Auto merge of #50724 - zackmdavis:applicability_rush, r=Manishearth

add suggestion applicabilities to librustc and libsyntax

A down payment on #50723. Interested in feedback on whether my `MaybeIncorrect` vs. `MachineApplicable` judgement calls are well-calibrated (and that we have a consensus on what this means).

r? @Manishearth
cc @killercup @estebank

25 files changed, 218 insertions, 28 deletions

diff --git a/src/test/ui/extern-const.fixed b/src/test/ui/extern-const.fixed
new file mode 100644
index 00000000000..6e131ca41aa
--- /dev/null
+++ b/src/test/ui/extern-const.fixed
@@ -0,0 +1,25 @@
+// 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.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+// compile-flags: -Z continue-parse-after-error
+
+extern "C" {
+    static C: u8; //~ ERROR extern items cannot be `const`
+}
+
+fn main() {
+    // We suggest turning the (illegal) extern `const` into an extern `static`,
+    // but this also requires `unsafe` (a deny-by-default lint at comment time,
+    // future error; Issue #36247)
+    unsafe {
+        let _x = C;
+    }
+}
diff --git a/src/test/ui/extern-const.rs b/src/test/ui/extern-const.rs
index a77d7b11895..4a766b9724d 100644
--- a/src/test/ui/extern-const.rs
+++ b/src/test/ui/extern-const.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// run-rustfix
 // compile-flags: -Z continue-parse-after-error
 
