Auto merge of #45519 - michaelwoerister:dedup-errors, r=arielb1

Don't emit the same compiler diagnostic twice.

This PR makes the compiler filter out diagnostic messages that have already been emitted during the same compilation session.

src/Cargo.lock

@@ -1681,6 +1681,7 @@ dependencies = [
 name = "rustc_errors"
 version = "0.0.0"
 dependencies = [
+ "rustc_data_structures 0.0.0",
  "serialize 0.0.0",
  "syntax_pos 0.0.0",
 ]

src/etc/generate-deriving-span-tests.py

@@ -74,7 +74,7 @@ struct Struct(
 
 ENUM_TUPLE, ENUM_STRUCT, STRUCT_FIELDS, STRUCT_TUPLE = range(4)
 
-def create_test_case(type, trait, super_traits, number_of_errors):
+def create_test_case(type, trait, super_traits, error_count):
     string = [ENUM_STRING, ENUM_STRUCT_VARIANT_STRING, STRUCT_STRING, STRUCT_TUPLE_STRING][type]
     all_traits = ','.join([trait] + super_traits)
     super_traits = ','.join(super_traits)
@@ -113,7 +113,7 @@ traits = {
 
 for (trait, supers, errs) in [('Clone', [], 1),
                               ('PartialEq', [], 2),
-                              ('PartialOrd', ['PartialEq'], 9),
+                              ('PartialOrd', ['PartialEq'], 3),
                               ('Eq', ['PartialEq'], 1),
                               ('Ord', ['Eq', 'PartialOrd', 'PartialEq'], 1),
                               ('Debug', [], 1),

src/librustc_errors/Cargo.toml

@@ -11,3 +11,4 @@ crate-type = ["dylib"]
 [dependencies]
 serialize = { path = "../libserialize" }
 syntax_pos = { path = "../libsyntax_pos" }
+rustc_data_structures = { path = "../librustc_data_structures" }

src/librustc_errors/diagnostic.rs

@@ -17,7 +17,7 @@ use syntax_pos::{MultiSpan, Span};
 use snippet::Style;
 
 #[must_use]
-#[derive(Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 pub struct Diagnostic {
     pub level: Level,
     pub message: Vec<(String, Style)>,
@@ -28,7 +28,7 @@ pub struct Diagnostic {
 }
 
 /// For example a note attached to an error.
-#[derive(Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 pub struct SubDiagnostic {
     pub level: Level,
     pub message: Vec<(String, Style)>,

src/librustc_errors/lib.rs

@@ -18,10 +18,12 @@
 #![feature(range_contains)]
 #![cfg_attr(unix, feature(libc))]
 #![feature(conservative_impl_trait)]
+#![feature(i128_type)]
 
 extern crate term;
 #[cfg(unix)]
 extern crate libc;
+extern crate rustc_data_structures;
 extern crate serialize as rustc_serialize;
 extern crate syntax_pos;
 
@@ -31,6 +33,9 @@ use self::Level::*;
 
 use emitter::{Emitter, EmitterWriter};
 
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::stable_hasher::StableHasher;
+
 use std::borrow::Cow;
 use std::cell::{RefCell, Cell};
 use std::mem;
@@ -47,7 +52,7 @@ mod lock;
 
 use syntax_pos::{BytePos, Loc, FileLinesResult, FileMap, FileName, MultiSpan, Span, NO_EXPANSION};
 
-#[derive(Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 pub enum RenderSpan {
     /// A FullSpan renders with both with an initial line for the
     /// message, prefixed by file:linenum, followed by a summary of
@@ -61,7 +66,7 @@ pub enum RenderSpan {
     Suggestion(CodeSuggestion),
 }
 
-#[derive(Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 pub struct CodeSuggestion {
     /// Each substitute can have multiple variants due to multiple
     /// applicable suggestions
@@ -86,7 +91,7 @@ pub struct CodeSuggestion {
     pub show_code_when_inline: bool,
 }
 
