Add a note to duplicate diagnostics

compiler/rustc_errors/src/lib.rs

@@ -1376,16 +1376,16 @@ impl HandlerInner {
                 self.emitted_diagnostic_codes.insert(code.clone());
             }
 
-            let already_emitted = |this: &mut Self| {
+            let already_emitted = {
                 let mut hasher = StableHasher::new();
                 diagnostic.hash(&mut hasher);
                 let diagnostic_hash = hasher.finish();
-                !this.emitted_diagnostics.insert(diagnostic_hash)
+                !self.emitted_diagnostics.insert(diagnostic_hash)
             };
 
             // Only emit the diagnostic if we've been asked to deduplicate or
             // haven't already emitted an equivalent diagnostic.
-            if !(self.flags.deduplicate_diagnostics && already_emitted(self)) {
+            if !(self.flags.deduplicate_diagnostics && already_emitted) {
                 debug!(?diagnostic);
                 debug!(?self.emitted_diagnostics);
                 let already_emitted_sub = |sub: &mut SubDiagnostic| {
@@ -1401,6 +1401,9 @@ impl HandlerInner {
                 };
 
                 diagnostic.children.extract_if(already_emitted_sub).for_each(|_| {});
+                if already_emitted {
+                    diagnostic.note("duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`");
+                }
 
                 self.emitter.emit_diagnostic(diagnostic);
                 if diagnostic.is_error() {

tests/ui/allocator/not-an-allocator.stderr

@@ -18,6 +18,7 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
@@ -29,6 +30,7 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
@@ -40,6 +42,7 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors

tests/ui/associated-consts/defaults-not-assumed-fail.stderr

@@ -24,6 +24,7 @@ note: erroneous constant encountered
 LL |     assert_eq!(<() as Tr>::B, 0);    // causes the error above
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this note originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

tests/ui/associated-inherent-types/issue-109789.stderr

@@ -15,6 +15,7 @@ LL | fn bar(_: Foo<for<'a> fn(&'a ())>::Assoc) {}
    |
    = note: expected struct `Foo<fn(&'static ())>`
               found struct `Foo<for<'a> fn(&'a ())>`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 2 previous errors
 

tests/ui/associated-type-bounds/duplicate.stderr

@@ -373,6 +373,8 @@ LL | trait TRS1: Iterator<Item: Copy, Item: Send> {}
    |                      ----------  ^^^^^^^^^^ re-bound here
    |                      |
    |                      `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
   --> $DIR/duplicate.rs:197:34
@@ -389,6 +391,8 @@ LL | trait TRS2: Iterator<Item: Copy, Item: Copy> {}
    |                      ----------  ^^^^^^^^^^ re-bound here
    |                      |
    |                      `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
   --> $DIR/duplicate.rs:200:37
@@ -405,6 +409,8 @@ LL | trait TRS3: Iterator<Item: 'static, Item: 'static> {}
    |                      -------------  ^^^^^^^^^^^^^ re-bound here
    |                      |
    |                      `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
   --> $DIR/duplicate.rs:205:29
@@ -445,6 +451,8 @@ LL |     Self: Iterator<Item: Copy, Item: Send>,
    |                    ----------  ^^^^^^^^^^ re-bound here
    |                    |
    |                    `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
   --> $DIR/duplicate.rs:230:32
@@ -461,6 +469,8 @@ LL |     Self: Iterator<Item: Copy, Item: Copy>,
    |                    ----------  ^^^^^^^^^^ re-bound here
    |                    |
    |                    `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
   --> $DIR/duplicate.rs:237:35
@@ -477,6 +487,8 @@ LL |     Self: Iterator<Item: 'static, Item: 'static>,
    |                    -------------  ^^^^^^^^^^^^^ re-bound here
    |                    |
    |                    `Item` bound here first
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0719]: the value of the associated type `Item` (from trait `Iterator`) is already specified
   --> $DIR/duplicate.rs:255:40

tests/ui/associated-types/hr-associated-type-bound-param-2.stderr

@@ -45,6 +45,7 @@ LL | trait Z<'a, T: ?Sized>
 ...
 LL |     for<'b> <T as Z<'b, u16>>::W: Clone,
    |                                   ^^^^^ required by this bound in `Z`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 3 previous errors
 

tests/ui/async-await/drop-tracking-unresolved-typeck-results.stderr

@@ -23,6 +23,7 @@ LL | |     });
    |
    = note: `fn(&'0 ()) -> std::future::Ready<&'0 ()> {std::future::ready::<&'0 ()>}` must implement `FnOnce<(&'1 (),)>`, for any two lifetimes `'0` and `'1`...
    = note: ...but it actually implements `FnOnce<(&(),)>`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 2 previous errors
 

tests/ui/async-await/return-type-notation/issue-110963-early.stderr

@@ -44,6 +44,7 @@ note: the lifetime requirement is introduced here
    |
 LL |     F: Future + Send + 'static,
    |                 ^^^^
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 2 previous errors; 1 warning emitted
 

