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Rollup merge of rust-lang#120185 - Zalathar:auto-derived, r=wesleywiser
coverage: Don't instrument `#[automatically_derived]` functions This PR makes the coverage instrumentor detect and skip functions that have [`#[automatically_derived]`](https://doc.rust-lang.org/reference/attributes/derive.html#the-automatically_derived-attribute) on their enclosing impl block. Most notably, this means that methods generated by built-in derives (e.g. `Clone`, `Debug`, `PartialEq`) are now ignored by coverage instrumentation, and won't appear as executed or not-executed in coverage reports. This is a noticeable change in user-visible behaviour, but overall I think it's a net improvement. For example, we've had a few user requests for this sort of change (e.g. rust-lang#105055, rust-lang#84605 (comment)), and I believe it's the behaviour that most users will expect/prefer by default. It's possible to imagine situations where users would want to instrument these derived implementations, but I think it's OK to treat that as an opportunity to consider adding more fine-grained option flags to control the details of coverage instrumentation, while leaving this new behaviour as the default. (Also note that while `-Cinstrument-coverage` is a stable feature, the exact details of coverage instrumentation are allowed to change. So we *can* make this change; the main question is whether we *should*.) Fixes rust-lang#105055.
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‎compiler/rustc_mir_transform/src/coverage/mod.rs

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@@ -384,7 +384,18 @@ fn is_eligible_for_coverage(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
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return false;
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}
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// Don't instrument functions with `#[automatically_derived]` on their
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// enclosing impl block, on the assumption that most users won't care about
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// coverage for derived impls.
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if let Some(impl_of) = tcx.impl_of_method(def_id.to_def_id())
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&& tcx.is_automatically_derived(impl_of)
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{
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trace!("InstrumentCoverage skipped for {def_id:?} (automatically derived)");
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return false;
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}
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if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::NO_COVERAGE) {
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trace!("InstrumentCoverage skipped for {def_id:?} (`#[coverage(off)]`)");
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return false;
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}
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‎tests/coverage-run-rustdoc/doctest.coverage

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@@ -34,8 +34,7 @@ $DIR/doctest.rs:
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LL| |//!
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LL| |//! doctest returning a result:
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LL| 1|//! ```
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LL| 2|//! #[derive(Debug, PartialEq)]
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^1
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LL| 1|//! #[derive(Debug, PartialEq)]
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LL| 1|//! struct SomeError {
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LL| 1|//! msg: String,
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LL| 1|//! }
@@ -63,7 +62,7 @@ $DIR/doctest.rs:
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LL| 1|//! println!("called some_func()");
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LL| 1|//! }
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LL| |//!
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LL| 0|//! #[derive(Debug)]
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LL| |//! #[derive(Debug)]
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LL| |//! struct SomeError;
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LL| |//!
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LL| |//! extern crate doctest_crate;

‎tests/coverage/bad_counter_ids.cov-map

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@@ -1,19 +1,3 @@
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Function name: <bad_counter_ids::Foo as core::cmp::PartialEq>::eq
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 0c, 11, 00, 1a]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Counter(0)) at (prev + 12, 17) to (start + 0, 26)
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Function name: <bad_counter_ids::Foo as core::fmt::Debug>::fmt
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 0c, 0a, 00, 0f]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Counter(0)) at (prev + 12, 10) to (start + 0, 15)
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Function name: bad_counter_ids::eq_bad
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Raw bytes (14): 0x[01, 01, 00, 02, 01, 23, 01, 02, 1f, 00, 03, 01, 00, 02]
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Number of files: 1

‎tests/coverage/bad_counter_ids.coverage

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@@ -9,7 +9,7 @@
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LL| |// a too-large counter ID and silently discard the entire function from its
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LL| |// coverage reports.
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LL| |
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LL| 8|#[derive(Debug, PartialEq, Eq)]
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LL| |#[derive(Debug, PartialEq, Eq)]
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LL| |struct Foo(u32);
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LL| |
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LL| 1|fn eq_good() {

‎tests/coverage/issue-83601.cov-map

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@@ -1,19 +1,3 @@
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Function name: <issue_83601::Foo as core::cmp::PartialEq>::eq
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 03, 11, 00, 1a]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Counter(0)) at (prev + 3, 17) to (start + 0, 26)
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Function name: <issue_83601::Foo as core::fmt::Debug>::fmt
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 03, 0a, 00, 0f]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Counter(0)) at (prev + 3, 10) to (start + 0, 15)
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Function name: issue_83601::main
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Raw bytes (21): 0x[01, 01, 01, 05, 09, 03, 01, 06, 01, 02, 1c, 05, 03, 09, 01, 1c, 02, 02, 05, 03, 02]
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Number of files: 1

