Rollup merge of #40816 - estebank:issue-38321, r=nikomatsakis

Clarify suggetion for field used as method

Instead of

```rust
error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
    |
note: did you mean to write `self.src_addr`?
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^
```

present

```rust
error: no method named `src_addr` found for type `&wire::ipv4::Repr` in the current scope
   --> src/wire/ipv4.rs:409:34
    |
409 |         packet.set_src_addr(self.src_addr());
    |                                  ^^^^^^^^ field, not a method
    |
    = help: did you mean to write `self.src_addr` instead of `self.src_addr(...)`?
```

Fix #38321.

9 files changed, 186 insertions, 30 deletions

diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index 6ce50d91124..67ee7ef5865 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -197,18 +197,18 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                     let field_ty = field.ty(tcx, substs);
 
                                     if self.is_fn_ty(&field_ty, span) {
-                                        err.span_note(span,
-                                                      &format!("use `({0}.{1})(...)` if you \
-                                                                meant to call the function \
-                                                                stored in the `{1}` field",
-                                                               expr_string,
-                                                               item_name));
+                                        err.help(&format!("use `({0}.{1})(...)` if you \
+                                                           meant to call the function \
+                                                           stored in the `{1}` field",
+                                                          expr_string,
+                                                          item_name));
                                     } else {
-                                        err.span_note(span,
-                                                      &format!("did you mean to write `{0}.{1}`?",
-                                                               expr_string,
-                                                               item_name));
+                                        err.help(&format!("did you mean to write `{0}.{1}` \
+                                                           instead of `{0}.{1}(...)`?",
+                                                          expr_string,
+                                                          item_name));
                                     }
+                                    err.span_label(span, &"field, not a method");
                                     break;
                                 }
                             }
diff --git a/src/test/compile-fail/issue-18343.rs b/src/test/ui/suggestions/confuse-field-and-method/issue-18343.rs
index 4601db9dba0..fc3c58e5223 100644
--- a/src/test/compile-fail/issue-18343.rs
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-18343.rs
@@ -14,6 +14,8 @@ struct Obj<F> where F: FnMut() -> u32 {
 
 fn main() {
     let o = Obj { closure: || 42 };
-    o.closure(); //~ ERROR no method named `closure` found
-    //~^ NOTE use `(o.closure)(...)` if you meant to call the function stored in the `closure` field
+    o.closure();
+    //~^ ERROR no method named `closure` found
+    //~| HELP use `(o.closure)(...)` if you meant to call the function stored in the `closure` field
+    //~| NOTE field, not a method
 }
diff --git a/src/test/ui/suggestions/confuse-field-and-method/issue-18343.stderr b/src/test/ui/suggestions/confuse-field-and-method/issue-18343.stderr
new file mode 100644
index 00000000000..9e5e4adb180
--- /dev/null
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-18343.stderr
@@ -0,0 +1,10 @@
+error: no method named `closure` found for type `Obj<[closure@$DIR/issue-18343.rs:16:28: 16:33]>` in the current scope
+  --> $DIR/issue-18343.rs:17:7
+   |
+17 |     o.closure();
+   |       ^^^^^^^ field, not a method
+   |
+   = help: use `(o.closure)(...)` if you meant to call the function stored in the `closure` field
+
+error: aborting due to previous error
+
diff --git a/src/test/compile-fail/issue-2392.rs b/src/test/ui/suggestions/confuse-field-and-method/issue-2392.rs
index 805725dd749..f84f35ce84b 100644
--- a/src/test/compile-fail/issue-2392.rs
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-2392.rs
@@ -48,45 +48,58 @@ fn main() {
 
     let o_closure = Obj { closure: || 42, not_closure: 42 };
     o_closure.closure(); //~ ERROR no method named `closure` found
-    //~^ NOTE use `(o_closure.closure)(...)` if you meant to call the function stored
+    //~^ HELP use `(o_closure.closure)(...)` if you meant to call the function stored
+    //~| NOTE field, not a method
 
-    o_closure.not_closure(); //~ ERROR no method named `not_closure` found
-    //~^ NOTE did you mean to write `o_closure.not_closure`?
+    o_closure.not_closure();
+    //~^ ERROR no method named `not_closure` found
+    //~| NOTE field, not a method
+    //~| HELP did you mean to write `o_closure.not_closure` instead of `o_closure.not_closure(...)`?
 
