1 files changed, 1598 insertions, 0 deletions

diff --git a/crates/ra_hir_ty/src/tests/traits.rs b/crates/ra_hir_ty/src/tests/traits.rs
new file mode 100644
index 000000000..ae316922b
--- /dev/null
+++ b/crates/ra_hir_ty/src/tests/traits.rs
@@ -0,0 +1,1598 @@
+use insta::assert_snapshot;
+
+use ra_db::fixture::WithFixture;
+use test_utils::covers;
+
+use super::{infer, infer_with_mismatches, type_at, type_at_pos};
+use crate::test_db::TestDB;
+
+#[test]
+fn infer_await() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+
+struct IntFuture;
+
+impl Future for IntFuture {
+    type Output = u64;
+}
+
+fn test() {
+    let r = IntFuture;
+    let v = r.await;
+    v<|>;
+}
+
+//- /std.rs crate:std
+#[prelude_import] use future::*;
+mod future {
+    trait Future {
+        type Output;
+    }
+}
+
+"#,
+    );
+    assert_eq!("u64", type_at_pos(&db, pos));
+}
+
+#[test]
+fn infer_try() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+
+fn test() {
+    let r: Result<i32, u64> = Result::Ok(1);
+    let v = r?;
+    v<|>;
+}
+
+//- /std.rs crate:std
+
+#[prelude_import] use ops::*;
+mod ops {
+    trait Try {
+        type Ok;
+        type Error;
+    }
+}
+
+#[prelude_import] use result::*;
+mod result {
+    enum Result<O, E> {
+        Ok(O),
+        Err(E)
+    }
+
+    impl<O, E> crate::ops::Try for Result<O, E> {
+        type Ok = O;
+        type Error = E;
+    }
+}
+
+"#,
+    );
+    assert_eq!("i32", type_at_pos(&db, pos));
+}
+
+#[test]
+fn infer_for_loop() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+
+use std::collections::Vec;
+
+fn test() {
+    let v = Vec::new();
+    v.push("foo");
+    for x in v {
+        x<|>;
+    }
+}
+
+//- /std.rs crate:std
+
+#[prelude_import] use iter::*;
+mod iter {
+    trait IntoIterator {
+        type Item;
+    }
+}
+
+mod collections {
+    struct Vec<T> {}
+    impl<T> Vec<T> {
+        fn new() -> Self { Vec {} }
+        fn push(&mut self, t: T) { }
+    }
+
+    impl<T> crate::iter::IntoIterator for Vec<T> {
+        type Item=T;
+    }
+}
+"#,
+    );
+    assert_eq!("&str", type_at_pos(&db, pos));
+}
+
+#[test]
+fn infer_ops_neg() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+
+struct Bar;
+struct Foo;
+
+impl std::ops::Neg for Bar {
+    type Output = Foo;
+}
+
+fn test() {
+    let a = Bar;
+    let b = -a;
+    b<|>;
+}
+
+//- /std.rs crate:std
+
+#[prelude_import] use ops::*;
+mod ops {
+    pub trait Neg {
+        type Output;
+    }
+}
+"#,
+    );
+    assert_eq!("Foo", type_at_pos(&db, pos));
+}
+
+#[test]
+fn infer_ops_not() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+
+struct Bar;
+struct Foo;
+
+impl std::ops::Not for Bar {
+    type Output = Foo;
+}
+
+fn test() {
+    let a = Bar;
+    let b = !a;
+    b<|>;
+}
+
+//- /std.rs crate:std
+
+#[prelude_import] use ops::*;
