Don't hash lints differently to non-lints.

compiler/rustc_errors/src/diagnostic.rs

@@ -109,8 +109,6 @@ pub struct Diagnostic {
  /// `span` if there is one. Otherwise, it is `DUMMY_SP`.
  pub sort_span: Span,
 
- /// If diagnostic is from Lint, custom hash function ignores children.
- /// Otherwise hash is based on the all the fields.
  pub is_lint: Option<IsLint>,
 
  /// With `-Ztrack_diagnostics` enabled,
@@ -980,22 +978,24 @@ impl Diagnostic {
  ) -> (
  &Level,
  &[(DiagnosticMessage, Style)],
- Vec<(&Cow<'static, str>, &DiagnosticArgValue)>,
  &Option<ErrCode>,
- &Option<IsLint>,
  &MultiSpan,
+ &[SubDiagnostic],
  &Result<Vec<CodeSuggestion>, SuggestionsDisabled>,
- Option<&[SubDiagnostic]>,
+ Vec<(&DiagnosticArgName, &DiagnosticArgValue)>,
+ &Option<IsLint>,
  ) {
  (
  &self.level,
  &self.messages,
- self.args().collect(),
  &self.code,
- &self.is_lint,
  &self.span,
+ &self.children,
  &self.suggestions,
- (if self.is_lint.is_some() { None } else { Some(&self.children) }),
+ self.args().collect(),
+ // omit self.sort_span
+ &self.is_lint,
+ // omit self.emitted_at
  )
  }
 }

src/tools/clippy/tests/ui/same_name_method.rs

@@ -74,6 +74,7 @@ mod should_lint {
  impl S {
  fn foo() {}
  //~^ ERROR: method's name is the same as an existing method in a trait
+ //~| ERROR: method's name is the same as an existing method in a trait
  }
 
  impl T1 for S {}

src/tools/clippy/tests/ui/same_name_method.stderr

@@ -56,10 +56,22 @@ LL | fn foo() {}
  | ^^^^^^^^^^^
  |
 note: existing `foo` defined here
- --> $DIR/same_name_method.rs:79:9
+ --> $DIR/same_name_method.rs:80:9
  |
 LL | impl T1 for S {}
  | ^^^^^^^^^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: method's name is the same as an existing method in a trait
+ --> $DIR/same_name_method.rs:75:13
+ |
+LL | fn foo() {}
+ | ^^^^^^^^^^^
+ |
+note: existing `foo` defined here
+ --> $DIR/same_name_method.rs:82:9
+ |
+LL | impl T2 for S {}
+ | ^^^^^^^^^^^^^^^^
+
+error: aborting due to 6 previous errors
 

tests/rustdoc-ui/unescaped_backticks.stderr

@@ -302,7 +302,6 @@ LL | | /// level changes.
  = help: if you meant to use a literal backtick, escape it
  change: or `None` if it isn't.
  to this: or `None\` if it isn't.
- = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: unescaped backtick
  --> $DIR/unescaped_backticks.rs:323:5
@@ -322,7 +321,6 @@ LL | | /// level changes.
  = help: if you meant to use a literal backtick, escape it
  change: `on_event` should be called.
  to this: `on_event\` should be called.
- = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: unescaped backtick
  --> $DIR/unescaped_backticks.rs:323:5
@@ -342,7 +340,6 @@ LL | | /// level changes.
  = help: if you meant to use a literal backtick, escape it
  change: [`rebuild_interest_cache`][rebuild] is called after the value of the max
  to this: [`rebuild_interest_cache\`][rebuild] is called after the value of the max
- = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error: unescaped backtick
  --> $DIR/unescaped_backticks.rs:349:56

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

@@ -40,7 +40,6 @@ 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/imports/ambiguous-9.stderr

@@ -60,7 +60,6 @@ note: `date_range` could also refer to the function imported here
 LL | use prelude::*;
  | ^^^^^^^^^^
  = help: consider adding an explicit import of `date_range` to disambiguate
- = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 warning: 4 warnings emitted