Auto merge of #47116 - estebank:non-accessible-ctor, r=petrochenkov

Tweaks to invalid ctor messages

 - Do not suggest using a constructor that isn't accessible
 - Suggest the appropriate syntax (`()`/`{}` as appropriate)
 - Add note when trying to use `Self` as a ctor

CC #22488, fix #47085.

src/librustc_resolve/lib.rs

@@ -898,7 +898,7 @@ impl<'a> LexicalScopeBinding<'a> {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 enum PathResult<'a> {
     Module(Module<'a>),
     NonModule(PathResolution),
@@ -2568,7 +2568,8 @@ impl<'a> Resolver<'a> {
             let code = source.error_code(def.is_some());
             let (base_msg, fallback_label, base_span) = if let Some(def) = def {
                 (format!("expected {}, found {} `{}`", expected, def.kind_name(), path_str),
-                 format!("not a {}", expected), span)
+                 format!("not a {}", expected),
+                 span)
             } else {
                 let item_str = path[path.len() - 1].node;
                 let item_span = path[path.len() - 1].span;
@@ -2585,7 +2586,8 @@ impl<'a> Resolver<'a> {
                     (mod_prefix, format!("`{}`", names_to_string(mod_path)))
                 };
                 (format!("cannot find {} `{}` in {}{}", expected, item_str, mod_prefix, mod_str),
-                 format!("not found in {}", mod_str), item_span)
+                 format!("not found in {}", mod_str),
+                 item_span)
             };
             let code = DiagnosticId::Error(code.into());
             let mut err = this.session.struct_span_err_with_code(base_span, &base_msg, code);
@@ -2700,20 +2702,37 @@ impl<'a> Resolver<'a> {
                         }
                         return (err, candidates);
                     },
-                    _ if ns == ValueNS && is_struct_like(def) => {
-                        if let Def::Struct(def_id) = def {
-                            if let Some((ctor_def, ctor_vis))
-                                    = this.struct_constructors.get(&def_id).cloned() {
-                                if is_expected(ctor_def) && !this.is_accessible(ctor_vis) {
-                                    err.span_label(span, format!("constructor is not visible \
-                                                                   here due to private fields"));
-                                }
+                    (Def::Struct(def_id), _) if ns == ValueNS => {
+                        if let Some((ctor_def, ctor_vis))
+                                = this.struct_constructors.get(&def_id).cloned() {
+                            let accessible_ctor = this.is_accessible(ctor_vis);
+                            if is_expected(ctor_def) && !accessible_ctor {
+                                err.span_label(span, format!("constructor is not visible \
+                                                              here due to private fields"));
                             }
+                        } else {
+                            err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
+                                                         path_str));
                         }
+                        return (err, candidates);
+                    }
+                    (Def::Union(..), _) |
+                    (Def::Variant(..), _) |
+                    (Def::VariantCtor(_, CtorKind::Fictive), _) if ns == ValueNS => {
                         err.span_label(span, format!("did you mean `{} {{ /* fields */ }}`?",
                                                      path_str));
                         return (err, candidates);
                     }
+                    (Def::SelfTy(..), _) if ns == ValueNS => {
+                        err.span_label(span, fallback_label);
+                        err.note("can't use `Self` as a constructor, you must use the \
+                                  implemented struct");
+                        return (err, candidates);
+                    }
+                    (Def::TyAlias(_), _) | (Def::AssociatedTy(..), _) if ns == ValueNS => {
+                        err.note("can't use a type alias as a constructor");
+                        return (err, candidates);
+                    }
                     _ => {}
                 }
             }
@@ -3965,13 +3984,6 @@ impl<'a> Resolver<'a> {
     }
 }
 
-fn is_struct_like(def: Def) -> bool {
-    match def {
-        Def::VariantCtor(_, CtorKind::Fictive) => true,
-        _ => PathSource::Struct.is_expected(def),
-    }
-}
-
 fn is_self_type(path: &[SpannedIdent], namespace: Namespace) -> bool {
     namespace == TypeNS && path.len() == 1 && path[0].node.name == keywords::SelfType.name()
 }

src/librustc_typeck/check/callee.rs

@@ -210,15 +210,25 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         }
                     }
                 }
-                let mut err = type_error_struct!(self.tcx.sess, call_expr.span, callee_ty, E0618,
-                                                 "expected function, found `{}`",
-                                                 if let Some(ref path) = unit_variant {
-                                                     path.to_string()
-                                                 } else {
-                                                     callee_ty.to_string()
-                                                 });
-                if let Some(path) = unit_variant {
-                    err.help(&format!("did you mean to write `{}`?", path));
+
+                let mut err = type_error_struct!(
+                    self.tcx.sess,
+                    call_expr.span,
+                    callee_ty,
+                    E0618,
+                    "expected function, found {}",
+                    match unit_variant {
+                        Some(ref path) => format!("enum variant `{}`", path),
+                        None => format!("`{}`", callee_ty),
+                    });
+
+                err.span_label(call_expr.span, "not a function");
+
+                if let Some(ref path) = unit_variant {
+                    err.span_suggestion(call_expr.span,
+                                        &format!("`{}` is a unit variant, you need to write it \
+                                                  without the parenthesis", path),
+                                        path.to_string());
                 }
 
                 if let hir::ExprCall(ref expr, _) = call_expr.node {
@@ -235,7 +245,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         _ => self.tcx.hir.span_if_local(def.def_id())
                     };
                     if let Some(span) = def_span {
-                        err.span_note(span, "defined here");
+                        let name = match unit_variant {
+                            Some(path) => path,
+                            None => callee_ty.to_string(),
+                        };
+                        err.span_label(span, format!("`{}` defined here", name));
                     }
                 }
 

src/librustc_typeck/check/compare_method.rs

@@ -518,7 +518,10 @@ fn compare_self_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                            self_descr);
             err.span_label(impl_m_span, format!("`{}` used in impl", self_descr));
             if let Some(span) = tcx.hir.span_if_local(trait_m.def_id) {
-                err.span_label(span, format!("trait declared without `{}`", self_descr));
+                err.span_label(span, format!("trait method declared without `{}`", self_descr));
+            } else {
+                err.note_trait_signature(trait_m.name.to_string(),
+                                         trait_m.signature(&tcx));
             }
             err.emit();
             return Err(ErrorReported);
@@ -533,8 +536,7 @@ fn compare_self_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                             not in the impl",
                                            trait_m.name,
                                            self_descr);
-            err.span_label(impl_m_span,
-                           format!("expected `{}` in impl", self_descr));
+            err.span_label(impl_m_span, format!("expected `{}` in impl", self_descr));
             if let Some(span) = tcx.hir.span_if_local(trait_m.def_id) {
                 err.span_label(span, format!("`{}` used in trait", self_descr));
             } else {

src/test/compile-fail/E0185.rs

@@ -9,14 +9,16 @@
 // except according to those terms.
 
 trait Foo {
-    fn foo(); //~ trait declared without `&self`
+    fn foo();
+    //~^ NOTE trait method declared without `&self`
 }
 
 struct Bar;
 
 impl Foo for Bar {
-    fn foo(&self) {} //~ ERROR E0185
-    //~^ `&self` used in impl
+    fn foo(&self) {}
+    //~^ ERROR E0185
+    //~| NOTE `&self` used in impl
 }
 
 fn main() {

src/test/compile-fail/E0618.rs

@@ -13,7 +13,9 @@ enum X {
 }
 
 fn main() {
-    X::Entry(); //~ ERROR expected function, found `X::Entry` [E0618]
+    X::Entry();
+    //~^ ERROR expected function, found enum variant `X::Entry` [E0618]
     let x = 0i32;
-    x(); //~ ERROR expected function, found `i32` [E0618]
+    x();
+    //~^ ERROR expected function, found `i32` [E0618]
 }

src/test/ui/block-result/issue-20862.stderr

@@ -13,7 +13,7 @@ error[E0618]: expected function, found `()`
   --> $DIR/issue-20862.rs:17:13
    |
 17 |     let x = foo(5)(2);
-   |             ^^^^^^^^^
+   |             ^^^^^^^^^ not a function
 
 error: aborting due to 2 previous errors
 

src/test/ui/empty-struct-unit-expr.rs

@@ -24,8 +24,8 @@ enum E {
 fn main() {
     let e2 = Empty2(); //~ ERROR expected function, found `Empty2`
     let e4 = E::Empty4();
-    //~^ ERROR expected function, found `E::Empty4` [E0618]
+    //~^ ERROR expected function, found enum variant `E::Empty4` [E0618]
     let xe2 = XEmpty2(); //~ ERROR expected function, found `empty_struct::XEmpty2`
     let xe4 = XE::XEmpty4();
-    //~^ ERROR expected function, found `XE::XEmpty4` [E0618]
+    //~^ ERROR expected function, found enum variant `XE::XEmpty4` [E0618]
 }

src/test/ui/empty-struct-unit-expr.stderr

@@ -1,41 +1,40 @@
 error[E0618]: expected function, found `Empty2`
   --> $DIR/empty-struct-unit-expr.rs:25:14
    |
-25 |     let e2 = Empty2(); //~ ERROR expected function, found `Empty2`
-   |              ^^^^^^^^
-   |
-note: defined here
-  --> $DIR/empty-struct-unit-expr.rs:18:1
-   |
 18 | struct Empty2;
-   | ^^^^^^^^^^^^^^
+   | -------------- `Empty2` defined here
+...
+25 |     let e2 = Empty2(); //~ ERROR expected function, found `Empty2`
+   |              ^^^^^^^^ not a function
 
-error[E0618]: expected function, found `E::Empty4`
+error[E0618]: expected function, found enum variant `E::Empty4`
   --> $DIR/empty-struct-unit-expr.rs:26:14
    |
+21 |     Empty4
+   |     ------ `E::Empty4` defined here
+...
 26 |     let e4 = E::Empty4();
-   |              ^^^^^^^^^^^
-   |
-   = help: did you mean to write `E::Empty4`?
-note: defined here
-  --> $DIR/empty-struct-unit-expr.rs:21:5
+   |              ^^^^^^^^^^^ not a function
+help: `E::Empty4` is a unit variant, you need to write it without the parenthesis
    |
-21 |     Empty4
-   |     ^^^^^^
+26 |     let e4 = E::Empty4;
+   |              ^^^^^^^^^
 
 error[E0618]: expected function, found `empty_struct::XEmpty2`
   --> $DIR/empty-struct-unit-expr.rs:28:15
    |
 28 |     let xe2 = XEmpty2(); //~ ERROR expected function, found `empty_struct::XEmpty2`
-   |               ^^^^^^^^^
+   |               ^^^^^^^^^ not a function
 
-error[E0618]: expected function, found `XE::XEmpty4`
+error[E0618]: expected function, found enum variant `XE::XEmpty4`
   --> $DIR/empty-struct-unit-expr.rs:29:15
    |
 29 |     let xe4 = XE::XEmpty4();
-   |               ^^^^^^^^^^^^^
+   |               ^^^^^^^^^^^^^ not a function
+help: `XE::XEmpty4` is a unit variant, you need to write it without the parenthesis
    |
-   = help: did you mean to write `XE::XEmpty4`?
+29 |     let xe4 = XE::XEmpty4;
+   |               ^^^^^^^^^^^
 
 error: aborting due to 4 previous errors
 

src/test/ui/issue-10969.stderr

@@ -1,26 +1,18 @@
 error[E0618]: expected function, found `i32`
   --> $DIR/issue-10969.rs:12:5
    |
-12 |     i(); //~ERROR expected function, found `i32`
-   |     ^^^
-   |
-note: defined here
-  --> $DIR/issue-10969.rs:11:9
-   |
 11 | fn func(i: i32) {
-   |         ^
+   |         - `i32` defined here
+12 |     i(); //~ERROR expected function, found `i32`
+   |     ^^^ not a function
 
 error[E0618]: expected function, found `i32`
   --> $DIR/issue-10969.rs:16:5
    |
-16 |     i(); //~ERROR expected function, found `i32`
-   |     ^^^
-   |
-note: defined here
-  --> $DIR/issue-10969.rs:15:9
-   |
 15 |     let i = 0i32;
-   |         ^
+   |         - `i32` defined here
+16 |     i(); //~ERROR expected function, found `i32`
+   |     ^^^ not a function
 
 error: aborting due to 2 previous errors
 

src/test/ui/resolve/privacy-enum-ctor.rs

@@ -0,0 +1,81 @@
+// 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.
+
+mod m {
+    pub enum E {
+        Fn(u8),
+        Struct {
+            s: u8,
+        },
+        Unit,
+    }
+
+    pub mod n {
+        pub(in m) enum Z {
+            Fn(u8),
+            Struct {
+                s: u8,
+            },
+            Unit,
+        }
+    }
+
+    use m::n::Z; // OK, only the type is imported
+
+    fn f() {
+        n::Z;
+        //~^ ERROR expected value, found enum `n::Z`
+        Z;
+        //~^ ERROR expected value, found enum `Z`
+        let _: Z = Z::Fn;
+        //~^ ERROR mismatched types
+        let _: Z = Z::Struct;
+        //~^ ERROR expected value, found struct variant `Z::Struct`
+        let _ = Z::Unit();
+        //~^ ERROR expected function, found enum variant `Z::Unit`
+        let _ = Z::Unit {};
+        // This is ok, it is equivalent to not having braces
+    }
+}
+
+use m::E; // OK, only the type is imported
+
+fn main() {
+    let _: E = m::E;
+    //~^ ERROR expected value, found enum `m::E`
+    let _: E = m::E::Fn;
+    //~^ ERROR mismatched types
+    let _: E = m::E::Struct;
+    //~^ ERROR expected value, found struct variant `m::E::Struct`
+    let _: E = m::E::Unit();
+    //~^ ERROR expected function, found enum variant `m::E::Unit`
+    let _: E = E;
+    //~^ ERROR expected value, found enum `E`
+    let _: E = E::Fn;
+    //~^ ERROR mismatched types
+    let _: E = E::Struct;
+    //~^ ERROR expected value, found struct variant `E::Struct`
+    let _: E = E::Unit();
+    //~^ ERROR expected function, found enum variant `E::Unit`
+    let _: Z = m::n::Z;
+    //~^ ERROR cannot find type `Z` in this scope
+    //~| ERROR expected value, found enum `m::n::Z`
+    //~| ERROR enum `Z` is private
+    let _: Z = m::n::Z::Fn;
+    //~^ ERROR cannot find type `Z` in this scope
+    //~| ERROR enum `Z` is private
+    let _: Z = m::n::Z::Struct;
+    //~^ ERROR cannot find type `Z` in this scope
+    //~| ERROR expected value, found struct variant `m::n::Z::Struct`
+    //~| ERROR enum `Z` is private
+    let _: Z = m::n::Z::Unit {};
+    //~^ ERROR cannot find type `Z` in this scope
+    //~| ERROR enum `Z` is private
+}