+mod ops {
+    pub trait Not {
+        type Output;
+    }
+}
+"#,
+    );
+    assert_eq!("Foo", type_at_pos(&db, pos));
+}
+
+#[test]
+fn infer_from_bound_1() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait<T> {}
+struct S<T>(T);
+impl<U> Trait<U> for S<U> {}
+fn foo<T: Trait<u32>>(t: T) {}
+fn test() {
+    let s = S(unknown);
+    foo(s);
+}
+"#),
+        @r###"
+    [86; 87) 't': T
+    [92; 94) '{}': ()
+    [105; 144) '{     ...(s); }': ()
+    [115; 116) 's': S<u32>
+    [119; 120) 'S': S<u32>(T) -> S<T>
+    [119; 129) 'S(unknown)': S<u32>
+    [121; 128) 'unknown': u32
+    [135; 138) 'foo': fn foo<S<u32>>(T) -> ()
+    [135; 141) 'foo(s)': ()
+    [139; 140) 's': S<u32>
+    "###
+    );
+}
+
+#[test]
+fn infer_from_bound_2() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait<T> {}
+struct S<T>(T);
+impl<U> Trait<U> for S<U> {}
+fn foo<U, T: Trait<U>>(t: T) -> U {}
+fn test() {
+    let s = S(unknown);
+    let x: u32 = foo(s);
+}
+"#),
+        @r###"
+    [87; 88) 't': T
+    [98; 100) '{}': ()
+    [111; 163) '{     ...(s); }': ()
+    [121; 122) 's': S<u32>
+    [125; 126) 'S': S<u32>(T) -> S<T>
+    [125; 135) 'S(unknown)': S<u32>
+    [127; 134) 'unknown': u32
+    [145; 146) 'x': u32
+    [154; 157) 'foo': fn foo<u32, S<u32>>(T) -> U
+    [154; 160) 'foo(s)': u32
+    [158; 159) 's': S<u32>
+    "###
+    );
+}
+
+#[test]
+fn infer_project_associated_type() {
+    // y, z, a don't yet work because of https://github.com/rust-lang/chalk/issues/234
+    assert_snapshot!(
+        infer(r#"
+trait Iterable {
+   type Item;
+}
+struct S;
+impl Iterable for S { type Item = u32; }
+fn test<T: Iterable>() {
+    let x: <S as Iterable>::Item = 1;
+    let y: <T as Iterable>::Item = no_matter;
+    let z: T::Item = no_matter;
+    let a: <T>::Item = no_matter;
+}
+"#),
+        @r###"
+    [108; 261) '{     ...ter; }': ()
+    [118; 119) 'x': u32
+    [145; 146) '1': u32
+    [156; 157) 'y': {unknown}
+    [183; 192) 'no_matter': {unknown}
+    [202; 203) 'z': {unknown}
+    [215; 224) 'no_matter': {unknown}
+    [234; 235) 'a': {unknown}
+    [249; 258) 'no_matter': {unknown}
+    "###
+    );
+}
+
+#[test]
+fn infer_return_associated_type() {
+    assert_snapshot!(
+        infer(r#"
+trait Iterable {
+   type Item;
+}
+struct S;
+impl Iterable for S { type Item = u32; }
+fn foo1<T: Iterable>(t: T) -> T::Item {}
+fn foo2<T: Iterable>(t: T) -> <T as Iterable>::Item {}
+fn foo3<T: Iterable>(t: T) -> <T>::Item {}
+fn test() {
+    let x = foo1(S);
+    let y = foo2(S);
+    let z = foo3(S);
+}
+"#),
+        @r###"
+    [106; 107) 't': T
+    [123; 125) '{}': ()
+    [147; 148) 't': T
+    [178; 180) '{}': ()
+    [202; 203) 't': T
+    [221; 223) '{}': ()
+    [234; 300) '{     ...(S); }': ()
+    [244; 245) 'x': u32
+    [248; 252) 'foo1': fn foo1<S>(T) -> <T as Iterable>::Item