     let o_func = Obj { closure: func, not_closure: 5 };
     o_func.closure(); //~ ERROR no method named `closure` found
-    //~^ NOTE use `(o_func.closure)(...)` if you meant to call the function stored
+    //~^ HELP use `(o_func.closure)(...)` if you meant to call the function stored
+    //~| NOTE field, not a method
 
     let boxed_fn = BoxedObj { boxed_closure: Box::new(func) };
     boxed_fn.boxed_closure();//~ ERROR no method named `boxed_closure` found
-    //~^ NOTE use `(boxed_fn.boxed_closure)(...)` if you meant to call the function stored
+    //~^ HELP use `(boxed_fn.boxed_closure)(...)` if you meant to call the function stored
+    //~| NOTE field, not a method
 
     let boxed_closure = BoxedObj { boxed_closure: Box::new(|| 42_u32) as Box<FnBox() -> u32> };
     boxed_closure.boxed_closure();//~ ERROR no method named `boxed_closure` found
-    //~^ NOTE use `(boxed_closure.boxed_closure)(...)` if you meant to call the function stored
+    //~^ HELP use `(boxed_closure.boxed_closure)(...)` if you meant to call the function stored
+    //~| NOTE field, not a method
 
     // test expression writing in the notes
 
     let w = Wrapper { wrap: o_func };
     w.wrap.closure();//~ ERROR no method named `closure` found
-    //~^ NOTE use `(w.wrap.closure)(...)` if you meant to call the function stored
+    //~^ HELP use `(w.wrap.closure)(...)` if you meant to call the function stored
+    //~| NOTE field, not a method
 
-    w.wrap.not_closure();//~ ERROR no method named `not_closure` found
-    //~^ NOTE did you mean to write `w.wrap.not_closure`?
+    w.wrap.not_closure();
+    //~^ ERROR no method named `not_closure` found
+    //~| NOTE field, not a method
+    //~| HELP did you mean to write `w.wrap.not_closure` instead of `w.wrap.not_closure(...)`?
 
     check_expression().closure();//~ ERROR no method named `closure` found
-    //~^ NOTE use `(check_expression().closure)(...)` if you meant to call the function stored
+    //~^ HELP use `(check_expression().closure)(...)` if you meant to call the function stored
+    //~| NOTE field, not a method
 }
 