-#[derive(Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 /// See the docs on `CodeSuggestion::substitutions`
 pub struct Substitution {
     pub span: Span,
@@ -271,6 +276,11 @@ pub struct Handler {
     continue_after_error: Cell<bool>,
     delayed_span_bug: RefCell<Option<Diagnostic>>,
     tracked_diagnostics: RefCell<Option<Vec<Diagnostic>>>,
+
+    // This set contains a hash of every diagnostic that has been emitted by
+    // this handler. These hashes is used to avoid emitting the same error
+    // twice.
+    emitted_diagnostics: RefCell<FxHashSet<u128>>,
 }
 
 impl Handler {
@@ -295,6 +305,7 @@ impl Handler {
             continue_after_error: Cell::new(true),
             delayed_span_bug: RefCell::new(None),
             tracked_diagnostics: RefCell::new(None),
+            emitted_diagnostics: RefCell::new(FxHashSet()),
         }
     }
 
@@ -559,15 +570,29 @@ impl Handler {
     }
 
     fn emit_db(&self, db: &DiagnosticBuilder) {
+        let diagnostic = &**db;
+
         if let Some(ref mut list) = *self.tracked_diagnostics.borrow_mut() {
-            list.push((**db).clone());
+            list.push(diagnostic.clone());
+        }
+
+        let diagnostic_hash = {
+            use std::hash::Hash;
+            let mut hasher = StableHasher::new();
+            diagnostic.hash(&mut hasher);
+            hasher.finish()
+        };
+
+        // Only emit the diagnostic if we haven't already emitted an equivalent
+        // one:
+        if self.emitted_diagnostics.borrow_mut().insert(diagnostic_hash) {
+            self.emitter.borrow_mut().emit(db);
         }
-        self.emitter.borrow_mut().emit(db);
     }
 }
 
 
-#[derive(Copy, PartialEq, Clone, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, PartialEq, Clone, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub enum Level {
     Bug,
     Fatal,

src/librustc_errors/snippet.rs

@@ -203,7 +203,7 @@ pub struct StyledString {
     pub style: Style,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, Debug, PartialEq, Hash, RustcEncodable, RustcDecodable)]
 pub enum Style {
     HeaderMsg,
     LineAndColumn,

src/test/compile-fail/E0017.rs

@@ -13,15 +13,9 @@ const C: i32 = 2;
 
 const CR: &'static mut i32 = &mut C; //~ ERROR E0017
                                      //~| NOTE constants require immutable values
-                                     //~| ERROR E0017
-                                     //~| NOTE constants require immutable values
 static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
-                                              //~| NOTE statics require immutable values
-                                              //~| ERROR E0017
                                               //~| NOTE statics require immutable values
                                               //~| ERROR cannot borrow
 static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0017
                                              //~| NOTE statics require immutable values
-                                             //~| ERROR E0017
-                                             //~| NOTE statics require immutable values
 fn main() {}

src/test/compile-fail/E0388.rs

@@ -12,11 +12,8 @@ static X: i32 = 1;
 const C: i32 = 2;
 
 const CR: &'static mut i32 = &mut C; //~ ERROR E0017
-                                     //~| ERROR E0017
 static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
-                                              //~| ERROR E0017
                                               //~| ERROR cannot borrow
 static CONST_REF: &'static mut i32 = &mut C; //~ ERROR E0017
-                                             //~| ERROR E0017
 
 fn main() {}

src/test/compile-fail/borrowck/borrowck-overloaded-call.rs

@@ -67,7 +67,6 @@ fn f() {
     };
     let sp = &mut s;
     s(3);   //~ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable
-    //~^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable
 }
 
 fn g() {

src/test/compile-fail/borrowck/borrowck-unboxed-closures.rs

@@ -11,7 +11,6 @@
 fn a<F:Fn(isize, isize) -> isize>(mut f: F) {
     let g = &mut f;
     f(1, 2);    //~ ERROR cannot borrow `f` as immutable
-    //~^ ERROR cannot borrow `f` as immutable
 }
 
 fn b<F:FnMut(isize, isize) -> isize>(f: F) {

src/test/compile-fail/check-static-immutable-mut-slices.rs

@@ -12,6 +12,5 @@
 
 static TEST: &'static mut [isize] = &mut [];
 //~^ ERROR references in statics may only refer to immutable values
-//~^^ ERROR references in statics may only refer to immutable values
 
 pub fn main() { }

src/test/compile-fail/const-err.rs

@@ -24,8 +24,6 @@ fn black_box<T>(_: T) {
 const FOO: u8 = [5u8][1];
 //~^ ERROR constant evaluation error
 //~| index out of bounds: the len is 1 but the index is 1
-//~^^^ ERROR constant evaluation error
-//~| index out of bounds: the len is 1 but the index is 1
 
