Add tests and snapshot of current result

Author: mu001999

tests/ui/lint/dead-code/unused-assoc-ty.rs

@@ -0,0 +1,73 @@
+//@ check-pass
+
+#![deny(dead_code)]
+
+trait Tr {
+    type A;
+    type B;
+    type C: Default;
+    type D;
+    type E;
+    type F;
+    type G;
+    type H;
+}
+
+impl Tr for i32 {
+    type A = Self;
+    type B = Self;
+    type C = Self;
+    type D = Self;
+    type E = Self;
+    type F = Self;
+    type G = Self;
+    type H = Self;
+}
+
+trait Tr2 {
+    type A;
+}
+
+impl Tr2 for i32 {
+    type A = Self;
+}
+
+struct Foo<T: Tr2> {
+    _x: T::A,
+}
+
+struct Bar<T> {
+    _x: T
+}
+
+impl<T> Bar<T>
+where
+    T: Tr2<A = i32>
+{}
+
+type Baz<T> = <T as Tr>::G;
+
+struct FooBaz<T: Tr> {
+    _x: Baz<T>,
+}
+
+fn foo<T: Tr>(t: impl Tr<A = T>) -> impl Tr
+where
+    T::B: Copy
+{
+    let _a: T::C = Default::default();
+    baz::<T::F>();
+    t
+}
+fn bar<T: ?Sized>() {}
+fn baz<T>() {}
+
+fn main() {
+    foo::<i32>(42);
+    bar::<dyn Tr2<A = i32>>();
+    let _d: <i32 as Tr>::D = Default::default();
+    baz::<<i32 as Tr>::E>();
+    baz::<Foo<i32>>();
+    baz::<Bar<i32>>();
+    baz::<FooBaz<i32>>();
+}

tests/ui/lint/dead-code/used-assoc-ty-in-struct.rs

@@ -0,0 +1,16 @@
+//@ check-pass
+
+#![deny(dead_code)]
+
+trait Trait { type Ty; }
+
+impl Trait for () { type Ty = (); }
+
+pub struct Wrap(Inner<()>);
+struct Inner<T: Trait>(T::Ty); // <- use of QPath::TypeRelative `Ty` in a non-body only
+
+impl Wrap {
+    pub fn live(self) { _ = self.0; }
+}
+
+fn main() {}

tests/ui/lint/dead-code/used-assoc-ty-on-const.rs

@@ -0,0 +1,19 @@
+//@ check-pass
+
+#![deny(dead_code)]
+
+pub struct A;
+
+trait B {
+    type Assoc;
+}
+
+impl B for A {
+    type Assoc = A;
+}
+
+const X: <A as B>::Assoc = A;
+
+fn main() {
+    let _x: A = X;
+}

tests/ui/lint/dead-code/used-assoc-ty-on-impl.rs

@@ -0,0 +1,23 @@
+//@ check-pass
+
+#![deny(dead_code)]
+
+pub struct A;
+
+trait B {
+    type Assoc;
+}
+
+impl B for A {
+    type Assoc = A;
+}
+
+trait C {}
+
+impl C for <A as B>::Assoc {}
+
+fn foo<T: C>() {}
+
+fn main() {
+    foo::<A>();
+}

tests/ui/lint/dead-code/used-inherent-assoc-ty.rs

@@ -0,0 +1,12 @@
+//@ check-pass
+
+#![feature(inherent_associated_types)]
+#![allow(incomplete_features)]
+#[deny(dead_code)]
+
+fn main() {
+    let _: Struct::Item = ();
+}
+
+struct Struct;
+impl Struct { type Item = (); }

tests/ui/lint/dead-code/used-let-decl-in-body.rs

@@ -0,0 +1,21 @@
+//@ check-pass
+
+#![deny(dead_code)]
+
+trait Tr {
+    type X;
+}
+
+struct T;
+
+impl Tr for T {
+    type X = Self;
+}
+
+fn foo<T: Tr>() where {
+    let _: T::X;
+}
+
+fn main() {
+    foo::<T>();
+}