Rollup merge of #158392 - aerooneqq:delegation-defaults-in-generics-2, r=petrochenkov

jhpratt · web-flow · commit 35f0aa9b2663 · 2026-06-25T17:53:58.000-04:00
delegation: add tests for defaults and infers in generics This PR adds tests for interaction of default generic params and infers in delegation. Moreover, it groups delegation's pretty tests into a single folder and adds one test for generics. Comments in tests explain the behavior. Part of #118212. r? @petrochenkov
diff --git a/tests/pretty/delegation/auxiliary/to-reuse-functions.rs b/tests/pretty/delegation/auxiliary/to-reuse-functions.rs
diff --git a/tests/pretty/delegation/delegation.rs b/tests/pretty/delegation/delegation.rs
diff --git a/tests/pretty/delegation/generics.pp b/tests/pretty/delegation/generics.pp
@@ -0,0 +1,131 @@
+//@ pretty-compare-only
+//@ pretty-mode:hir
+//@ pp-exact:generics.pp
+
+#![allow(incomplete_features)]
+#![attr = Feature([fn_delegation#0])]
+extern crate std;
+#[attr = PreludeImport]
+use ::std::prelude::rust_2015::*;
+
+mod free_to_trait {
+    trait Trait<'a, XX, Y, T = (), const N: usize = 2> {
+        fn method<A, B>(&self, t: (T, A, B), slice: &'_ [usize; N]) { }
+        fn r#static<A, B>(t: (T, A, B), slice: &'_ [usize; N]) { }
+    }
+
+    struct X;
+    impl <XX, Y, T, const N: usize> Trait<'_, XX, Y, T, N> for X { }
+
+    // When infer is specified for default parameter the generic param is generated.
+    #[attr = Inline(Hint)]
+    fn foo<'a, Self, XX, Y, T, const N: _, A, B>(self: _, arg1: _, arg2: _)
+        -> _ where
+        'a:'a {
+        <Self as Trait::<'a, XX, Y, T, N>>::method::<A, B>(self, arg1, arg2)
+    }
+    #[attr = Inline(Hint)]
+    fn static_foo<'a, Self, XX, Y, T, const N: _, A, B>(arg0: _, arg1: _) -> _
+        where
+        'a:'a {
+        <Self as Trait::<'a, XX, Y, T, N>>::r#static::<A, B>(arg0, arg1)
+    }
+
+    // When default params are omitted they are not generated but used in signature inheritance.
+    #[attr = Inline(Hint)]
+    fn bar<'a, Self, XX, Y, A, B>(self: _, arg1: _, arg2: _) -> _ where
+        'a:'a {
+        <Self as Trait::<'a, XX, Y>>::method::<A, B>(self, arg1, arg2)
+    }
+    #[attr = Inline(Hint)]
+    fn static_bar<'a, Self, XX, Y, A, B>(arg0: _, arg1: _) -> _ where
+        'a:'a { <Self as Trait::<'a, XX, Y>>::r#static::<A, B>(arg0, arg1) }
+
+    // Check with user specified args in child:
+    // When infer is specified for default parameter the generic param is generated.
+    #[attr = Inline(Hint)]
+    fn foo1<'a, Self, XX, Y, T, const N: _, B>(self: _, arg1: _, arg2: _) -> _
+        where
+        'a:'a {
+        <Self as Trait::<'a, XX, Y, T, N>>::method::<(), B>(self, arg1, arg2)
+    }
+    #[attr = Inline(Hint)]
+    fn static_foo1<'a, Self, XX, Y, T, const N: _, B>(arg0: _, arg1: _) -> _
+        where
+        'a:'a {
