Rollup merge of #120183 - Zalathar:test-closure, r=compiler-errors

Add `#[coverage(off)]` to closures introduced by `#[test]` and `#[bench]`

These closures are an internal implementation detail of the `#[test]` and `#[bench]` attribute macros, so from a user perspective there is no reason to instrument them for coverage.

Skipping them makes coverage reports slightly cleaner, and will also allow other changes to span processing during coverage instrumentation, without having to worry about how they affect the `#[test]` macro.

The `#[coverage(off)]` attribute has no effect when `-Cinstrument-coverage` is not used.

Fixes #120046.

---

Note that this PR has no effect on the user-written function that has the `#[test]` attribute attached to it. That function will still be instrumented as normal.

9 files changed, 52 insertions, 18 deletions

diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index f60b73fbe9b..3e9b06a5b05 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -6,6 +6,7 @@
 #![doc(rust_logo)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(array_windows)]
+#![feature(assert_matches)]
 #![feature(box_patterns)]
 #![feature(decl_macro)]
 #![feature(if_let_guard)]
diff --git a/compiler/rustc_builtin_macros/src/test.rs b/compiler/rustc_builtin_macros/src/test.rs
index 4d44e340ae1..0631f796894 100644
--- a/compiler/rustc_builtin_macros/src/test.rs
+++ b/compiler/rustc_builtin_macros/src/test.rs
@@ -9,6 +9,7 @@ use rustc_errors::{Applicability, DiagnosticBuilder, Level};
 use rustc_expand::base::*;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::{ErrorGuaranteed, FileNameDisplayPreference, Span};
+use std::assert_matches::assert_matches;
 use std::iter;
 use thin_vec::{thin_vec, ThinVec};
 
@@ -182,6 +183,16 @@ pub fn expand_test_or_bench(
     // creates $name: $expr
     let field = |name, expr| cx.field_imm(sp, Ident::from_str_and_span(name, sp), expr);
 
+    // Adds `#[coverage(off)]` to a closure, so it won't be instrumented in
+    // `-Cinstrument-coverage` builds.
+    // This requires `#[allow_internal_unstable(coverage_attribute)]` on the
+    // corresponding macro declaration in `core::macros`.
+    let coverage_off = |mut expr: P<ast::Expr>| {
+        assert_matches!(expr.kind, ast::ExprKind::Closure(_));
+        expr.attrs.push(cx.attr_nested_word(sym::coverage, sym::off, sp));
+        expr
+    };
+
     let test_fn = if is_bench {
         // A simple ident for a lambda
         let b = Ident::from_str_and_span("b", attr_sp);
@@ -190,8 +201,9 @@ pub fn expand_test_or_bench(
             sp,
             cx.expr_path(test_path("StaticBenchFn")),
             thin_vec![
+                // #[coverage(off)]
                 // |b| self::test::assert_test_result(
-                cx.lambda1(
+                coverage_off(cx.lambda1(
                     sp,
                     cx.expr_call(
                         sp,
@@ -206,7 +218,7 @@ pub fn expand_test_or_bench(
                         ],
                     ),
                     b,
-                ), // )
+                )), // )
             ],
         )
     } else {
@@ -214,8 +226,9 @@ pub fn expand_test_or_bench(
             sp,
             cx.expr_path(test_path("StaticTestFn")),
             thin_vec![
+                // #[coverage(off)]
                 // || {
-                cx.lambda0(
+                coverage_off(cx.lambda0(
                     sp,
                     // test::assert_test_result(
                     cx.expr_call(
@@ -230,7 +243,7 @@ pub fn expand_test_or_bench(
                             ), // )
                         ],
                     ), // }
-                ), // )
+                )), // )
             ],
         )
     };
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index a2437feeeb9..9bbaf62a5ca 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -1596,7 +1596,7 @@ pub(crate) mod builtin {
     ///
     /// [the reference]: ../../../reference/attributes/testing.html#the-test-attribute
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[allow_internal_unstable(test, rustc_attrs)]
+    #[allow_internal_unstable(test, rustc_attrs, coverage_attribute)]
     #[rustc_builtin_macro]
     pub macro test($item:item) {
         /* compiler built-in */
@@ -1609,7 +1609,7 @@ pub(crate) mod builtin {
         soft,
         reason = "`bench` is a part of custom test frameworks which are unstable"
     )]
-    #[allow_internal_unstable(test, rustc_attrs)]
+    #[allow_internal_unstable(test, rustc_attrs, coverage_attribute)]
     #[rustc_builtin_macro]
     pub macro bench($item:item) {
         /* compiler built-in */
diff --git a/tests/coverage/bench.cov-map b/tests/coverage/bench.cov-map
new file mode 100644
index 00000000000..aa702a48681
--- /dev/null
+++ b/tests/coverage/bench.cov-map
@@ -0,0 +1,8 @@
+Function name: bench::my_bench
+Raw bytes (9): 0x[01, 01, 00, 01, 01, 08, 01, 00, 27]
+Number of files: 1
+- file 0 => global file 1
+Number of expressions: 0
+Number of file 0 mappings: 1
+- Code(Counter(0)) at (prev + 8, 1) to (start + 0, 39)
+
diff --git a/tests/coverage/bench.coverage b/tests/coverage/bench.coverage
new file mode 100644
index 00000000000..64945dc6415
--- /dev/null
+++ b/tests/coverage/bench.coverage
@@ -0,0 +1,9 @@
+   LL|       |#![feature(test)]
+   LL|       |// edition: 2021
+   LL|       |// compile-flags: --test
+   LL|       |
+   LL|       |extern crate test;
+   LL|       |
+   LL|       |#[bench]
+   LL|      1|fn my_bench(_b: &mut test::Bencher) {}
+
diff --git a/tests/coverage/bench.rs b/tests/coverage/bench.rs
new file mode 100644
index 00000000000..2dcd7355b2f
--- /dev/null
+++ b/tests/coverage/bench.rs
@@ -0,0 +1,8 @@
+#![feature(test)]
+// edition: 2021
+// compile-flags: --test
+
+extern crate test;
+
+#[bench]
+fn my_bench(_b: &mut test::Bencher) {}
diff --git a/tests/coverage/test_harness.cov-map b/tests/coverage/test_harness.cov-map
index 6940d2e2824..f75328b11c9 100644
--- a/tests/coverage/test_harness.cov-map
+++ b/tests/coverage/test_harness.cov-map
@@ -6,14 +6,6 @@ Number of expressions: 0
 Number of file 0 mappings: 1
 - Code(Counter(0)) at (prev + 10, 1) to (start + 0, 16)
 