+    [248; 255) 'foo1(S)': u32
+    [253; 254) 'S': S
+    [265; 266) 'y': u32
+    [269; 273) 'foo2': fn foo2<S>(T) -> <T as Iterable>::Item
+    [269; 276) 'foo2(S)': u32
+    [274; 275) 'S': S
+    [286; 287) 'z': u32
+    [290; 294) 'foo3': fn foo3<S>(T) -> <T as Iterable>::Item
+    [290; 297) 'foo3(S)': u32
+    [295; 296) 'S': S
+    "###
+    );
+}
+
+#[test]
+fn infer_associated_type_bound() {
+    assert_snapshot!(
+        infer(r#"
+trait Iterable {
+   type Item;
+}
+fn test<T: Iterable<Item=u32>>() {
+    let y: T::Item = unknown;
+}
+"#),
+        @r###"
+    [67; 100) '{     ...own; }': ()
+    [77; 78) 'y': {unknown}
+    [90; 97) 'unknown': {unknown}
+    "###
+    );
+}
+
+#[test]
+fn infer_const_body() {
+    assert_snapshot!(
+        infer(r#"
+const A: u32 = 1 + 1;
+static B: u64 = { let x = 1; x };
+"#),
+        @r###"
+    [16; 17) '1': u32
+    [16; 21) '1 + 1': u32
+    [20; 21) '1': u32
+    [39; 55) '{ let ...1; x }': u64
+    [45; 46) 'x': u64
+    [49; 50) '1': u64
+    [52; 53) 'x': u64
+    "###
+    );
+}
+
+#[test]
+fn tuple_struct_fields() {
+    assert_snapshot!(
+        infer(r#"
+struct S(i32, u64);
+fn test() -> u64 {
+    let a = S(4, 6);
+    let b = a.0;
+    a.1
+}
+"#),
+        @r###"
+    [38; 87) '{     ... a.1 }': u64
+    [48; 49) 'a': S
+    [52; 53) 'S': S(i32, u64) -> S
+    [52; 59) 'S(4, 6)': S
+    [54; 55) '4': i32
+    [57; 58) '6': u64
+    [69; 70) 'b': i32
+    [73; 74) 'a': S
+    [73; 76) 'a.0': i32
+    [82; 83) 'a': S
+    [82; 85) 'a.1': u64
+    "###
+    );
+}
+
+#[test]
+fn tuple_struct_with_fn() {
+    assert_snapshot!(
+        infer(r#"
+struct S(fn(u32) -> u64);
+fn test() -> u64 {
+    let a = S(|i| 2*i);
+    let b = a.0(4);
+    a.0(2)
+}
+"#),
+        @r###"
+    [44; 102) '{     ...0(2) }': u64
+    [54; 55) 'a': S
+    [58; 59) 'S': S(fn(u32) -> u64) -> S
+    [58; 68) 'S(|i| 2*i)': S
+    [60; 67) '|i| 2*i': |u32| -> u64
+    [61; 62) 'i': u32
+    [64; 65) '2': u32
+    [64; 67) '2*i': u32
+    [66; 67) 'i': u32
+    [78; 79) 'b': u64
+    [82; 83) 'a': S
+    [82; 85) 'a.0': fn(u32) -> u64
+    [82; 88) 'a.0(4)': u64
+    [86; 87) '4': u32
+    [94; 95) 'a': S
+    [94; 97) 'a.0': fn(u32) -> u64
+    [94; 100) 'a.0(2)': u64
+    [98; 99) '2': u32
+    "###
+    );
+}
+
+#[test]
+fn indexing_arrays() {
+    assert_snapshot!(
+        infer("fn main() { &mut [9][2]; }"),
+        @r###"
+    [10; 26) '{ &mut...[2]; }': ()
+    [12; 23) '&mut [9][2]': &mut {unknown}
+    [17; 20) '[9]': [i32;_]
+    [17; 23) '[9][2]': {unknown}
+    [18; 19) '9': i32
+    [21; 22) '2': i32
+    "###
+    )
+}
+
+#[test]
+fn infer_ops_index() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+
+struct Bar;
+struct Foo;
+
+impl std::ops::Index<u32> for Bar {
+    type Output = Foo;