 fn main() {
     let a = -std::i8::MIN;
@@ -33,8 +31,7 @@ fn main() {
     //~| attempt to negate with overflow
     let b = 200u8 + 200u8 + 200u8;
     //~^ WARN this expression will panic at run-time
-    //~| attempt to add with overflow
+    //~^^ WARN this expression will panic at run-time
-    //~^^^ WARN this expression will panic at run-time
     //~| attempt to add with overflow
     let c = 200u8 * 4;
     //~^ WARN this expression will panic at run-time

src/test/compile-fail/const-err2.rs

@@ -21,7 +21,6 @@ fn main() {
     //~^ ERROR attempt to negate with overflow
     let b = 200u8 + 200u8 + 200u8;
     //~^ ERROR attempt to add with overflow
-    //~| ERROR attempt to add with overflow
     let c = 200u8 * 4;
     //~^ ERROR attempt to multiply with overflow
     let d = 42u8 - (42u8 + 1);

src/test/compile-fail/cycle-trait-default-type-trait.rs

@@ -13,7 +13,6 @@
 
 trait Foo<X = Box<Foo>> {
     //~^ ERROR unsupported cyclic reference
-    //~| ERROR unsupported cyclic reference
 }
 
 fn main() { }

src/test/compile-fail/derives-span-Clone-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Clone-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Clone-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Clone-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Debug-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Debug-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Debug-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Debug-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Default-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -15,7 +15,7 @@ struct Error;
 
 #[derive(Default)]
 struct Struct {
-    x: Error //~ ERROR `Error: std::default::Default` is not satisfied
+    x: Error //~ ERROR
 }
 
 fn main() {}

src/test/compile-fail/derives-span-Default-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Eq-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Eq-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Eq-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Eq-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Hash-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Hash-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Hash-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Hash-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Ord-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Ord-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Ord-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-Ord-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-PartialEq-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-PartialEq-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-PartialEq-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-PartialEq-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //

src/test/compile-fail/derives-span-PartialOrd-enum-struct-variant.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -19,12 +19,6 @@ enum Enum {
      x: Error //~ ERROR
 //~^ ERROR
 //~^^ ERROR
-//~^^^ ERROR
-//~^^^^ ERROR
-//~^^^^^ ERROR
-//~^^^^^^ ERROR
-//~^^^^^^^ ERROR
-//~^^^^^^^^ ERROR
    }
 }
 

src/test/compile-fail/derives-span-PartialOrd-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -19,12 +19,6 @@ enum Enum {
      Error //~ ERROR
 //~^ ERROR
 //~^^ ERROR
-//~^^^ ERROR
-//~^^^^ ERROR
-//~^^^^^ ERROR
-//~^^^^^^ ERROR
-//~^^^^^^^ ERROR
-//~^^^^^^^^ ERROR
      )
 }
 

src/test/compile-fail/derives-span-PartialOrd-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -18,12 +18,6 @@ struct Struct {
     x: Error //~ ERROR
 //~^ ERROR
 //~^^ ERROR
-//~^^^ ERROR
-//~^^^^ ERROR
-//~^^^^^ ERROR
-//~^^^^^^ ERROR
-//~^^^^^^^ ERROR
-//~^^^^^^^^ ERROR
 }
 
 fn main() {}

src/test/compile-fail/derives-span-PartialOrd-tuple-struct.rs

@@ -1,4 +1,4 @@
-// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -18,12 +18,6 @@ struct Struct(
     Error //~ ERROR
 //~^ ERROR
 //~^^ ERROR
-//~^^^ ERROR
-//~^^^^ ERROR
-//~^^^^^ ERROR
-//~^^^^^^ ERROR
-//~^^^^^^^ ERROR
-//~^^^^^^^^ ERROR
 );
 
 fn main() {}

src/test/compile-fail/feature-gate/issue-43106-gating-of-rustc_deprecated.rs

@@ -28,7 +28,6 @@ mod rustc_deprecated {
 
     #[rustc_deprecated = "1500"] struct S;
     //~^ ERROR stability attributes may not be used outside of the standard library
-    //~| ERROR stability attributes may not be used outside of the standard library
 
     #[rustc_deprecated = "1500"] type T = S;
     //~^ ERROR stability attributes may not be used outside of the standard library

src/test/compile-fail/feature-gate/issue-43106-gating-of-stable.rs

@@ -28,7 +28,6 @@ mod stable {
 
     #[stable = "1300"] struct S;
     //~^ ERROR stability attributes may not be used outside of the standard library
-    //~| ERROR stability attributes may not be used outside of the standard library
 
