Rollup merge of #36798 - gavinb:fix/36164, r=GuillaumeGomez

Improve error message and snippet for "did you mean `x`"

- Fixes #36164
- Part of #35233

Based on the standalone example https://is.gd/8STXMd posted by @nikomatsakis and using the third formatting option mentioned in #36164 and agreed by @jonathandturner.

Note however this does not address the question of [how to handle an empty or unknown suggestion](https://github.com/rust-lang/rust/issues/36164#issuecomment-244460024). @nikomatsakis any suggestions on how best to address that part?

src/librustc_typeck/check/mod.rs

@@ -2959,18 +2959,20 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 .emit();
             self.tcx().types.err
         } else {
-            let mut err = self.type_error_struct(expr.span, |actual| {
-                format!("attempted access of field `{}` on type `{}`, \
-                         but no field with that name was found",
+            let mut err = self.type_error_struct(field.span, |actual| {
+                format!("no field `{}` on type `{}`",
                         field.node, actual)
             }, expr_t);
             match expr_t.sty {
                 ty::TyAdt(def, _) if !def.is_enum() => {
                     if let Some(suggested_field_name) =
                         Self::suggest_field_name(def.struct_variant(), field, vec![]) {
-                        err.span_help(field.span,
-                                      &format!("did you mean `{}`?", suggested_field_name));
-                    };
+                            err.span_label(field.span,
+                                           &format!("did you mean `{}`?", suggested_field_name));
+                        } else {
+                            err.span_label(field.span,
+                                           &format!("unknown field"));
+                        };
                 }
                 ty::TyRawPtr(..) => {
                     err.note(&format!("`{0}` is a native pointer; perhaps you need to deref with \

src/test/compile-fail/attempted-access-non-fatal.rs

@@ -11,6 +11,6 @@
 // Check that bogus field access is non-fatal
 fn main() {
     let x = 0;
-    let _ = x.foo; //~ ERROR attempted access of field
-    let _ = x.bar; //~ ERROR attempted access of field
+    let _ = x.foo; //~ no field `foo` on type `{integer}`
+    let _ = x.bar; //~ no field `bar` on type `{integer}`
 }

src/test/compile-fail/cast-rfc0401.rs

@@ -112,7 +112,7 @@ fn main()
     //~| NOTE required for the cast to the object type `Foo`
 
     // check no error cascade
-    let _ = main.f as *const u32; //~ ERROR attempted access of field
+    let _ = main.f as *const u32; //~ no field `f` on type `fn() {main}`
 
     let cf: *const Foo = &0;
     let _ = cf as *const [u16];

src/test/compile-fail/derived-errors/issue-30580.rs

@@ -19,7 +19,7 @@ impl<'a, 'tcx> Pass<'a, 'tcx>
     pub fn tcx(&self) -> &'a &'tcx () { self.1 }
     fn lol(&mut self, b: &Foo)
     {
-        b.c; //~ ERROR no field with that name was found
+        b.c; //~ ERROR no field `c` on type `&Foo`
         self.tcx();
     }
 }

src/test/compile-fail/issue-11004.rs

@@ -14,9 +14,9 @@ struct A { x: i32, y: f64 }
 
 #[cfg(not(works))]
 unsafe fn access(n:*mut A) -> (i32, f64) {
-    let x : i32 = n.x; //~ ERROR attempted access of field `x`
+    let x : i32 = n.x; //~ no field `x` on type `*mut A`
                        //~| NOTE `n` is a native pointer; perhaps you need to deref with `(*n).x`
-    let y : f64 = n.y; //~ ERROR attempted access of field `y`
+    let y : f64 = n.y; //~ no field `y` on type `*mut A`
                        //~| NOTE `n` is a native pointer; perhaps you need to deref with `(*n).y`
     (x, y)
 }

src/test/compile-fail/issue-14721.rs

@@ -10,6 +10,5 @@
 
 fn main() {
     let foo = "str";
-    println!("{}", foo.desc); //~ ERROR attempted access of field `desc` on type `&str`,
-                              //        but no field with that name was found
+    println!("{}", foo.desc); //~ no field `desc` on type `&str`
 }

