Add a note to duplicate diagnostics

Author: Alexendoo

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 +1401,11 @@ 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