-Function name: test_harness::my_test::{closure#0}
-Raw bytes (9): 0x[01, 01, 00, 01, 01, 09, 01, 00, 08]
-Number of files: 1
-- file 0 => global file 1
-Number of expressions: 0
-Number of file 0 mappings: 1
-- Code(Counter(0)) at (prev + 9, 1) to (start + 0, 8)
-
 Function name: test_harness::unused (unused)
 Raw bytes (9): 0x[01, 01, 00, 01, 00, 07, 01, 00, 0f]
 Number of files: 1
diff --git a/tests/coverage/test_harness.coverage b/tests/coverage/test_harness.coverage
index ff6009f6fce..c3f660506fb 100644
--- a/tests/coverage/test_harness.coverage
+++ b/tests/coverage/test_harness.coverage
@@ -6,6 +6,6 @@
    LL|       |#[allow(dead_code)]
    LL|      0|fn unused() {}
    LL|       |
-   LL|      1|#[test]
+   LL|       |#[test]
    LL|      1|fn my_test() {}
 
diff --git a/tests/pretty/tests-are-sorted.pp b/tests/pretty/tests-are-sorted.pp
index fd9386be8f3..fbdad0c323f 100644
--- a/tests/pretty/tests-are-sorted.pp
+++ b/tests/pretty/tests-are-sorted.pp
@@ -28,7 +28,8 @@ pub const m_test: test::TestDescAndFn =
             should_panic: test::ShouldPanic::No,
             test_type: test::TestType::Unknown,
         },
-        testfn: test::StaticTestFn(|| test::assert_test_result(m_test())),
+        testfn: test::StaticTestFn(#[coverage(off)] ||
+                test::assert_test_result(m_test())),
     };
 fn m_test() {}
 
@@ -51,7 +52,8 @@ pub const z_test: test::TestDescAndFn =
             should_panic: test::ShouldPanic::No,
             test_type: test::TestType::Unknown,
         },
-        testfn: test::StaticTestFn(|| test::assert_test_result(z_test())),
+        testfn: test::StaticTestFn(#[coverage(off)] ||
+                test::assert_test_result(z_test())),
     };
 #[ignore = "not yet implemented"]
 fn z_test() {}
@@ -75,7 +77,8 @@ pub const a_test: test::TestDescAndFn =
             should_panic: test::ShouldPanic::No,
             test_type: test::TestType::Unknown,
         },
-        testfn: test::StaticTestFn(|| test::assert_test_result(a_test())),
+        testfn: test::StaticTestFn(#[coverage(off)] ||
+                test::assert_test_result(a_test())),
     };
 fn a_test() {}
 #[rustc_main]