 impl FuncContainerOuter {
     fn run(&self) {
         unsafe {
             (*self.container).f1(1); //~ ERROR no method named `f1` found
-            //~^ NOTE use `((*self.container).f1)(...)`
+            //~^ HELP use `((*self.container).f1)(...)`
+            //~| NOTE field, not a method
             (*self.container).f2(1); //~ ERROR no method named `f2` found
-            //~^ NOTE use `((*self.container).f2)(...)`
+            //~^ HELP use `((*self.container).f2)(...)`
+            //~| NOTE field, not a method
             (*self.container).f3(1); //~ ERROR no method named `f3` found
-            //~^ NOTE use `((*self.container).f3)(...)`
+            //~^ HELP use `((*self.container).f3)(...)`
+            //~| NOTE field, not a method
         }
     }
 }
diff --git a/src/test/ui/suggestions/confuse-field-and-method/issue-2392.stderr b/src/test/ui/suggestions/confuse-field-and-method/issue-2392.stderr
new file mode 100644
index 00000000000..56e1060bdb9
--- /dev/null
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-2392.stderr
@@ -0,0 +1,90 @@
+error: no method named `closure` found for type `Obj<[closure@$DIR/issue-2392.rs:49:36: 49:41]>` in the current scope
+  --> $DIR/issue-2392.rs:50:15
+   |
+50 |     o_closure.closure(); //~ ERROR no method named `closure` found
+   |               ^^^^^^^ field, not a method
+   |
+   = help: use `(o_closure.closure)(...)` if you meant to call the function stored in the `closure` field
+
+error: no method named `not_closure` found for type `Obj<[closure@$DIR/issue-2392.rs:49:36: 49:41]>` in the current scope
+  --> $DIR/issue-2392.rs:54:15
+   |
+54 |     o_closure.not_closure();
+   |               ^^^^^^^^^^^ field, not a method
+   |
+   = help: did you mean to write `o_closure.not_closure` instead of `o_closure.not_closure(...)`?
+
+error: no method named `closure` found for type `Obj<fn() -> u32 {func}>` in the current scope
+  --> $DIR/issue-2392.rs:60:12
+   |
+60 |     o_func.closure(); //~ ERROR no method named `closure` found
+   |            ^^^^^^^ field, not a method
+   |
+   = help: use `(o_func.closure)(...)` if you meant to call the function stored in the `closure` field
+
+error: no method named `boxed_closure` found for type `BoxedObj` in the current scope
+  --> $DIR/issue-2392.rs:65:14
+   |
+65 |     boxed_fn.boxed_closure();//~ ERROR no method named `boxed_closure` found
+   |              ^^^^^^^^^^^^^ field, not a method
+   |
+   = help: use `(boxed_fn.boxed_closure)(...)` if you meant to call the function stored in the `boxed_closure` field
+
+error: no method named `boxed_closure` found for type `BoxedObj` in the current scope
+  --> $DIR/issue-2392.rs:70:19
+   |
+70 |     boxed_closure.boxed_closure();//~ ERROR no method named `boxed_closure` found
+   |                   ^^^^^^^^^^^^^ field, not a method
+   |
+   = help: use `(boxed_closure.boxed_closure)(...)` if you meant to call the function stored in the `boxed_closure` field
+
+error: no method named `closure` found for type `Obj<fn() -> u32 {func}>` in the current scope
+  --> $DIR/issue-2392.rs:77:12
+   |
+77 |     w.wrap.closure();//~ ERROR no method named `closure` found
+   |            ^^^^^^^ field, not a method
+   |
+   = help: use `(w.wrap.closure)(...)` if you meant to call the function stored in the `closure` field
+
+error: no method named `not_closure` found for type `Obj<fn() -> u32 {func}>` in the current scope
+  --> $DIR/issue-2392.rs:81:12
+   |
+81 |     w.wrap.not_closure();
+   |            ^^^^^^^^^^^ field, not a method
+   |
+   = help: did you mean to write `w.wrap.not_closure` instead of `w.wrap.not_closure(...)`?
+
+error: no method named `closure` found for type `Obj<std::boxed::Box<std::boxed::FnBox<(), Output=u32> + 'static>>` in the current scope
+  --> $DIR/issue-2392.rs:86:24
+   |
+86 |     check_expression().closure();//~ ERROR no method named `closure` found
+   |                        ^^^^^^^ field, not a method
+   |
+   = help: use `(check_expression().closure)(...)` if you meant to call the function stored in the `closure` field
+
+error: no method named `f1` found for type `FuncContainer` in the current scope
+  --> $DIR/issue-2392.rs:94:31
+   |
+94 |             (*self.container).f1(1); //~ ERROR no method named `f1` found
+   |                               ^^ field, not a method
+   |
+   = help: use `((*self.container).f1)(...)` if you meant to call the function stored in the `f1` field
+
+error: no method named `f2` found for type `FuncContainer` in the current scope
+  --> $DIR/issue-2392.rs:97:31
+   |
+97 |             (*self.container).f2(1); //~ ERROR no method named `f2` found
+   |                               ^^ field, not a method
+   |
+   = help: use `((*self.container).f2)(...)` if you meant to call the function stored in the `f2` field
+
+error: no method named `f3` found for type `FuncContainer` in the current scope
+   --> $DIR/issue-2392.rs:100:31
+    |
+100 |             (*self.container).f3(1); //~ ERROR no method named `f3` found
+    |                               ^^ field, not a method
+    |
+    = help: use `((*self.container).f3)(...)` if you meant to call the function stored in the `f3` field
+
+error: aborting due to 11 previous errors
+
diff --git a/src/test/compile-fail/issue-32128.rs b/src/test/ui/suggestions/confuse-field-and-method/issue-32128.rs
index fe7e66a2116..2fd7dc246c2 100644
--- a/src/test/compile-fail/issue-32128.rs
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-32128.rs
@@ -19,7 +19,9 @@ fn main() {
         })
     };
 