+}
+
+fn test() {
+    let a = Bar;
+    let b = a[1];
+    b<|>;
+}
+
+//- /std.rs crate:std
+
+#[prelude_import] use ops::*;
+mod ops {
+    pub trait Index<Idx> {
+        type Output;
+    }
+}
+"#,
+    );
+    assert_eq!("Foo", type_at_pos(&db, pos));
+}
+
+#[test]
+fn deref_trait() {
+    let t = type_at(
+        r#"
+//- /main.rs
+#[lang = "deref"]
+trait Deref {
+    type Target;
+    fn deref(&self) -> &Self::Target;
+}
+
+struct Arc<T>;
+impl<T> Deref for Arc<T> {
+    type Target = T;
+}
+
+struct S;
+impl S {
+    fn foo(&self) -> u128 {}
+}
+
+fn test(s: Arc<S>) {
+    (*s, s.foo())<|>;
+}
+"#,
+    );
+    assert_eq!(t, "(S, u128)");
+}
+
+#[test]
+fn deref_trait_with_inference_var() {
+    let t = type_at(
+        r#"
+//- /main.rs
+#[lang = "deref"]
+trait Deref {
+    type Target;
+    fn deref(&self) -> &Self::Target;
+}
+
+struct Arc<T>;
+fn new_arc<T>() -> Arc<T> {}
+impl<T> Deref for Arc<T> {
+    type Target = T;
+}
+
+struct S;
+fn foo(a: Arc<S>) {}
+
+fn test() {
+    let a = new_arc();
+    let b = (*a)<|>;
+    foo(a);
+}
+"#,
+    );
+    assert_eq!(t, "S");
+}
+
+#[test]
+fn deref_trait_infinite_recursion() {
+    let t = type_at(
+        r#"
+//- /main.rs
+#[lang = "deref"]
+trait Deref {
+    type Target;
+    fn deref(&self) -> &Self::Target;
+}
+
+struct S;
+
+impl Deref for S {
+    type Target = S;
+}
+
+fn test(s: S) {
+    s.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn deref_trait_with_question_mark_size() {
+    let t = type_at(
+        r#"
+//- /main.rs
+#[lang = "deref"]
+trait Deref {
+    type Target;
+    fn deref(&self) -> &Self::Target;
+}
+
+struct Arc<T>;
+impl<T> Deref for Arc<T> {
+    type Target = T;
+}
+
+struct S;
+impl S {
+    fn foo(&self) -> u128 {}
+}
+
+fn test(s: Arc<S>) {
+    (*s, s.foo())<|>;
+}
+"#,
+    );
+    assert_eq!(t, "(S, u128)");
+}
+
+#[test]
+fn obligation_from_function_clause() {
+    let t = type_at(
+        r#"
+//- /main.rs
+struct S;
+
+trait Trait<T> {}
+impl Trait<u32> for S {}
+
+fn foo<T: Trait<U>, U>(t: T) -> U {}
+
+fn test(s: S) {
+    foo(s)<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn obligation_from_method_clause() {
+    let t = type_at(
+        r#"
+//- /main.rs
+struct S;
+
+trait Trait<T> {}
+impl Trait<isize> for S {}
+
+struct O;
+impl O {
+    fn foo<T: Trait<U>, U>(&self, t: T) -> U {}
+}
+
+fn test() {
+    O.foo(S)<|>;
+}
+"#,
+    );
+    assert_eq!(t, "isize");
+}
+
+#[test]
+fn obligation_from_self_method_clause() {
+    let t = type_at(
+        r#"
+//- /main.rs
+struct S;
+
+trait Trait<T> {}
+impl Trait<i64> for S {}
+
+impl S {
+    fn foo<U>(&self) -> U where Self: Trait<U> {}
+}
+
+fn test() {
+    S.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "i64");
+}
+
+#[test]
+fn obligation_from_impl_clause() {
+    let t = type_at(