‎tests/coverage/issue-83601.coverage

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@@ -1,7 +1,6 @@
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LL| |// Shows that rust-lang/rust/83601 is resolved
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LL| |
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LL| 3|#[derive(Debug, PartialEq, Eq)]
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^2
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LL| |#[derive(Debug, PartialEq, Eq)]
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LL| |struct Foo(u32);
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LL| |
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LL| 1|fn main() {

‎tests/coverage/issue-84561.cov-map

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@@ -1,11 +1,3 @@
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Function name: <issue_84561::Foo as core::cmp::PartialEq>::eq
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 04, 0a, 00, 13]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Counter(0)) at (prev + 4, 10) to (start + 0, 19)
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Function name: <issue_84561::Foo as core::fmt::Debug>::fmt
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Raw bytes (29): 0x[01, 01, 02, 01, 05, 05, 02, 04, 01, 8a, 01, 05, 01, 25, 05, 01, 25, 00, 26, 02, 01, 09, 00, 0f, 07, 01, 05, 00, 06]
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Number of files: 1

‎tests/coverage/issue-84561.coverage

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LL| |// This demonstrated Issue #84561: function-like macros produce unintuitive coverage results.
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LL| |
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LL| |// failure-status: 101
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LL| 21|#[derive(PartialEq, Eq)]
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LL| |#[derive(PartialEq, Eq)]
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LL| |struct Foo(u32);
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LL| |
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LL| |#[rustfmt::skip]

‎tests/coverage/partial_eq.cov-map

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@@ -1,51 +1,3 @@
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Function name: <partial_eq::Version as core::clone::Clone>::clone (unused)
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Raw bytes (9): 0x[01, 01, 00, 01, 00, 04, 0a, 00, 0f]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Zero) at (prev + 4, 10) to (start + 0, 15)
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Function name: <partial_eq::Version as core::cmp::Ord>::cmp (unused)
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Raw bytes (14): 0x[01, 01, 00, 02, 00, 04, 33, 00, 34, 00, 00, 35, 00, 36]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 2
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- Code(Zero) at (prev + 4, 51) to (start + 0, 52)
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- Code(Zero) at (prev + 0, 53) to (start + 0, 54)
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Function name: <partial_eq::Version as core::cmp::PartialEq>::eq (unused)
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Raw bytes (14): 0x[01, 01, 00, 02, 00, 04, 18, 00, 19, 00, 00, 20, 00, 21]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 2
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- Code(Zero) at (prev + 4, 24) to (start + 0, 25)
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- Code(Zero) at (prev + 0, 32) to (start + 0, 33)
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Function name: <partial_eq::Version as core::cmp::PartialOrd>::partial_cmp
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Raw bytes (22): 0x[01, 01, 04, 07, 0b, 00, 09, 0f, 15, 00, 11, 02, 01, 04, 27, 00, 28, 03, 00, 30, 00, 31]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 4
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- expression 0 operands: lhs = Expression(1, Add), rhs = Expression(2, Add)
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- expression 1 operands: lhs = Zero, rhs = Counter(2)
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- expression 2 operands: lhs = Expression(3, Add), rhs = Counter(5)
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- expression 3 operands: lhs = Zero, rhs = Counter(4)
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Number of file 0 mappings: 2
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- Code(Counter(0)) at (prev + 4, 39) to (start + 0, 40)
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- Code(Expression(0, Add)) at (prev + 0, 48) to (start + 0, 49)
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= ((Zero + c2) + ((Zero + c4) + c5))
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Function name: <partial_eq::Version as core::fmt::Debug>::fmt
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 04, 11, 00, 16]
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Number of files: 1
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- file 0 => global file 1
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Number of expressions: 0
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Number of file 0 mappings: 1
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- Code(Counter(0)) at (prev + 4, 17) to (start + 0, 22)
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Function name: <partial_eq::Version>::new
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Raw bytes (9): 0x[01, 01, 00, 01, 01, 0c, 05, 06, 06]
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Number of files: 1

‎tests/coverage/partial_eq.coverage

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@@ -1,8 +1,7 @@
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LL| |// This test confirms an earlier problem was resolved, supporting the MIR graph generated by the
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LL| |// structure of this test.
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LL| |
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LL| 2|#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
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^0 ^0 ^0 ^1 ^1 ^0^0
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LL| |#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
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LL| |pub struct Version {
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LL| | major: usize,
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LL| | minor: usize,

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