 extern "C" {
@@ -15,5 +16,10 @@ extern "C" {
 }
 
 fn main() {
-    let x = C;
+    // We suggest turning the (illegal) extern `const` into an extern `static`,
+    // but this also requires `unsafe` (a deny-by-default lint at comment time,
+    // future error; Issue #36247)
+    unsafe {
+        let _x = C;
+    }
 }
diff --git a/src/test/ui/extern-const.stderr b/src/test/ui/extern-const.stderr
index f416f596b25..cbed5e56c76 100644
--- a/src/test/ui/extern-const.stderr
+++ b/src/test/ui/extern-const.stderr
@@ -1,8 +1,8 @@
 error: extern items cannot be `const`
-  --> $DIR/extern-const.rs:14:5
+  --> $DIR/extern-const.rs:15:5
    |
 LL |     const C: u8; //~ ERROR extern items cannot be `const`
-   |     ^^^^^ help: instead try using: `static`
+   |     ^^^^^ help: try using a static value: `static`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/issue-42954.fixed b/src/test/ui/issue-42954.fixed
new file mode 100644
index 00000000000..d05996fb8b9
--- /dev/null
+++ b/src/test/ui/issue-42954.fixed
@@ -0,0 +1,24 @@
+// 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.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+#![allow(unused_must_use, unused_comparisons)]
+
+macro_rules! is_plainly_printable {
+    ($i: ident) => {
+        ($i as u32) < 0 //~ `<` is interpreted as a start of generic arguments
+    };
+}
+
+fn main() {
+    let c = 'a';
+    is_plainly_printable!(c);
+}
diff --git a/src/test/ui/issue-42954.rs b/src/test/ui/issue-42954.rs
index 6fa2c69bf66..8226cedc0c4 100644
--- a/src/test/ui/issue-42954.rs
+++ b/src/test/ui/issue-42954.rs
@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// run-rustfix
+
+#![allow(unused_must_use, unused_comparisons)]
+
 macro_rules! is_plainly_printable {
     ($i: ident) => {
         $i as u32 < 0 //~ `<` is interpreted as a start of generic arguments
diff --git a/src/test/ui/issue-42954.stderr b/src/test/ui/issue-42954.stderr
index 9164434006f..aa332602f9e 100644
--- a/src/test/ui/issue-42954.stderr
+++ b/src/test/ui/issue-42954.stderr
@@ -1,5 +1,5 @@
 error: `<` is interpreted as a start of generic arguments for `u32`, not a comparison
-  --> $DIR/issue-42954.rs:13:19
+  --> $DIR/issue-42954.rs:17:19
    |
 LL |         $i as u32 < 0 //~ `<` is interpreted as a start of generic arguments
    |         --------- ^ - interpreted as generic arguments
diff --git a/src/test/ui/issue-44406.stderr b/src/test/ui/issue-44406.stderr
index de7c11732e4..5cd9b3f065e 100644
--- a/src/test/ui/issue-44406.stderr
+++ b/src/test/ui/issue-44406.stderr
@@ -8,7 +8,7 @@ error: expected type, found keyword `true`
   --> $DIR/issue-44406.rs:18:10
    |
 LL |         bar(baz: $rest)
-   |                - help: did you mean to use `;` here?
+   |                - help: try using a semicolon: `;`
 ...
 LL |     foo!(true); //~ ERROR expected type, found keyword
    |          ^^^^ expecting a type here because of type ascription
diff --git a/src/test/ui/issue-48636.fixed b/src/test/ui/issue-48636.fixed
new file mode 100644
index 00000000000..0ff33c42b1c
--- /dev/null
+++ b/src/test/ui/issue-48636.fixed
@@ -0,0 +1,21 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+#![allow(dead_code)]
+
+struct S {
+    x: u8,
+    /// The id of the parent core
+    y: u8,
+}
+//~^^^ ERROR found a documentation comment that doesn't document anything
+fn main() {}
diff --git a/src/test/ui/issue-48636.rs b/src/test/ui/issue-48636.rs
index 03e45d88e6c..2ac41211347 100644
--- a/src/test/ui/issue-48636.rs
+++ b/src/test/ui/issue-48636.rs
@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// run-rustfix
+
+#![allow(dead_code)]
+
 struct S {
     x: u8
     /// The id of the parent core
diff --git a/src/test/ui/issue-48636.stderr b/src/test/ui/issue-48636.stderr
index 4e014a5bd1d..c4706f982ed 100644
--- a/src/test/ui/issue-48636.stderr
+++ b/src/test/ui/issue-48636.stderr
@@ -1,5 +1,5 @@
 error[E0585]: found a documentation comment that doesn't document anything
-  --> $DIR/issue-48636.rs:13:5
+  --> $DIR/issue-48636.rs:17:5
    |
 LL |     x: u8
    |          - help: missing comma here: `,`
diff --git a/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.fixed b/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.fixed
new file mode 100644
index 00000000000..1a7608fea6e
--- /dev/null
+++ b/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.fixed
@@ -0,0 +1,30 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Regression test for #47244: in this specific scenario, when the
+// expected type indicated 1 argument but the closure takes two, we
+// would (early on) create type variables for the type of `b`. If the
+// user then attempts to invoke a method on `b`, we would get an error
+// saying that the type of `b` must be known, which was not very
+// helpful.
+
+// run-rustfix
+
+use std::collections::HashMap;
+
+fn main() {
+    let mut m = HashMap::new();
+    m.insert("foo", "bar");
+
+    let _n = m.iter().map(|(_, b)| {
+        //~^ ERROR closure is expected to take a single 2-tuple
+        b.to_string()
+    });
+}
diff --git a/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.rs b/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.rs
index b6463ca067b..0ca0753490a 100644
--- a/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.rs
+++ b/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.rs
@@ -15,15 +15,16 @@
 // saying that the type of `b` must be known, which was not very
 // helpful.
 
+// run-rustfix
+
 use std::collections::HashMap;
-fn main() {
 
-    let m = HashMap::new();
-    m.insert( "foo", "bar" );
+fn main() {
+    let mut m = HashMap::new();
+    m.insert("foo", "bar");
 