+        r#"
+//- /main.rs
+struct S;
+
+trait Trait<T> {}
+impl Trait<&str> for S {}
+
+struct O<T>;
+impl<U, T: Trait<U>> O<T> {
+    fn foo(&self) -> U {}
+}
+
+fn test(o: O<S>) {
+    o.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "&str");
+}
+
+#[test]
+fn generic_param_env_1() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Clone {}
+trait Trait { fn foo(self) -> u128; }
+struct S;
+impl Clone for S {}
+impl<T> Trait for T where T: Clone {}
+fn test<T: Clone>(t: T) { t.foo()<|>; }
+"#,
+    );
+    assert_eq!(t, "u128");
+}
+
+#[test]
+fn generic_param_env_1_not_met() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Clone {}
+trait Trait { fn foo(self) -> u128; }
+struct S;
+impl Clone for S {}
+impl<T> Trait for T where T: Clone {}
+fn test<T>(t: T) { t.foo()<|>; }
+"#,
+    );
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn generic_param_env_2() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait { fn foo(self) -> u128; }
+struct S;
+impl Trait for S {}
+fn test<T: Trait>(t: T) { t.foo()<|>; }
+"#,
+    );
+    assert_eq!(t, "u128");
+}
+
+#[test]
+fn generic_param_env_2_not_met() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait { fn foo(self) -> u128; }
+struct S;
+impl Trait for S {}
+fn test<T>(t: T) { t.foo()<|>; }
+"#,
+    );
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn generic_param_env_deref() {
+    let t = type_at(
+        r#"
+//- /main.rs
+#[lang = "deref"]
+trait Deref {
+    type Target;
+}
+trait Trait {}
+impl<T> Deref for T where T: Trait {
+    type Target = i128;
+}
+fn test<T: Trait>(t: T) { (*t)<|>; }
+"#,
+    );
+    assert_eq!(t, "i128");
+}
+
+#[test]
+fn associated_type_placeholder() {
+    let t = type_at(
+        r#"
+//- /main.rs
+pub trait ApplyL {
+    type Out;
+}
+
+pub struct RefMutL<T>;
+
+impl<T> ApplyL for RefMutL<T> {
+    type Out = <T as ApplyL>::Out;
+}
+
+fn test<T: ApplyL>() {
+    let y: <RefMutL<T> as ApplyL>::Out = no_matter;
+    y<|>;
+}
+"#,
+    );
+    // inside the generic function, the associated type gets normalized to a placeholder `ApplL::Out<T>` [https://rust-lang.github.io/rustc-guide/traits/associated-types.html#placeholder-associated-types].
+    // FIXME: fix type parameter names going missing when going through Chalk
+    assert_eq!(t, "ApplyL::Out<[missing name]>");
+}
+
+#[test]
+fn associated_type_placeholder_2() {
+    let t = type_at(
+        r#"
+//- /main.rs
+pub trait ApplyL {
+    type Out;
+}
+fn foo<T: ApplyL>(t: T) -> <T as ApplyL>::Out;
+
+fn test<T: ApplyL>(t: T) {
+    let y = foo(t);
+    y<|>;
+}
+"#,
+    );
+    // FIXME here Chalk doesn't normalize the type to a placeholder. I think we
+    // need to add a rule like Normalize(<T as ApplyL>::Out -> ApplyL::Out<T>)
+    // to the trait env ourselves here; probably Chalk can't do this by itself.