tests/ui/borrowck/regions-bound-missing-bound-in-impl.stderr

@@ -53,6 +53,7 @@ note: ...does not necessarily outlive the lifetime `'c` as defined here
    |
 LL |     fn wrong_bound1<'b,'c,'d:'a+'c>(self, b: Inv<'b>, c: Inv<'c>, d: Inv<'d>) {
    |                        ^^
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0195]: lifetime parameters or bounds on method `wrong_bound2` do not match the trait declaration
   --> $DIR/regions-bound-missing-bound-in-impl.rs:42:20

tests/ui/cfg/future-compat-crate-attributes-using-cfg_attr.stderr

@@ -25,6 +25,7 @@ LL | #![cfg_attr(foo, crate_type="bin")]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #91632 <https://github.com/rust-lang/rust/issues/91632>
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `crate_name` within an `#![cfg_attr] attribute is deprecated`
   --> $DIR/future-compat-crate-attributes-using-cfg_attr.rs:9:18
@@ -34,6 +35,7 @@ LL | #![cfg_attr(foo, crate_name="bar")]
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #91632 <https://github.com/rust-lang/rust/issues/91632>
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 4 previous errors
 

tests/ui/conditional-compilation/cfg-attr-syntax-validation.stderr

@@ -74,6 +74,7 @@ LL |         #[cfg(feature = $expr)]
 LL | generate_s10!(concat!("nonexistent"));
    | ------------------------------------- in this macro invocation
    |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the macro `generate_s10` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 11 previous errors

tests/ui/const-generics/assoc_const_eq_diagnostic.stderr

@@ -39,6 +39,7 @@ note: associated constant defined here
    |
 LL |     const MODE: Mode;
    |     ^^^^^^^^^^^^^^^^
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 4 previous errors
 

tests/ui/const-generics/issues/issue-74950.min.stderr

@@ -15,6 +15,7 @@ LL | struct Outer<const I: Inner>;
    |
    = note: the only supported types are integers, `bool` and `char`
    = help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `Inner` is forbidden as the type of a const generic parameter
   --> $DIR/issue-74950.rs:20:23
@@ -24,6 +25,7 @@ LL | struct Outer<const I: Inner>;
    |
    = note: the only supported types are integers, `bool` and `char`
    = help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `Inner` is forbidden as the type of a const generic parameter
   --> $DIR/issue-74950.rs:20:23
@@ -33,6 +35,7 @@ LL | struct Outer<const I: Inner>;
    |
    = note: the only supported types are integers, `bool` and `char`
    = help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: `Inner` is forbidden as the type of a const generic parameter
   --> $DIR/issue-74950.rs:20:23
@@ -42,6 +45,7 @@ LL | struct Outer<const I: Inner>;
    |
    = note: the only supported types are integers, `bool` and `char`
    = help: add `#![feature(adt_const_params)]` to the crate attributes to enable more complex and user defined types
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 5 previous errors
 

tests/ui/consts/const-err-late.stderr

@@ -27,6 +27,8 @@ note: erroneous constant encountered
    |
 LL |     black_box((S::<i32>::FOO, S::<u32>::FOO));
    |                ^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to 2 previous errors
 

tests/ui/consts/const-eval/issue-44578.stderr

@@ -24,6 +24,7 @@ note: erroneous constant encountered
 LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT);
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this note originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error

tests/ui/consts/const-eval/panic-assoc-never-type.stderr

@@ -17,6 +17,8 @@ note: erroneous constant encountered
    |
 LL |     let _ = PrintName::VOID;
    |             ^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: aborting due to previous error
 

tests/ui/consts/const-eval/stable-metric/ctfe-simple-loop.warn.stderr

@@ -40,6 +40,7 @@ help: the constant being evaluated
    |
 LL | const Y: u32 = simple_loop(35);
    | ^^^^^^^^^^^^
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 warning: constant evaluation is taking a long time
   --> $DIR/ctfe-simple-loop.rs:9:5

tests/ui/consts/const_in_pattern/reject_non_structural.rs

@@ -1,3 +1,5 @@
+// compile-flags: -Zdeduplicate-diagnostics=yes
+
 // This test of structural match checking enumerates the different kinds of
 // const definitions, collecting cases where the const pattern is rejected.
 //
@@ -78,9 +80,6 @@ fn main() {
     //~^ ERROR must be annotated with `#[derive(PartialEq, Eq)]`
     //~| NOTE the traits must be derived
     //~| NOTE StructuralEq.html for details
-    //~| ERROR must be annotated with `#[derive(PartialEq, Eq)]`
-    //~| NOTE the traits must be derived
-    //~| NOTE StructuralEq.html for details
 
     trait Trait: Sized { const ASSOC: Option<Self>; }
     impl Trait for NoDerive { const ASSOC: Option<NoDerive> = Some(NoDerive); }

