ------ this range overlaps on `1u8`
 LL |         1 ..= 2 => {}
    |         ^^^^^^^ overlapping patterns
+   |
+note: lint level defined here
+  --> $DIR/exhaustive_integer_patterns.rs:4:9
+   |
+LL | #![deny(overlapping_patterns)]
+   |         ^^^^^^^^^^^^^^^^^^^^
 
 error[E0004]: non-exhaustive patterns: `std::u128::MAX` not covered
   --> $DIR/exhaustive_integer_patterns.rs:146:11
@@ -126,6 +118,6 @@ LL |     match 0u128 {
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
-error: aborting due to 15 previous errors
+error: aborting due to 14 previous errors
 
 For more information about this error, try `rustc --explain E0004`.

src/test/ui/issues/issue-13867.rs

@@ -1,8 +1,6 @@
 // run-pass
 // Test that codegen works correctly when there are multiple refutable
 // patterns in match expression.
-#![allow(overlapping_patterns)]
-
 
 enum Foo {
     FooUint(usize),

src/test/ui/precise_pointer_size_matching.rs

@@ -28,6 +28,6 @@ fn main() {
 
     match 0usize { //~ ERROR non-exhaustive patterns
         1 ..= 8 => {}
-        5 ..= 20 => {} //~ ERROR multiple patterns covering the same range
+        5 ..= 20 => {}
     }
 }

src/test/ui/precise_pointer_size_matching.stderr

@@ -6,20 +6,6 @@ LL |     match 0isize {
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
-error: multiple patterns covering the same range
-  --> $DIR/precise_pointer_size_matching.rs:31:9
-   |
-LL |         1 ..= 8 => {}
-   |         ------- this range overlaps on `5usize..=8usize`
-LL |         5 ..= 20 => {}
-   |         ^^^^^^^^ overlapping patterns
-   |
-note: lint level defined here
-  --> $DIR/precise_pointer_size_matching.rs:11:31
-   |
-LL | #![deny(unreachable_patterns, overlapping_patterns)]
-   |                               ^^^^^^^^^^^^^^^^^^^^
-
 error[E0004]: non-exhaustive patterns: `0usize` and `21usize..=std::usize::MAX` not covered
   --> $DIR/precise_pointer_size_matching.rs:29:11
    |
@@ -28,6 +14,6 @@ LL |     match 0usize {
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0004`.