     #[stable = "1300"] type T = S;
     //~^ ERROR stability attributes may not be used outside of the standard library

src/test/compile-fail/feature-gate/issue-43106-gating-of-unstable.rs

@@ -28,7 +28,6 @@ mod unstable {
 
     #[unstable = "1200"] struct S;
     //~^ ERROR stability attributes may not be used outside of the standard library
-    //~| ERROR stability attributes may not be used outside of the standard library
 
     #[unstable = "1200"] type T = S;
     //~^ ERROR stability attributes may not be used outside of the standard library

src/test/compile-fail/issue-17718-const-bad-values.rs

@@ -10,13 +10,11 @@
 
 const C1: &'static mut [usize] = &mut [];
 //~^ ERROR: references in constants may only refer to immutable values
-//~| ERROR: references in constants may only refer to immutable values
 
 static mut S: usize = 3;
 const C2: &'static mut usize = unsafe { &mut S };
 //~^ ERROR: constants cannot refer to statics
 //~| ERROR: references in constants may only refer to immutable values
 //~| ERROR: references in constants may only refer to immutable values
-//~| ERROR: references in constants may only refer to immutable values
 
 fn main() {}

src/test/compile-fail/issue-20831-debruijn.rs

@@ -38,7 +38,6 @@ impl<'a> Publisher<'a> for MyStruct<'a> {
     fn subscribe(&mut self, t : Box<Subscriber<Input=<Self as Publisher>::Output> + 'a>) {
         // Not obvious, but there is an implicit lifetime here -------^
         //~^^ ERROR cannot infer
-        //~|  ERROR cannot infer
         //
         // The fact that `Publisher` is using an implicit lifetime is
         // what was causing the debruijn accounting to be off, so

src/test/compile-fail/issue-41255.rs

@@ -39,8 +39,6 @@ fn main() {
     match (x, 5) {
         (3.14, 1) => {}, //~ ERROR floating-point literals cannot be used
                          //~| WARNING hard error
-                         //~| ERROR floating-point literals cannot be used
-                         //~| WARNING hard error
         _ => {},
     }
     // Or structs
@@ -48,8 +46,6 @@ fn main() {
     match (Foo { x }) {
         Foo { x: 2.0 } => {}, //~ ERROR floating-point literals cannot be used
                               //~| WARNING hard error
-                              //~| ERROR floating-point literals cannot be used
-                              //~| WARNING hard error
         _ => {},
     }
 }

src/test/compile-fail/lint-stability-deprecated.rs

@@ -107,7 +107,6 @@ mod cross_crate {
         struct S1<T: TraitWithAssociatedTypes>(T::TypeUnstable);
         struct S2<T: TraitWithAssociatedTypes>(T::TypeDeprecated);
         //~^ WARN use of deprecated item
-        //~| WARN use of deprecated item
 
         let _ = DeprecatedStruct { //~ WARN use of deprecated item
             i: 0 //~ WARN use of deprecated item

src/test/compile-fail/patkind-litrange-no-expr.rs

@@ -28,8 +28,7 @@ enum_number!(Change {
     Pos = 1,
     Neg = -1,
     Arith = 1 + 1, //~ ERROR arbitrary expressions aren't allowed in patterns
-                   //~^ ERROR arbitrary expressions aren't allowed in patterns
+                   //~^ ERROR only char and numeric types are allowed in range patterns
-                   //~^^ ERROR only char and numeric types are allowed in range patterns
 });
 
 fn main() {}

src/test/compile-fail/range_traits-1.rs

@@ -12,75 +12,38 @@
 
 use std::ops::*;
 