+    // assert_eq!(t, "ApplyL::Out<[missing name]>");
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn impl_trait() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait<T> {
+    fn foo(&self) -> T;
+    fn foo2(&self) -> i64;
+}
+fn bar() -> impl Trait<u64> {}
+
+fn test(x: impl Trait<u64>, y: &impl Trait<u64>) {
+    x;
+    y;
+    let z = bar();
+    x.foo();
+    y.foo();
+    z.foo();
+    x.foo2();
+    y.foo2();
+    z.foo2();
+}
+"#),
+        @r###"
+    [30; 34) 'self': &Self
+    [55; 59) 'self': &Self
+    [99; 101) '{}': ()
+    [111; 112) 'x': impl Trait<u64>
+    [131; 132) 'y': &impl Trait<u64>
+    [152; 269) '{     ...2(); }': ()
+    [158; 159) 'x': impl Trait<u64>
+    [165; 166) 'y': &impl Trait<u64>
+    [176; 177) 'z': impl Trait<u64>
+    [180; 183) 'bar': fn bar() -> impl Trait<u64>
+    [180; 185) 'bar()': impl Trait<u64>
+    [191; 192) 'x': impl Trait<u64>
+    [191; 198) 'x.foo()': u64
+    [204; 205) 'y': &impl Trait<u64>
+    [204; 211) 'y.foo()': u64
+    [217; 218) 'z': impl Trait<u64>
+    [217; 224) 'z.foo()': u64
+    [230; 231) 'x': impl Trait<u64>
+    [230; 238) 'x.foo2()': i64
+    [244; 245) 'y': &impl Trait<u64>
+    [244; 252) 'y.foo2()': i64
+    [258; 259) 'z': impl Trait<u64>
+    [258; 266) 'z.foo2()': i64
+    "###
+    );
+}
+
+#[test]
+fn dyn_trait() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait<T> {
+    fn foo(&self) -> T;
+    fn foo2(&self) -> i64;
+}
+fn bar() -> dyn Trait<u64> {}
+
+fn test(x: dyn Trait<u64>, y: &dyn Trait<u64>) {
+    x;
+    y;
+    let z = bar();
+    x.foo();
+    y.foo();
+    z.foo();
+    x.foo2();
+    y.foo2();
+    z.foo2();
+}
+"#),
+        @r###"
+    [30; 34) 'self': &Self
+    [55; 59) 'self': &Self
+    [98; 100) '{}': ()
+    [110; 111) 'x': dyn Trait<u64>
+    [129; 130) 'y': &dyn Trait<u64>
+    [149; 266) '{     ...2(); }': ()
+    [155; 156) 'x': dyn Trait<u64>
+    [162; 163) 'y': &dyn Trait<u64>
+    [173; 174) 'z': dyn Trait<u64>
+    [177; 180) 'bar': fn bar() -> dyn Trait<u64>
+    [177; 182) 'bar()': dyn Trait<u64>
+    [188; 189) 'x': dyn Trait<u64>
+    [188; 195) 'x.foo()': u64
+    [201; 202) 'y': &dyn Trait<u64>
+    [201; 208) 'y.foo()': u64
+    [214; 215) 'z': dyn Trait<u64>
+    [214; 221) 'z.foo()': u64
+    [227; 228) 'x': dyn Trait<u64>
+    [227; 235) 'x.foo2()': i64
+    [241; 242) 'y': &dyn Trait<u64>
+    [241; 249) 'y.foo2()': i64
+    [255; 256) 'z': dyn Trait<u64>
+    [255; 263) 'z.foo2()': i64
+    "###
+    );
+}
+
+#[test]
+fn dyn_trait_bare() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait {
+    fn foo(&self) -> u64;
+}
+fn bar() -> Trait {}
+
+fn test(x: Trait, y: &Trait) -> u64 {
+    x;
+    y;
+    let z = bar();
+    x.foo();
+    y.foo();
+    z.foo();
+}
+"#),
+        @r###"
+    [27; 31) 'self': &Self
+    [61; 63) '{}': ()
+    [73; 74) 'x': dyn Trait
+    [83; 84) 'y': &dyn Trait