+        <Self as Trait::<'a, XX, Y, T, N>>::r#static::<(), B>(arg0, arg1)
+    }
+
+    // When default params are omitted they are not generated but used in signature inheritance.
+    #[attr = Inline(Hint)]
+    fn bar1<'a, Self, XX, Y, A>(self: _, arg1: _, arg2: _) -> _ where
+        'a:'a {
+        <Self as Trait::<'a, XX, Y>>::method::<A, ()>(self, arg1, arg2)
+    }
+    #[attr = Inline(Hint)]
+    fn static_bar1<'a, Self, XX, Y, A>(arg0: _, arg1: _) -> _ where
+        'a:'a { <Self as Trait::<'a, XX, Y>>::r#static::<A, ()>(arg0, arg1) }
+
+    // Check with explicit self type.
+    #[attr = Inline(Hint)]
+    fn foo2<'a, XX, Y, T, const N: _, A, B>(self: _, arg1: _, arg2: _) -> _
+        where
+        'a:'a {
+        <X as Trait::<'a, XX, Y, T, N>>::method::<A, B>(self, arg1, arg2)
+    }
+    #[attr = Inline(Hint)]
+    fn static_foo2<'a, XX, Y, T, const N: _, A, B>(arg0: _, arg1: _) -> _
+        where
+        'a:'a {
+        <X as Trait::<'a, XX, Y, T, N>>::r#static::<A, B>(arg0, arg1)
+    }
+
+    #[attr = Inline(Hint)]
+    fn bar2<'a, XX, Y, A, B>(self: _, arg1: _, arg2: _) -> _ where
+        'a:'a { <X as Trait::<'a, XX, Y>>::method::<A, B>(self, arg1, arg2) }
+    #[attr = Inline(Hint)]
+    fn static_bar2<'a, XX, Y, A, B>(arg0: _, arg1: _) -> _ where
+        'a:'a { <X as Trait::<'a, XX, Y>>::r#static::<A, B>(arg0, arg1) }
+
+    #[attr = Inline(Hint)]
+    fn foo3<'a, XX, Y, T, const N: _, B>(self: _, arg1: _, arg2: _) -> _ where
+        'a:'a {
+        <X as Trait::<'a, XX, Y, T, N>>::method::<(), B>(self, arg1, arg2)
+    }
+    #[attr = Inline(Hint)]
+    fn static_foo3<'a, XX, Y, T, const N: _, B>(arg0: _, arg1: _) -> _ where
+        'a:'a {
+        <X as Trait::<'a, XX, Y, T, N>>::r#static::<(), B>(arg0, arg1)
+    }
+
+    #[attr = Inline(Hint)]
+    fn bar3<'a, XX, Y, A>(self: _, arg1: _, arg2: _) -> _ where
+        'a:'a { <X as Trait::<'a, XX, Y>>::method::<A, ()>(self, arg1, arg2) }
+    #[attr = Inline(Hint)]
+    fn static_bar3<'a, XX, Y, A>(arg0: _, arg1: _) -> _ where
+        'a:'a { <X as Trait::<'a, XX, Y>>::r#static::<A, ()>(arg0, arg1) }
+}
+
+mod trait_impl_to_trait {
+    trait Trait<'a, X, Y, T = (), const N: usize = 2> {
+        fn foo(&self, t: (T, T, T), slice: &'_ [usize; N]) { }
+        fn bar(&self, t: (T, T, T), slice: &'_ [usize; N]) { }
+    }
+
+    struct S;
+    impl <X, Y> Trait<'_, X, Y> for S { }
+
+    struct W(S);
+    impl <X, Y> Trait<'_, X, Y> for W {
+        // Generics of both methods match generics of their signature
+        // functions in `Trait` declaration, no matter specified infers.
+        #[attr = Inline(Hint)]
+        fn foo(self: _, arg1: _, arg2: _)
+            -> _ { Trait::<'static, X, Y>::foo(self.0, arg1, arg2) }
+        #[attr = Inline(Hint)]
+        fn bar(self: _, arg1: _, arg2: _)
+            -> _ { Trait::<'static, X, Y, _, _>::foo(self.0, arg1, arg2) }
+    }