src/test/compile-fail/issue-19244-2.rs

@@ -13,5 +13,5 @@ const STRUCT: MyStruct = MyStruct { field: 42 };
 
 fn main() {
     let a: [isize; STRUCT.nonexistent_field];
-    //~^ ERROR attempted access of field `nonexistent_field`
+    //~^ no field `nonexistent_field` on type `MyStruct`
 }

src/test/compile-fail/issue-23253.rs

@@ -12,5 +12,5 @@ enum Foo { Bar }
 
 fn main() {
     Foo::Bar.a;
-    //~^ ERROR: attempted access of field `a` on type `Foo`, but no field with that name was found
+    //~^ no field `a` on type `Foo`
 }

src/test/compile-fail/issue-24363.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 fn main() {
-    1.create_a_type_error[ //~ ERROR attempted access of field
+    1.create_a_type_error[ //~ no field `create_a_type_error` on type `{integer}`
         ()+() //~ ERROR binary operation `+` cannot be applied
               //   ^ ensure that we typeck the inner expression ^
     ];

src/test/compile-fail/issue-24365.rs

@@ -17,13 +17,13 @@ pub enum Foo {
 }
 
 fn test(a: Foo) {
-    println!("{}", a.b); //~ ERROR attempted access of field
+    println!("{}", a.b); //~ no field `b` on type `Foo`
 }
 
 fn main() {
     let x = Attribute::Code {
         attr_name_idx: 42,
     };
-    let z = (&x).attr_name_idx; //~ ERROR attempted access of field
-    let y = x.attr_name_idx; //~ ERROR attempted access of field
+    let z = (&x).attr_name_idx; //~ no field `attr_name_idx` on type `&Attribute`
+    let y = x.attr_name_idx; //~ no field `attr_name_idx` on type `Attribute`
 }

src/test/compile-fail/issue-31011.rs

@@ -11,7 +11,7 @@
 macro_rules! log {
     ( $ctx:expr, $( $args:expr),* ) => {
         if $ctx.trace {
-        //~^ ERROR attempted access of field `trace` on type `&T`, but no field with that name
+        //~^ no field `trace` on type `&T`
             println!( $( $args, )* );
         }
     }

src/test/compile-fail/no-type-for-node-ice.rs

@@ -11,5 +11,5 @@
 // Related issues: #20401, #20506, #20614, #20752, #20829, #20846, #20885, #20886
 
 fn main() {
-    "".homura[""]; //~ ERROR no field with that name was found
+    "".homura[""]; //~ no field `homura` on type `&'static str`
 }

src/test/compile-fail/struct-fields-typo.rs

@@ -18,7 +18,7 @@ fn main() {
         foo: 0,
         bar: 0.5,
     };
-    let x = foo.baa;//~ ERROR attempted access of field `baa` on type `BuildData`
-    //~^ HELP did you mean `bar`?
+    let x = foo.baa;//~ no field `baa` on type `BuildData`
+    //~^ did you mean `bar`?
     println!("{}", x);
 }

src/test/compile-fail/struct-pat-derived-error.rs

@@ -15,7 +15,7 @@ struct a {
 
 impl a {
     fn foo(&self) {
-        let a { x, y } = self.d; //~ ERROR attempted access of field `d`
+        let a { x, y } = self.d; //~ ERROR no field `d` on type `&a`
         //~^ ERROR struct `a` does not have a field named `x`
         //~^^ ERROR struct `a` does not have a field named `y`
         //~^^^ ERROR pattern does not mention field `b`

src/test/compile-fail/union/union-suggest-field.rs

@@ -22,8 +22,8 @@ fn main() {
     let u = U { principle: 0 };
     //~^ ERROR union `U` has no field named `principle`
     //~| NOTE field does not exist - did you mean `principal`?
-    let w = u.principial; //~ ERROR attempted access of field `principial` on type `U`
-                          //~^ HELP did you mean `principal`?
+    let w = u.principial; //~ ERROR no field `principial` on type `U`
+                          //~^ did you mean `principal`?
 
     let y = u.calculate; //~ ERROR attempted to take value of method `calculate` on type `U`
                          //~^ HELP maybe a `()` to call it is missing?

src/test/compile-fail/unsafe-fn-autoderef.rs

@@ -26,7 +26,7 @@ fn f(p: *const Rec) -> isize {
     // are prohibited by various checks, such as that the enum is
     // instantiable and so forth).
 