+    [101; 176) '{     ...o(); }': ()
+    [107; 108) 'x': dyn Trait
+    [114; 115) 'y': &dyn Trait
+    [125; 126) 'z': dyn Trait
+    [129; 132) 'bar': fn bar() -> dyn Trait
+    [129; 134) 'bar()': dyn Trait
+    [140; 141) 'x': dyn Trait
+    [140; 147) 'x.foo()': u64
+    [153; 154) 'y': &dyn Trait
+    [153; 160) 'y.foo()': u64
+    [166; 167) 'z': dyn Trait
+    [166; 173) 'z.foo()': u64
+    "###
+    );
+}
+
+#[test]
+fn weird_bounds() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait {}
+fn test() {
+    let a: impl Trait + 'lifetime = foo;
+    let b: impl 'lifetime = foo;
+    let b: impl (Trait) = foo;
+    let b: impl ('lifetime) = foo;
+    let d: impl ?Sized = foo;
+    let e: impl Trait + ?Sized = foo;
+}
+"#),
+        @r###"
+    [26; 237) '{     ...foo; }': ()
+    [36; 37) 'a': impl Trait + {error}
+    [64; 67) 'foo': impl Trait + {error}
+    [77; 78) 'b': impl {error}
+    [97; 100) 'foo': impl {error}
+    [110; 111) 'b': impl Trait
+    [128; 131) 'foo': impl Trait
+    [141; 142) 'b': impl {error}
+    [163; 166) 'foo': impl {error}
+    [176; 177) 'd': impl {error}
+    [193; 196) 'foo': impl {error}
+    [206; 207) 'e': impl Trait + {error}
+    [231; 234) 'foo': impl Trait + {error}
+    "###
+    );
+}
+
+#[test]
+fn error_bound_chalk() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait {
+    fn foo(&self) -> u32 {}
+}
+
+fn test(x: (impl Trait + UnknownTrait)) {
+    x.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn assoc_type_bindings() {
+    assert_snapshot!(
+        infer(r#"
+trait Trait {
+    type Type;
+}
+
+fn get<T: Trait>(t: T) -> <T as Trait>::Type {}
+fn get2<U, T: Trait<Type = U>>(t: T) -> U {}
+fn set<T: Trait<Type = u64>>(t: T) -> T {t}
+
+struct S<T>;
+impl<T> Trait for S<T> { type Type = T; }
+
+fn test<T: Trait<Type = u32>>(x: T, y: impl Trait<Type = i64>) {
+    get(x);
+    get2(x);
+    get(y);
+    get2(y);
+    get(set(S));
+    get2(set(S));
+    get2(S::<str>);
+}
+"#),
+        @r###"
+    [50; 51) 't': T
+    [78; 80) '{}': ()
+    [112; 113) 't': T
+    [123; 125) '{}': ()
+    [155; 156) 't': T
+    [166; 169) '{t}': T
+    [167; 168) 't': T
+    [257; 258) 'x': T
+    [263; 264) 'y': impl Trait<Type = i64>
+    [290; 398) '{     ...r>); }': ()
+    [296; 299) 'get': fn get<T>(T) -> <T as Trait>::Type
+    [296; 302) 'get(x)': {unknown}
+    [300; 301) 'x': T
+    [308; 312) 'get2': fn get2<{unknown}, T>(T) -> U
+    [308; 315) 'get2(x)': {unknown}
+    [313; 314) 'x': T
+    [321; 324) 'get': fn get<impl Trait<Type = i64>>(T) -> <T as Trait>::Type
+    [321; 327) 'get(y)': {unknown}
+    [325; 326) 'y': impl Trait<Type = i64>
+    [333; 337) 'get2': fn get2<{unknown}, impl Trait<Type = i64>>(T) -> U
+    [333; 340) 'get2(y)': {unknown}
+    [338; 339) 'y': impl Trait<Type = i64>
+    [346; 349) 'get': fn get<S<u64>>(T) -> <T as Trait>::Type