+}
+
+fn main() { }
diff --git a/tests/pretty/delegation/generics.rs b/tests/pretty/delegation/generics.rs
@@ -0,0 +1,66 @@
+//@ pretty-compare-only
+//@ pretty-mode:hir
+//@ pp-exact:generics.pp
+
+#![allow(incomplete_features)]
+#![feature(fn_delegation)]
+
+mod free_to_trait {
+    trait Trait<'a, XX, Y, T = (), const N: usize = 2> {
+        fn method<A, B>(&self, t: (T, A, B), slice: &[usize; N]) {}
+        fn r#static<A, B>(t: (T, A, B), slice: &[usize; N]) {}
+    }
+
+    struct X;
+    impl<XX, Y, T, const N: usize> Trait<'_, XX, Y, T, N> for X {}
+
+    // When infer is specified for default parameter the generic param is generated.
+    reuse Trait::<'_, _, _, _, _>::method as foo;
+    reuse Trait::<'_, _, _, _, _>::r#static as static_foo;
+
+    // When default params are omitted they are not generated but used in signature inheritance.
+    reuse Trait::<'_, _, _>::method as bar;
+    reuse Trait::<'_, _, _>::r#static as static_bar;
+
+    // Check with user specified args in child:
+    // When infer is specified for default parameter the generic param is generated.
+    reuse Trait::<'_, _, _, _, _>::method::<(), _> as foo1;
+    reuse Trait::<'_, _, _, _, _>::r#static::<(), _> as static_foo1;
+
+    // When default params are omitted they are not generated but used in signature inheritance.
+    reuse Trait::<'_, _, _>::method::<_, ()> as bar1;
+    reuse Trait::<'_, _, _>::r#static::<_, ()> as static_bar1;
+
+    // Check with explicit self type.
+    reuse <X as Trait::<'_, _, _, _, _>>::method as foo2;
+    reuse <X as Trait::<'_, _, _, _, _>>::r#static as static_foo2;
+
+    reuse <X as Trait::<'_, _, _>>::method as bar2;
+    reuse <X as Trait::<'_, _, _>>::r#static as static_bar2;
+
+    reuse <X as Trait::<'_, _, _, _, _>>::method::<(), _> as foo3;
+    reuse <X as Trait::<'_, _, _, _, _>>::r#static::<(), _> as static_foo3;
+
+    reuse <X as Trait::<'_, _, _>>::method::<_, ()> as bar3;
+    reuse <X as Trait::<'_, _, _>>::r#static::<_, ()> as static_bar3;
+}
+
+mod trait_impl_to_trait {
+    trait Trait<'a, X, Y, T = (), const N: usize = 2> {
+        fn foo(&self, t: (T, T, T), slice: &[usize; N]) {}
+        fn bar(&self, t: (T, T, T), slice: &[usize; N]) {}
+    }
+
+    struct S;
+    impl<X, Y> Trait<'_, X, Y> for S {}
+
+    struct W(S);
+    impl<X, Y> Trait<'_, X, Y> for W {
+        // Generics of both methods match generics of their signature
+        // functions in `Trait` declaration, no matter specified infers.
+        reuse Trait::<'static, X, Y>::foo { self.0 }
+        reuse Trait::<'static, X, Y, _, _>::foo as bar { self.0 }
+    }
+}
+
+fn main() {}
diff --git a/tests/pretty/delegation/impl-reuse.pp b/tests/pretty/delegation/impl-reuse.pp
@@ -2,7 +2,7 @@
 #![no_std]
 //@ pretty-compare-only
 //@ pretty-mode:expanded
-//@ pp-exact:delegation-impl-reuse.pp
+//@ pp-exact:impl-reuse.pp
 