-    return p.f; //~ ERROR attempted access of field `f` on type `*const Rec`
+    return p.f; //~ ERROR no field `f` on type `*const Rec`
 }
 
 fn main() {

src/test/incremental/struct_change_field_name.rs

@@ -39,13 +39,13 @@ pub fn use_X() -> u32 {
     let x: X = X { x: 22 };
     //[cfail2]~^ ERROR struct `X` has no field named `x`
     x.x as u32
-    //[cfail2]~^ ERROR attempted access of field `x`
+    //[cfail2]~^ ERROR no field `x` on type `X`
 }
 
 #[rustc_dirty(label="TypeckItemBody", cfg="cfail2")]
 pub fn use_EmbedX(embed: EmbedX) -> u32 {
     embed.x.x as u32
-    //[cfail2]~^ ERROR attempted access of field `x`
+    //[cfail2]~^ ERROR no field `x` on type `X`
 }
 
 #[rustc_clean(label="TypeckItemBody", cfg="cfail2")]

src/test/ui/did_you_mean/issue-36798.rs

@@ -0,0 +1,18 @@
+// 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.
+
+struct Foo {
+    bar: u8
+}
+
+fn main() {
+    let f = Foo { bar: 22 };
+    f.baz;
+}

src/test/ui/did_you_mean/issue-36798.stderr

@@ -0,0 +1,8 @@
+error: no field `baz` on type `Foo`
+  --> $DIR/issue-36798.rs:17:7
+   |
+17 |     f.baz;
+   |       ^^^ did you mean `bar`?
+
+error: aborting due to previous error
+

src/test/ui/did_you_mean/issue-36798_unknown_field.rs

@@ -0,0 +1,18 @@
+// 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.
+
+struct Foo {
+    bar: u8
+}
+
+fn main() {
+    let f = Foo { bar: 22 };
+    f.zz;
+}

src/test/ui/did_you_mean/issue-36798_unknown_field.stderr

@@ -0,0 +1,8 @@
+error: no field `zz` on type `Foo`
+  --> $DIR/issue-36798_unknown_field.rs:17:7
+   |
+17 |     f.zz;
+   |       ^^ unknown field
+
+error: aborting due to previous error
+

src/test/ui/macros/macro-backtrace-invalid-internals.stderr

@@ -7,11 +7,11 @@ error: no method named `fake` found for type `{integer}` in the current scope
 50 |     fake_method_stmt!();
    |     -------------------- in this macro invocation
 
-error: attempted access of field `fake` on type `{integer}`, but no field with that name was found
-  --> $DIR/macro-backtrace-invalid-internals.rs:21:11
+error: no field `fake` on type `{integer}`
+  --> $DIR/macro-backtrace-invalid-internals.rs:21:13
    |
 21 |           1.fake
-   |           ^^^^^^
+   |             ^^^^
 ...
 51 |     fake_field_stmt!();
    |     ------------------- in this macro invocation
@@ -34,11 +34,11 @@ error: no method named `fake` found for type `{integer}` in the current scope
 54 |     let _ = fake_method_expr!();
    |             ------------------- in this macro invocation
 
-error: attempted access of field `fake` on type `{integer}`, but no field with that name was found
-  --> $DIR/macro-backtrace-invalid-internals.rs:39:11
+error: no field `fake` on type `{integer}`
+  --> $DIR/macro-backtrace-invalid-internals.rs:39:13
    |
 39 |           1.fake
-   |           ^^^^^^
+   |             ^^^^
 ...
 55 |     let _ = fake_field_expr!();
    |             ------------------ in this macro invocation