-    demo.example(1);    //~ ERROR no method named `example`
-                        //~^ NOTE use `(demo.example)(...)`
+    demo.example(1);
+    //~^ ERROR no method named `example`
+    //~| HELP use `(demo.example)(...)`
+    //~| NOTE field, not a method
     // (demo.example)(1);
 }
diff --git a/src/test/ui/suggestions/confuse-field-and-method/issue-32128.stderr b/src/test/ui/suggestions/confuse-field-and-method/issue-32128.stderr
new file mode 100644
index 00000000000..0d2a895bad1
--- /dev/null
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-32128.stderr
@@ -0,0 +1,10 @@
+error: no method named `example` found for type `Example` in the current scope
+  --> $DIR/issue-32128.rs:22:10
+   |
+22 |     demo.example(1);
+   |          ^^^^^^^ field, not a method
+   |
+   = help: use `(demo.example)(...)` if you meant to call the function stored in the `example` field
+
+error: aborting due to previous error
+
diff --git a/src/test/compile-fail/issue-33784.rs b/src/test/ui/suggestions/confuse-field-and-method/issue-33784.rs
index 4229be29473..03c84fc57be 100644
--- a/src/test/compile-fail/issue-33784.rs
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-33784.rs
@@ -35,12 +35,15 @@ fn main() {
     let o = Obj { fn_ptr: empty, closure: || 42 };
     let p = &o;
     p.closure(); //~ ERROR no method named `closure` found
-    //~^ NOTE use `(p.closure)(...)` if you meant to call the function stored in the `closure` field
+    //~^ HELP use `(p.closure)(...)` if you meant to call the function stored in the `closure` field
+    //~| NOTE `closure` is a field storing a function, not a method
     let q = &p;
     q.fn_ptr(); //~ ERROR no method named `fn_ptr` found
-    //~^ NOTE use `(q.fn_ptr)(...)` if you meant to call the function stored in the `fn_ptr` field
+    //~^ HELP use `(q.fn_ptr)(...)` if you meant to call the function stored in the `fn_ptr` field
+    //~| NOTE `fn_ptr` is a field storing a function, not a method
     let r = D(C { c_fn_ptr: empty });
     let s = &r;
     s.c_fn_ptr(); //~ ERROR no method named `c_fn_ptr` found
-    //~^ NOTE use `(s.c_fn_ptr)(...)` if you meant to call the function stored in the `c_fn_ptr`
+    //~^ HELP use `(s.c_fn_ptr)(...)` if you meant to call the function stored in the `c_fn_ptr`
+    //~| NOTE `c_fn_ptr` is a field storing a function, not a method
 }
diff --git a/src/test/ui/suggestions/confuse-field-and-method/issue-33784.stderr b/src/test/ui/suggestions/confuse-field-and-method/issue-33784.stderr
new file mode 100644
index 00000000000..70d64e3ffa3
--- /dev/null
+++ b/src/test/ui/suggestions/confuse-field-and-method/issue-33784.stderr
@@ -0,0 +1,26 @@
+error: no method named `closure` found for type `&Obj<[closure@$DIR/issue-33784.rs:35:43: 35:48]>` in the current scope
+  --> $DIR/issue-33784.rs:37:7
+   |
+37 |     p.closure(); //~ ERROR no method named `closure` found
+   |       ^^^^^^^ field, not a method
+   |
+   = help: use `(p.closure)(...)` if you meant to call the function stored in the `closure` field
+
+error: no method named `fn_ptr` found for type `&&Obj<[closure@$DIR/issue-33784.rs:35:43: 35:48]>` in the current scope
+  --> $DIR/issue-33784.rs:41:7
+   |
+41 |     q.fn_ptr(); //~ ERROR no method named `fn_ptr` found
+   |       ^^^^^^ field, not a method
+   |
+   = help: use `(q.fn_ptr)(...)` if you meant to call the function stored in the `fn_ptr` field
+
+error: no method named `c_fn_ptr` found for type `&D` in the current scope
+  --> $DIR/issue-33784.rs:46:7
+   |
+46 |     s.c_fn_ptr(); //~ ERROR no method named `c_fn_ptr` found
+   |       ^^^^^^^^ field, not a method
+   |
+   = help: use `(s.c_fn_ptr)(...)` if you meant to call the function stored in the `c_fn_ptr` field
+
+error: aborting due to 3 previous errors
+