 #![allow(incomplete_features)]
 #![feature(fn_delegation)]
diff --git a/tests/pretty/delegation/impl-reuse.rs b/tests/pretty/delegation/impl-reuse.rs
@@ -1,6 +1,6 @@
 //@ pretty-compare-only
 //@ pretty-mode:expanded
-//@ pp-exact:delegation-impl-reuse.pp
+//@ pp-exact:impl-reuse.pp
 
 #![allow(incomplete_features)]
 #![feature(fn_delegation)]
diff --git a/tests/pretty/delegation/inherit-attributes.pp b/tests/pretty/delegation/inherit-attributes.pp
@@ -2,7 +2,7 @@
 //@ aux-crate:to_reuse_functions=to-reuse-functions.rs
 //@ pretty-mode:hir
 //@ pretty-compare-only
-//@ pp-exact:delegation-inherit-attributes.pp
+//@ pp-exact:inherit-attributes.pp
 
 #![allow(incomplete_features)]
 #![attr = Feature([fn_delegation#0])]
diff --git a/tests/pretty/delegation/inherit-attributes.rs b/tests/pretty/delegation/inherit-attributes.rs
@@ -2,7 +2,7 @@
 //@ aux-crate:to_reuse_functions=to-reuse-functions.rs
 //@ pretty-mode:hir
 //@ pretty-compare-only
-//@ pp-exact:delegation-inherit-attributes.pp
+//@ pp-exact:inherit-attributes.pp
 
 #![allow(incomplete_features)]
 #![feature(fn_delegation)]
diff --git a/tests/pretty/delegation/inline-attribute.pp b/tests/pretty/delegation/inline-attribute.pp
@@ -1,6 +1,6 @@
 //@ pretty-compare-only
 //@ pretty-mode:hir
-//@ pp-exact:delegation-inline-attribute.pp
+//@ pp-exact:inline-attribute.pp
 
 #![allow(incomplete_features)]
 #![attr = Feature([fn_delegation#0])]
diff --git a/tests/pretty/delegation/inline-attribute.rs b/tests/pretty/delegation/inline-attribute.rs
@@ -1,6 +1,6 @@
 //@ pretty-compare-only
 //@ pretty-mode:hir
-//@ pp-exact:delegation-inline-attribute.pp
+//@ pp-exact:inline-attribute.pp
 
 #![allow(incomplete_features)]
 #![feature(fn_delegation)]
diff --git a/tests/pretty/delegation/self-rename.pp b/tests/pretty/delegation/self-rename.pp
@@ -4,7 +4,7 @@
 use ::std::prelude::rust_2015::*;
 //@ pretty-compare-only
 //@ pretty-mode:hir
-//@ pp-exact:delegation-self-rename.pp
+//@ pp-exact:self-rename.pp
 
 
 trait Trait<'a, A, const B: bool> {
diff --git a/tests/pretty/delegation/self-rename.rs b/tests/pretty/delegation/self-rename.rs
@@ -1,6 +1,6 @@
 //@ pretty-compare-only
 //@ pretty-mode:hir
-//@ pp-exact:delegation-self-rename.pp
+//@ pp-exact:self-rename.pp
 
 #![feature(fn_delegation)]
 