tests/ui/consts/const_in_pattern/reject_non_structural.stderr

@@ -1,5 +1,5 @@
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:40:36
+  --> $DIR/reject_non_structural.rs:42:36
    |
 LL |     match Derive::Some(NoDerive) { ENUM => dbg!(ENUM), _ => panic!("whoops"), };
    |                                    ^^^^
@@ -8,7 +8,7 @@ LL |     match Derive::Some(NoDerive) { ENUM => dbg!(ENUM), _ => panic!("whoops"
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:46:28
+  --> $DIR/reject_non_structural.rs:48:28
    |
 LL |     match Some(NoDerive) { FIELD => dbg!(FIELD), _ => panic!("whoops"), };
    |                            ^^^^^
@@ -17,7 +17,7 @@ LL |     match Some(NoDerive) { FIELD => dbg!(FIELD), _ => panic!("whoops"), };
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:53:27
+  --> $DIR/reject_non_structural.rs:55:27
    |
 LL |     match Some(NoDerive) {INDIRECT => dbg!(INDIRECT), _ => panic!("whoops"), };
    |                           ^^^^^^^^
@@ -26,7 +26,7 @@ LL |     match Some(NoDerive) {INDIRECT => dbg!(INDIRECT), _ => panic!("whoops")
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:59:36
+  --> $DIR/reject_non_structural.rs:61:36
    |
 LL |     match (None, Some(NoDerive)) { TUPLE => dbg!(TUPLE), _ => panic!("whoops"), };
    |                                    ^^^^^
@@ -35,7 +35,7 @@ LL |     match (None, Some(NoDerive)) { TUPLE => dbg!(TUPLE), _ => panic!("whoop
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:65:28
+  --> $DIR/reject_non_structural.rs:67:28
    |
 LL |     match Some(NoDerive) { TYPE_ASCRIPTION => dbg!(TYPE_ASCRIPTION), _ => panic!("whoops"), };
    |                            ^^^^^^^^^^^^^^^
@@ -44,7 +44,7 @@ LL |     match Some(NoDerive) { TYPE_ASCRIPTION => dbg!(TYPE_ASCRIPTION), _ => p
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:71:36
+  --> $DIR/reject_non_structural.rs:73:36
    |
 LL |     match [None, Some(NoDerive)] { ARRAY => dbg!(ARRAY), _ => panic!("whoops"), };
    |                                    ^^^^^
@@ -53,7 +53,7 @@ LL |     match [None, Some(NoDerive)] { ARRAY => dbg!(ARRAY), _ => panic!("whoop
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:77:33
+  --> $DIR/reject_non_structural.rs:79:33
    |
 LL |     match [Some(NoDerive); 2] { REPEAT => dbg!(REPEAT), _ => panic!("whoops"), };
    |                                 ^^^^^^
@@ -62,16 +62,7 @@ LL |     match [Some(NoDerive); 2] { REPEAT => dbg!(REPEAT), _ => panic!("whoops
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:77:33
-   |
-LL |     match [Some(NoDerive); 2] { REPEAT => dbg!(REPEAT), _ => panic!("whoops"), };
-   |                                 ^^^^^^
-   |
-   = note: the traits must be derived, manual `impl`s are not sufficient
-   = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
-
-error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:87:28
+  --> $DIR/reject_non_structural.rs:86:28
    |
 LL |     match Some(NoDerive) { NoDerive::ASSOC => dbg!(NoDerive::ASSOC), _ => panic!("whoops"), };
    |                            ^^^^^^^^^^^^^^^
@@ -80,7 +71,7 @@ LL |     match Some(NoDerive) { NoDerive::ASSOC => dbg!(NoDerive::ASSOC), _ => p
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 error: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:93:28
+  --> $DIR/reject_non_structural.rs:92:28
    |
 LL |     match Some(NoDerive) { BLOCK => dbg!(BLOCK), _ => panic!("whoops"), };
    |                            ^^^^^
@@ -89,7 +80,7 @@ LL |     match Some(NoDerive) { BLOCK => dbg!(BLOCK), _ => panic!("whoops"), };
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 
 warning: to use a constant of type `NoDerive` in a pattern, `NoDerive` must be annotated with `#[derive(PartialEq, Eq)]`
-  --> $DIR/reject_non_structural.rs:99:29
+  --> $DIR/reject_non_structural.rs:98:29
    |
 LL |     match &Some(NoDerive) { ADDR_OF => dbg!(ADDR_OF), _ => panic!("whoops"), };
    |                             ^^^^^^^
@@ -99,10 +90,10 @@ LL |     match &Some(NoDerive) { ADDR_OF => dbg!(ADDR_OF), _ => panic!("whoops")
    = note: the traits must be derived, manual `impl`s are not sufficient
    = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details
 note: the lint level is defined here
-  --> $DIR/reject_non_structural.rs:12:9
+  --> $DIR/reject_non_structural.rs:14:9
    |
 LL | #![warn(indirect_structural_match)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 10 previous errors; 1 warning emitted
+error: aborting due to 9 previous errors; 1 warning emitted
 

tests/ui/consts/enum-discr-type-err.stderr

@@ -24,6 +24,7 @@ LL | |     B = T,
 LL | | }
    | |_- in this macro invocation
    |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
    = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors