Be more specific about constructor FnDefs in type mismatch

compiler/rustc_middle/src/ty/error.rs

@@ -2,10 +2,10 @@
 use crate::ty::diagnostics::suggest_constraining_type_param;
 use crate::ty::print::{with_forced_trimmed_paths, FmtPrinter, Printer};
 use crate::ty::{self, BoundRegionKind, Region, Ty, TyCtxt};
-use hir::def::DefKind;
 use rustc_errors::Applicability::{MachineApplicable, MaybeIncorrect};
 use rustc_errors::{pluralize, Diagnostic, MultiSpan};
 use rustc_hir as hir;
+use rustc_hir::def::{CtorOf, DefKind};
 use rustc_hir::def_id::DefId;
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{BytePos, Span};
@@ -319,7 +319,11 @@ pub fn sort_string(self, tcx: TyCtxt<'_>) -> Cow<'static, str> {
                     .into()
                 }
             }
-            ty::FnDef(..) => "fn item".into(),
+            ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
+                DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
+                DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
+                _ => "fn item".into(),
+            },
             ty::FnPtr(_) => "fn pointer".into(),
             ty::Dynamic(ref inner, ..) if let Some(principal) = inner.principal() => {
                 format!("trait object `dyn {}`", tcx.def_path_str(principal.def_id())).into()
@@ -366,7 +370,11 @@ pub fn prefix_string(self, tcx: TyCtxt<'_>) -> Cow<'static, str> {
                 _ => "reference",
             }
             .into(),
-            ty::FnDef(..) => "fn item".into(),
+            ty::FnDef(def_id, ..) => match tcx.def_kind(def_id) {
+                DefKind::Ctor(CtorOf::Struct, _) => "struct constructor".into(),
+                DefKind::Ctor(CtorOf::Variant, _) => "enum constructor".into(),
+                _ => "fn item".into(),
+            },
             ty::FnPtr(_) => "fn pointer".into(),
             ty::Dynamic(..) => "trait object".into(),
             ty::Closure(..) => "closure".into(),

tests/ui/issues/issue-35241.stderr

@@ -5,12 +5,12 @@ LL | struct Foo(u32);
    | ---------- fn(u32) -> Foo {Foo} defined here
 LL |
 LL | fn test() -> Foo { Foo }
-   |              ---   ^^^ expected struct `Foo`, found fn item
+   |              ---   ^^^ expected struct `Foo`, found struct constructor
    |              |
    |              expected `Foo` because of return type
    |
    = note:          expected struct `Foo`
-             found fn item `fn(u32) -> Foo {Foo}`
+           found struct constructor `fn(u32) -> Foo {Foo}`
 help: use parentheses to construct this tuple struct
    |
 LL | fn test() -> Foo { Foo(/* u32 */) }

tests/ui/resolve/privacy-enum-ctor.stderr

@@ -267,12 +267,12 @@ LL |             Fn(u8),
    |             -- fn(u8) -> Z {Z::Fn} defined here
 ...
 LL |         let _: Z = Z::Fn;
-   |                -   ^^^^^ expected enum `Z`, found fn item
+   |                -   ^^^^^ expected enum `Z`, found enum constructor
    |                |
    |                expected due to this
    |
    = note:          expected enum `Z`
-           found fn item `fn(u8) -> Z {Z::Fn}`
+           found enum constructor `fn(u8) -> Z {Z::Fn}`
 help: use parentheses to construct this tuple variant
    |
 LL |         let _: Z = Z::Fn(/* u8 */);
@@ -308,12 +308,12 @@ LL |         Fn(u8),
    |         -- fn(u8) -> E {E::Fn} defined here
 ...
 LL |     let _: E = m::E::Fn;
-   |            -   ^^^^^^^^ expected enum `E`, found fn item
+   |            -   ^^^^^^^^ expected enum `E`, found enum constructor
    |            |
    |            expected due to this
    |
    = note:          expected enum `E`
-           found fn item `fn(u8) -> E {E::Fn}`
+           found enum constructor `fn(u8) -> E {E::Fn}`
 help: use parentheses to construct this tuple variant
    |
 LL |     let _: E = m::E::Fn(/* u8 */);
@@ -349,12 +349,12 @@ LL |         Fn(u8),
    |         -- fn(u8) -> E {E::Fn} defined here
 ...
 LL |     let _: E = E::Fn;
-   |            -   ^^^^^ expected enum `E`, found fn item
+   |            -   ^^^^^ expected enum `E`, found enum constructor
    |            |
    |            expected due to this
    |
    = note:          expected enum `E`
-           found fn item `fn(u8) -> E {E::Fn}`
+           found enum constructor `fn(u8) -> E {E::Fn}`
 help: use parentheses to construct this tuple variant
    |
 LL |     let _: E = E::Fn(/* u8 */);

tests/ui/suggestions/fn-or-tuple-struct-without-args.stderr

@@ -23,12 +23,12 @@ LL | struct S(usize, usize);
    | -------- fn(usize, usize) -> S {S} defined here
 ...
 LL |     let _: S = S;
-   |            -   ^ expected struct `S`, found fn item
+   |            -   ^ expected struct `S`, found struct constructor
    |            |
    |            expected due to this
    |
    = note:          expected struct `S`
-             found fn item `fn(usize, usize) -> S {S}`
+           found struct constructor `fn(usize, usize) -> S {S}`
 help: use parentheses to construct this tuple struct
    |
 LL |     let _: S = S(/* usize */, /* usize */);
@@ -59,12 +59,12 @@ LL | struct V();
    | -------- fn() -> V {V} defined here
 ...
 LL |     let _: V = V;
-   |            -   ^ expected struct `V`, found fn item
+   |            -   ^ expected struct `V`, found struct constructor
    |            |
    |            expected due to this
    |
    = note:          expected struct `V`
-             found fn item `fn() -> V {V}`
+           found struct constructor `fn() -> V {V}`
 help: use parentheses to construct this tuple struct
    |
 LL |     let _: V = V();
@@ -113,12 +113,12 @@ LL |     A(usize),
    |     - fn(usize) -> E {E::A} defined here
 ...
 LL |     let _: E = E::A;
-   |            -   ^^^^ expected enum `E`, found fn item
+   |            -   ^^^^ expected enum `E`, found enum constructor
    |            |
    |            expected due to this
    |
    = note:          expected enum `E`
-           found fn item `fn(usize) -> E {E::A}`
+           found enum constructor `fn(usize) -> E {E::A}`
 help: use parentheses to construct this tuple variant
    |
 LL |     let _: E = E::A(/* usize */);

tests/ui/typeck/issue-87181/empty-tuple-method.rs

@@ -10,5 +10,5 @@ fn foo(&self) { }
 fn main() {
     let thing = Bar { bar: Foo };
     thing.bar.foo();
-    //~^ ERROR no method named `foo` found for fn item `fn() -> Foo {Foo}` in the current scope [E0599]
+    //~^ ERROR no method named `foo` found for struct constructor `fn() -> Foo {Foo}` in the current scope [E0599]
 }

tests/ui/typeck/issue-87181/empty-tuple-method.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `foo` found for fn item `fn() -> Foo {Foo}` in the current scope
+error[E0599]: no method named `foo` found for struct constructor `fn() -> Foo {Foo}` in the current scope
   --> $DIR/empty-tuple-method.rs:12:15
    |
 LL |     thing.bar.foo();

tests/ui/typeck/issue-87181/enum-variant.rs

@@ -12,5 +12,5 @@ fn foo(&self) { }
 fn main() {
     let thing = Bar { bar: Foo::Tup };
     thing.bar.foo();
-    //~^ ERROR no method named `foo` found for fn item `fn() -> Foo {Foo::Tup}` in the current scope [E0599]
+    //~^ ERROR no method named `foo` found for enum constructor `fn() -> Foo {Foo::Tup}` in the current scope [E0599]
 }

tests/ui/typeck/issue-87181/enum-variant.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `foo` found for fn item `fn() -> Foo {Foo::Tup}` in the current scope
+error[E0599]: no method named `foo` found for enum constructor `fn() -> Foo {Foo::Tup}` in the current scope
   --> $DIR/enum-variant.rs:14:15
    |
 LL |     thing.bar.foo();

tests/ui/typeck/issue-87181/tuple-method.rs

@@ -10,5 +10,5 @@ fn foo() { }
 fn main() {
     let thing = Bar { bar: Foo };
     thing.bar.foo();
-    //~^ ERROR no method named `foo` found for fn item `fn(u8, i32) -> Foo {Foo}` in the current scope [E0599]
+    //~^ ERROR no method named `foo` found for struct constructor `fn(u8, i32) -> Foo {Foo}` in the current scope [E0599]
 }

tests/ui/typeck/issue-87181/tuple-method.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `foo` found for fn item `fn(u8, i32) -> Foo {Foo}` in the current scope
+error[E0599]: no method named `foo` found for struct constructor `fn(u8, i32) -> Foo {Foo}` in the current scope
   --> $DIR/tuple-method.rs:12:15
    |
 LL |     thing.bar.foo();

tests/ui/typeck/issue-96738.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `nonexistent_method` found for fn item `fn(_) -> Option<_> {Option::<_>::Some}` in the current scope
+error[E0599]: no method named `nonexistent_method` found for enum constructor `fn(_) -> Option<_> {Option::<_>::Some}` in the current scope
   --> $DIR/issue-96738.rs:2:10
    |
 LL |     Some.nonexistent_method();