-    m.iter().map( |_, b| {
+    let _n = m.iter().map(|_, b| {
         //~^ ERROR closure is expected to take a single 2-tuple
-
         b.to_string()
     });
 }
diff --git a/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.stderr b/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.stderr
index 262c4aa1a7c..c95d8157b0c 100644
--- a/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.stderr
+++ b/src/test/ui/mismatched_types/closure-arg-count-expected-type-issue-47244.stderr
@@ -1,14 +1,14 @@
 error[E0593]: closure is expected to take a single 2-tuple as argument, but it takes 2 distinct arguments
-  --> $DIR/closure-arg-count-expected-type-issue-47244.rs:24:14
+  --> $DIR/closure-arg-count-expected-type-issue-47244.rs:26:23
    |
-LL |     m.iter().map( |_, b| {
-   |              ^^^  ------ takes 2 distinct arguments
-   |              |
-   |              expected closure that takes a single 2-tuple as argument
+LL |     let _n = m.iter().map(|_, b| {
+   |                       ^^^ ------ takes 2 distinct arguments
+   |                       |
+   |                       expected closure that takes a single 2-tuple as argument
 help: change the closure to accept a tuple instead of individual arguments
    |
-LL |     m.iter().map( |(_, b)| {
-   |                   ^^^^^^^^
+LL |     let _n = m.iter().map(|(_, b)| {
+   |                           ^^^^^^^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/repr-align-assign.fixed b/src/test/ui/repr-align-assign.fixed
new file mode 100644
index 00000000000..62147e7625e
--- /dev/null
+++ b/src/test/ui/repr-align-assign.fixed
@@ -0,0 +1,21 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+#![allow(dead_code)]
+
+#[repr(align(8))] //~ ERROR incorrect `repr(align)` attribute format
+struct A(u64);
+
+#[repr(align(8))] //~ ERROR incorrect `repr(align)` attribute format
+struct B(u64);
+
+fn main() {}
diff --git a/src/test/ui/repr-align-assign.rs b/src/test/ui/repr-align-assign.rs
index c9780dde235..3bc3b5c64ce 100644
--- a/src/test/ui/repr-align-assign.rs
+++ b/src/test/ui/repr-align-assign.rs
@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// run-rustfix
+
+#![allow(dead_code)]
+
 #[repr(align=8)] //~ ERROR incorrect `repr(align)` attribute format
 struct A(u64);
 
diff --git a/src/test/ui/repr-align-assign.stderr b/src/test/ui/repr-align-assign.stderr
index 1fa1263b946..c325b6968fe 100644
--- a/src/test/ui/repr-align-assign.stderr
+++ b/src/test/ui/repr-align-assign.stderr
@@ -1,11 +1,11 @@
 error[E0693]: incorrect `repr(align)` attribute format
-  --> $DIR/repr-align-assign.rs:11:8
+  --> $DIR/repr-align-assign.rs:15:8
    |
 LL | #[repr(align=8)] //~ ERROR incorrect `repr(align)` attribute format
    |        ^^^^^^^ help: use parentheses instead: `align(8)`
 
