Add some reasons why tests are ignored.

tests/mir-opt/simplify_arm.rs

@@ -6,8 +6,7 @@
 // EMIT_MIR simplify_arm.id_try.SimplifyArmIdentity.diff
 // EMIT_MIR simplify_arm.id_try.SimplifyBranchSame.diff
 
-// This pass is broken since deaggregation changed
-// ignore-test
+// ignore-test This pass is broken since deaggregation changed
 
 fn id(o: Option<u8>) -> Option<u8> {
     match o {

tests/mir-opt/simplify_arm_identity.rs

@@ -4,8 +4,7 @@
 // compile-flags: -Zmir-opt-level=3
 // EMIT_MIR_FOR_EACH_BIT_WIDTH
 
-// This pass is broken since deaggregation changed
-// ignore-test
+// ignore-test This pass is broken since deaggregation changed
 
 enum Src {
     Foo(u8),

tests/ui/borrowck/move-error-snippets-ext.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 macro_rules! aaa {
     ($c:ident) => {{

tests/ui/codemap_tests/two_files_data.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 trait Foo { }
 

tests/ui/conditional-compilation/module_with_cfg.rs

@@ -1,3 +1,3 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 #![cfg_attr(all(), cfg(FALSE))]

tests/ui/cross/cross-file-errors/main.stderr

@@ -1,5 +1,5 @@
 error: in expressions, `_` can only be used on the left-hand side of an assignment
-  --> $DIR/underscore.rs:8:9
+  --> $DIR/underscore.rs:6:9
    |
 LL |         _
    |         ^ `_` not allowed here

tests/ui/cross/cross-file-errors/underscore.rs

@@ -1,6 +1,4 @@
-// We want this file only so we can test cross-file error
-// messages, but we don't want it in an external crate.
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 #![crate_type = "lib"]
 
 macro_rules! underscore {

tests/ui/inline-const/const-match-pat-lifetime-err.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (This is currently broken)
 
 #![allow(incomplete_features)]
 #![feature(const_mut_refs)]

tests/ui/issues/issue-49298.rs

@@ -6,7 +6,7 @@
 // where #54986 is implemented and #54987 is *not* implemented. For
 // now: just ignore it
 //
-// ignore-test
+// ignore-test (#54987)
 
 // This test is checking that the space allocated for `x.1` does not
 // overlap with `y`. (The reason why such a thing happened at one

tests/ui/issues/issue-59756.rs

@@ -1,5 +1,5 @@
 // run-rustfix
-// ignore-test
+// ignore-test (rustfix needs multiple suggestions)
 //
 // FIXME: Re-enable this test once we support choosing
 // between multiple mutually exclusive suggestions for the same span

tests/ui/macros/macro-expanded-include/foo/mod.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 macro_rules! m {
     () => { include!("file.txt"); }

tests/ui/match/issue-26996.rs

@@ -4,7 +4,7 @@
 // where #54986 is implemented and #54987 is *not* implemented. For
 // now: just ignore it
 //
-// ignore-test
+// ignore-test (#54987)
 
 // This test is checking that the write to `c.0` (which has been moved out of)
 // won't overwrite the state in `c2`.

tests/ui/match/issue-27021.rs

@@ -4,7 +4,7 @@
 // where #54986 is implemented and #54987 is *not* implemented. For
 // now: just ignore it
 //
-// ignore-test
+// ignore-test (#54987)
 
 // These are variants of issue-26996.rs. In all cases we are writing
 // into a record field that has been moved out of, and ensuring that

tests/ui/numbers-arithmetic/saturating-float-casts-impl.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 // Tests saturating float->int casts. See u128-as-f32.rs for the opposite direction.
 //

tests/ui/panics/panic-short-backtrace-windows-x86_64.rs

@@ -1,6 +1,6 @@
 // This test has been spuriously failing a lot recently (#92000).
 // Ignore it until the underlying issue is fixed.
-// ignore-test
+// ignore-test (#92000)
 
 // Regression test for #87481: short backtrace formatting cut off the entire stack trace.
 

tests/ui/proc-macro/module.rs

@@ -1 +1 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)

tests/ui/proc-macro/module_with_attrs.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 #![rustfmt::skip]
 #![print_attr]

tests/ui/proc-macro/outer/inner.rs

@@ -1 +1 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)

tests/ui/proc-macro/pretty-print-hack/allsorts-rental-0.5.6/src/lib.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 #[derive(Print)]
 enum ProceduralMasqueradeDummyType {

tests/ui/proc-macro/pretty-print-hack/rental-0.5.5/src/lib.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 #[derive(Print)]
 enum ProceduralMasqueradeDummyType {

tests/ui/proc-macro/pretty-print-hack/rental-0.5.6/src/lib.rs

@@ -1,4 +1,4 @@
-// ignore-test
+// ignore-test (auxiliary, used by other tests)
 
 #[derive(Print)]
 enum ProceduralMasqueradeDummyType {