-// FIXME #34229 duplicated errors
 #[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 struct AllTheRanges {
     a: Range<usize>,
     //~^ ERROR PartialOrd
     //~^^ ERROR Ord
-    //~^^^ ERROR binary operation
+    //~^^^ ERROR binary operation `<` cannot be applied to type
-    //~^^^^ ERROR binary operation
+    //~^^^^ ERROR binary operation `>` cannot be applied to type
-    //~^^^^^ ERROR binary operation
-    //~^^^^^^ ERROR binary operation
-    //~^^^^^^^ ERROR binary operation
-    //~^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^^ ERROR binary operation
     b: RangeTo<usize>,
     //~^ ERROR PartialOrd
     //~^^ ERROR Ord
-    //~^^^ ERROR binary operation
+    //~^^^ ERROR binary operation `<` cannot be applied to type
-    //~^^^^ ERROR binary operation
+    //~^^^^ ERROR binary operation `>` cannot be applied to type
-    //~^^^^^ ERROR binary operation
-    //~^^^^^^ ERROR binary operation
-    //~^^^^^^^ ERROR binary operation
-    //~^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^^ ERROR binary operation
     c: RangeFrom<usize>,
     //~^ ERROR PartialOrd
     //~^^ ERROR Ord
-    //~^^^ ERROR binary operation
+    //~^^^ ERROR binary operation `<` cannot be applied to type
-    //~^^^^ ERROR binary operation
+    //~^^^^ ERROR binary operation `>` cannot be applied to type
-    //~^^^^^ ERROR binary operation
-    //~^^^^^^ ERROR binary operation
-    //~^^^^^^^ ERROR binary operation
-    //~^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^^ ERROR binary operation
     d: RangeFull,
     //~^ ERROR PartialOrd
     //~^^ ERROR Ord
-    //~^^^ ERROR binary operation
+    //~^^^ ERROR binary operation `<` cannot be applied to type
-    //~^^^^ ERROR binary operation
+    //~^^^^ ERROR binary operation `>` cannot be applied to type
-    //~^^^^^ ERROR binary operation
-    //~^^^^^^ ERROR binary operation
-    //~^^^^^^^ ERROR binary operation
-    //~^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^^ ERROR binary operation
     e: RangeInclusive<usize>,
     //~^ ERROR PartialOrd
     //~^^ ERROR Ord
-    //~^^^ ERROR binary operation
+    //~^^^ ERROR binary operation `<` cannot be applied to type
-    //~^^^^ ERROR binary operation
+    //~^^^^ ERROR binary operation `>` cannot be applied to type
-    //~^^^^^ ERROR binary operation
-    //~^^^^^^ ERROR binary operation
-    //~^^^^^^^ ERROR binary operation
-    //~^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^^ ERROR binary operation
     f: RangeToInclusive<usize>,
     //~^ ERROR PartialOrd
     //~^^ ERROR Ord
-    //~^^^ ERROR binary operation
+    //~^^^ ERROR binary operation `<` cannot be applied to type
-    //~^^^^ ERROR binary operation
+    //~^^^^ ERROR binary operation `>` cannot be applied to type
-    //~^^^^^ ERROR binary operation
-    //~^^^^^^ ERROR binary operation
-    //~^^^^^^^ ERROR binary operation
-    //~^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^ ERROR binary operation
-    //~^^^^^^^^^^ ERROR binary operation
 }
 
 fn main() {}

src/test/compile-fail/regions-bound-missing-bound-in-impl.rs

@@ -35,7 +35,6 @@ impl<'a, 't> Foo<'a, 't> for &'a isize {
 
     fn wrong_bound1<'b,'c,'d:'a+'c>(self, b: Inv<'b>, c: Inv<'c>, d: Inv<'d>) {
         //~^ ERROR method not compatible with trait
-        //~^^ ERROR method not compatible with trait
         //
         // Note: This is a terrible error message. It is caused
         // because, in the trait, 'b is early bound, and in the impl,

src/test/compile-fail/regions-close-object-into-object-5.rs

@@ -31,7 +31,6 @@ fn f<'a, T, U>(v: Box<A<T>+'static>) -> Box<X+'static> {
         //~| ERROR the parameter type `T` may not live long enough
         //~| ERROR the parameter type `T` may not live long enough
         //~| ERROR the parameter type `T` may not live long enough
-        //~| ERROR the parameter type `T` may not live long enough
 }
 
 fn main() {}

src/test/ui/span/macro-ty-params.stderr

@@ -4,12 +4,6 @@ error: unexpected generic arguments in path
 20 |     m!(MyTrait<>);
    |        ^^^^^^^^^
 
-error: unexpected generic arguments in path
-  --> $DIR/macro-ty-params.rs:20:8
-   |
-20 |     m!(MyTrait<>);
-   |        ^^^^^^^^^
-
 error: generic arguments in macro path
   --> $DIR/macro-ty-params.rs:18:8
    |