 error[E0693]: incorrect `repr(align)` attribute format
-  --> $DIR/repr-align-assign.rs:14:8
+  --> $DIR/repr-align-assign.rs:18:8
    |
 LL | #[repr(align="8")] //~ ERROR incorrect `repr(align)` attribute format
    |        ^^^^^^^^^ help: use parentheses instead: `align(8)`
diff --git a/src/test/ui/suggestions/issue-32354-suggest-import-rename.fixed b/src/test/ui/suggestions/issue-32354-suggest-import-rename.fixed
new file mode 100644
index 00000000000..251f7eb9a24
--- /dev/null
+++ b/src/test/ui/suggestions/issue-32354-suggest-import-rename.fixed
@@ -0,0 +1,26 @@
+// 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.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+#![allow(unused_imports)]
+
+pub mod extension1 {
+    pub trait ConstructorExtension {}
+}
+
+pub mod extension2 {
+    pub trait ConstructorExtension {}
+}
+
+use extension1::ConstructorExtension;
+use extension2::ConstructorExtension as OtherConstructorExtension; //~ ERROR is defined multiple times
+
+fn main() {}
diff --git a/src/test/ui/suggestions/issue-32354-suggest-import-rename.rs b/src/test/ui/suggestions/issue-32354-suggest-import-rename.rs
index 9d71ab1a788..57cbeb47a1e 100644
--- a/src/test/ui/suggestions/issue-32354-suggest-import-rename.rs
+++ b/src/test/ui/suggestions/issue-32354-suggest-import-rename.rs
@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// run-rustfix
+
+#![allow(unused_imports)]
+
 pub mod extension1 {
     pub trait ConstructorExtension {}
 }
diff --git a/src/test/ui/suggestions/issue-32354-suggest-import-rename.stderr b/src/test/ui/suggestions/issue-32354-suggest-import-rename.stderr
index 7cf7a1d15a2..f45a5f7dd61 100644
--- a/src/test/ui/suggestions/issue-32354-suggest-import-rename.stderr
+++ b/src/test/ui/suggestions/issue-32354-suggest-import-rename.stderr
@@ -1,5 +1,5 @@
 error[E0252]: the name `ConstructorExtension` is defined multiple times
-  --> $DIR/issue-32354-suggest-import-rename.rs:20:5
+  --> $DIR/issue-32354-suggest-import-rename.rs:24:5
    |
 LL | use extension1::ConstructorExtension;
    |     -------------------------------- previous import of the trait `ConstructorExtension` here
diff --git a/src/test/ui/suggestions/pub-ident-fn-or-struct-2.stderr b/src/test/ui/suggestions/pub-ident-fn-or-struct-2.stderr
index c945033ad74..e492a8c4756 100644
--- a/src/test/ui/suggestions/pub-ident-fn-or-struct-2.stderr
+++ b/src/test/ui/suggestions/pub-ident-fn-or-struct-2.stderr
@@ -2,7 +2,7 @@ error: missing `fn` or `struct` for method or struct definition
   --> $DIR/pub-ident-fn-or-struct-2.rs:11:4
    |
 LL | pub S();
-   | ---^- help: if you meant to call a macro, write instead: `S!`
+   | ---^- help: if you meant to call a macro, try: `S!`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/pub-ident-fn-or-struct.stderr b/src/test/ui/suggestions/pub-ident-fn-or-struct.stderr
index 9528c15dfa1..c1bff34cec3 100644
--- a/src/test/ui/suggestions/pub-ident-fn-or-struct.stderr
+++ b/src/test/ui/suggestions/pub-ident-fn-or-struct.stderr
@@ -2,7 +2,7 @@ error: missing `fn` or `struct` for method or struct definition
   --> $DIR/pub-ident-fn-or-struct.rs:11:4
    |
 LL | pub S (foo) bar
-   | ---^- help: if you meant to call a macro, write instead: `S!`
+   | ---^- help: if you meant to call a macro, try: `S!`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/pub-ident-fn.fixed b/src/test/ui/suggestions/pub-ident-fn.fixed
new file mode 100644
index 00000000000..f2d0c6c3e1d
--- /dev/null
+++ b/src/test/ui/suggestions/pub-ident-fn.fixed
@@ -0,0 +1,18 @@
+// 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.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+pub fn foo(_s: usize) -> bool { true }
+//~^ ERROR missing `fn` for method definition
+
+fn main() {
+    foo(2);
+}
diff --git a/src/test/ui/suggestions/pub-ident-fn.rs b/src/test/ui/suggestions/pub-ident-fn.rs
index 1d641996420..82c32f57eea 100644
--- a/src/test/ui/suggestions/pub-ident-fn.rs
+++ b/src/test/ui/suggestions/pub-ident-fn.rs
@@ -8,7 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-pub   foo(s: usize) -> bool { true }
+// run-rustfix
+
+pub   foo(_s: usize) -> bool { true }
 //~^ ERROR missing `fn` for method definition
 
 fn main() {
diff --git a/src/test/ui/suggestions/pub-ident-fn.stderr b/src/test/ui/suggestions/pub-ident-fn.stderr
index de7ee71d1b4..f7c96b8b9f4 100644
--- a/src/test/ui/suggestions/pub-ident-fn.stderr
+++ b/src/test/ui/suggestions/pub-ident-fn.stderr
@@ -1,11 +1,11 @@
 error: missing `fn` for method definition
-  --> $DIR/pub-ident-fn.rs:11:4
+  --> $DIR/pub-ident-fn.rs:13:4
    |
-LL | pub   foo(s: usize) -> bool { true }
+LL | pub   foo(_s: usize) -> bool { true }
    |    ^^^
 help: add `fn` here to parse `foo` as a public method
    |
-LL | pub fn foo(s: usize) -> bool { true }
+LL | pub fn foo(_s: usize) -> bool { true }
    |     ^^
 
 error: aborting due to previous error
diff --git a/src/test/ui/suggestions/type-ascription-instead-of-statement-end.stderr b/src/test/ui/suggestions/type-ascription-instead-of-statement-end.stderr
index 02a80d86c84..314c9060d4f 100644
--- a/src/test/ui/suggestions/type-ascription-instead-of-statement-end.stderr
+++ b/src/test/ui/suggestions/type-ascription-instead-of-statement-end.stderr
@@ -2,7 +2,7 @@ error: expected type, found `0`
   --> $DIR/type-ascription-instead-of-statement-end.rs:15:5
    |
 LL |     println!("test"):
-   |                     - help: did you mean to use `;` here?
+   |                     - help: try using a semicolon: `;`
 LL |     0; //~ ERROR expected type, found `0`
    |     ^ expecting a type here because of type ascription