diff --git a/tests/ui/delegation/generics/infer-defaults.rs b/tests/ui/delegation/generics/infer-defaults.rs
@@ -0,0 +1,124 @@
+#![feature(fn_delegation)]
+
+mod free_to_trait {
+    trait Trait<'a, XX, Y, T = (), const N: usize = 2> {
+        fn foo<A, B>(&self, t: (T, A, B), slice: &[usize; N]) {}
+    }
+
+    struct X;
+    impl<XX, Y, T, const N: usize> Trait<'_, XX, Y, T, N> for X {}
+
+    // When infer is specified for default parameter the generic param is generated.
+    reuse Trait::<'_, _, _, _, _>::foo as foo;
+    // When default params are omitted they are not generated but used in signature inheritance.
+    reuse Trait::<'_, _, _>::foo as bar;
+
+    // Check with user specified args in child:
+    // When infer is specified for default parameter the generic param is generated.
+    reuse Trait::<'_, _, _, _, _>::foo::<(), _> as foo1;
+    // When default params are omitted they are not generated but used in signature inheritance.
+    reuse Trait::<'_, _, _>::foo::<_, ()> as bar1;
+
+    // Check with explicit self type.
+    reuse <X as Trait::<'_, _, _, _, _>>::foo as foo2;
+    reuse <X as Trait::<'_, _, _>>::foo as bar2;
+
+    reuse <X as Trait::<'_, _, _, _, _>>::foo::<(), _> as foo3;
+    reuse <X as Trait::<'_, _, _>>::foo::<_, ()> as bar3;
+
+    fn check() {
+        foo::<'static, X, (), (), (), 1, (), ()>(&X, ((), (), ()), &[1]);
+        bar::<'static, X, (), (), (), ()>(&X, ((), (), ()), &[1, 2]);
+
+        foo1::<'static, X, (), (), (), 2, ()>(&X, ((), (), ()), &[1, 2]);
+        bar1::<'static, X, (), (), ()>(&X, ((), (), ()), &[1, 2]);
+
+        foo2::<'static, (), (), (), 3, (), ()>(&X, ((), (), ()), &[1, 2, 3]);
+        bar2::<'static, (), (), (), ()>(&X, ((), (), ()), &[1, 2]);
+
+        foo3::<'static, (), (), (), 4, ()>(&X, ((), (), ()), &[1, 2, 3, 4]);
+        bar3::<'static, (), (), ()>(&X, ((), (), ()), &[1, 2]);
+    }
+}
+
+mod trait_to_trait {
+    trait Trait<'a, X, Y, T = (), const N: usize = 2> {
+        fn foo(&self, t: (T, T, T), slice: &[usize; N]) {}
+        fn bar(&self, t: (T, T, T), slice: &[usize; N]) {}
+    }
+
+    trait Trait2<'a, X, Y>: Trait<'a, X, Y> {
+        // Default params are generated as usual generics as infers are specified.
+        reuse Trait::<'a, X, Y, _, _>::foo;
+        //~^ ERROR: the trait bound `Self: trait_to_trait::Trait<'a, X, Y, T, N>` is not satisfied
+
+        // Default params are not generated, as they are not specified.
+        reuse Trait::<'a, X, Y>::foo as bar;
+    }
+
+    impl Trait<'static, (), ()> for () {}
+    impl Trait2<'static, (), ()> for () {}
+
+    fn check() {
+        Trait2::<'static, (), ()>::foo::<(), 1>(&(), ((), (), ()), &[1]);
+        Trait2::<'static, (), ()>::bar(&(), ((), (), ()), &[1, 2]);
+    }
+}
+
+mod trait_impl_to_trait {
+    trait Trait<'a, X, Y, T = (), const N: usize = 2> {
+        fn foo(&self, t: (T, T, T), slice: &[usize; N]) {}
+        fn bar(&self, t: (T, T, T), slice: &[usize; N]) {}
+    }
+
+    struct S;
+    impl<X, Y> Trait<'_, X, Y> for S {}
+
+    struct W(S);
+    impl<X, Y> Trait<'_, X, Y> for W {
+        // Generics of both methods match generics of their signature
+        // functions in `Trait` declaration, no matter specified infers.
+        reuse Trait::<'static, X, Y>::foo { self.0 }
+        reuse Trait::<'static, X, Y, _, _>::foo as bar { self.0 }
+    }
+
+    fn check() {
+        W(S).foo(((), (), ()), &[1, 2]);
+        W(S).foo::<1, 2, 3>(((), (), ()), &[1, 2]);
+        //~^ ERROR: method takes 0 generic arguments but 3 generic arguments were supplied
+
+        W(S).bar(((), (), ()), &[1]);
+        //~^ ERROR: mismatched types
+        W(S).bar::<((), ()), 0>(((), (), ()), &[1, 2]);
+        //~^ ERROR: method takes 0 generic arguments but 2 generic arguments were supplied
+
+        W(S).bar(((), (), ()), &[1, 2]);
+    }
+}
+
+mod inherent_impl_to_trait {
+    trait Trait<'a, X, Y, T = (), const N: usize = 2> {
+        fn foo(&self, t: (T, T, T), slice: &[usize; N]) {}
+    }
+
+    struct S<T>(T);
+
+    impl<T: Trait<'static, (), ()>> S<T> {
+        // Default params are not generated, as they are not specified.
+        reuse Trait::<'static, (), ()>::foo { self.0 }
+
+        // Default params are generated as usual generics as infers are specified.
+        reuse Trait::<'static, (), (), _, _>::foo as bar { self.0 }
+        //~^ ERROR: the trait bound `T: inherent_impl_to_trait::Trait<'static, (), (), T, N>` is not satisfied
+    }
+
+    impl Trait<'static, (), ()> for () {}
+
+    fn check() {
+        S(()).foo(((), (), ()), &[1, 2]);
+        S(()).bar(((), (), ()), &[1, 2]);
+        S(()).bar::<usize, 4>((1, 2, 3), &[1, 2, 3, 4]);
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/delegation/generics/infer-defaults.stderr b/tests/ui/delegation/generics/infer-defaults.stderr