+    [346; 357) 'get(set(S))': u64
+    [350; 353) 'set': fn set<S<u64>>(T) -> T
+    [350; 356) 'set(S)': S<u64>
+    [354; 355) 'S': S<u64>
+    [363; 367) 'get2': fn get2<u64, S<u64>>(T) -> U
+    [363; 375) 'get2(set(S))': u64
+    [368; 371) 'set': fn set<S<u64>>(T) -> T
+    [368; 374) 'set(S)': S<u64>
+    [372; 373) 'S': S<u64>
+    [381; 385) 'get2': fn get2<str, S<str>>(T) -> U
+    [381; 395) 'get2(S::<str>)': str
+    [386; 394) 'S::<str>': S<str>
+    "###
+    );
+}
+
+#[test]
+fn impl_trait_assoc_binding_projection_bug() {
+    let (db, pos) = TestDB::with_position(
+        r#"
+//- /main.rs crate:main deps:std
+pub trait Language {
+    type Kind;
+}
+pub enum RustLanguage {}
+impl Language for RustLanguage {
+    type Kind = SyntaxKind;
+}
+struct SyntaxNode<L> {}
+fn foo() -> impl Iterator<Item = SyntaxNode<RustLanguage>> {}
+
+trait Clone {
+    fn clone(&self) -> Self;
+}
+
+fn api_walkthrough() {
+    for node in foo() {
+        node.clone()<|>;
+    }
+}
+
+//- /std.rs crate:std
+#[prelude_import] use iter::*;
+mod iter {
+    trait IntoIterator {
+        type Item;
+    }
+    trait Iterator {
+        type Item;
+    }
+    impl<T: Iterator> IntoIterator for T {
+        type Item = <T as Iterator>::Item;
+    }
+}
+"#,
+    );
+    assert_eq!("{unknown}", type_at_pos(&db, pos));
+}
+
+#[test]
+fn projection_eq_within_chalk() {
+    // std::env::set_var("CHALK_DEBUG", "1");
+    assert_snapshot!(
+        infer(r#"
+trait Trait1 {
+    type Type;
+}
+trait Trait2<T> {
+    fn foo(self) -> T;
+}
+impl<T, U> Trait2<T> for U where U: Trait1<Type = T> {}
+
+fn test<T: Trait1<Type = u32>>(x: T) {
+    x.foo();
+}
+"#),
+        @r###"
+    [62; 66) 'self': Self
+    [164; 165) 'x': T
+    [170; 186) '{     ...o(); }': ()
+    [176; 177) 'x': T
+    [176; 183) 'x.foo()': {unknown}
+    "###
+    );
+}
+
+#[test]
+fn where_clause_trait_in_scope_for_method_resolution() {
+    let t = type_at(
+        r#"
+//- /main.rs
+mod foo {
+    trait Trait {
+        fn foo(&self) -> u32 {}
+    }
+}
+
+fn test<T: foo::Trait>(x: T) {
+    x.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn super_trait_method_resolution() {
+    assert_snapshot!(
+        infer(r#"
+mod foo {
+    trait SuperTrait {
+        fn foo(&self) -> u32 {}
+    }
+}
+trait Trait1: foo::SuperTrait {}
+trait Trait2 where Self: foo::SuperTrait {}
+
+fn test<T: Trait1, U: Trait2>(x: T, y: U) {
+    x.foo();
+    y.foo();
+}
+"#),
+        @r###"
+    [50; 54) 'self': &Self
+    [63; 65) '{}': ()
+    [182; 183) 'x': T
+    [188; 189) 'y': U
+    [194; 223) '{     ...o(); }': ()
+    [200; 201) 'x': T
+    [200; 207) 'x.foo()': u32
+    [213; 214) 'y': U
+    [213; 220) 'y.foo()': u32
+    "###
+    );
+}
+
+#[test]
+fn super_trait_cycle() {
+    // This just needs to not crash
+    assert_snapshot!(
+        infer(r#"
+trait A: B {}
+trait B: A {}
+
+fn test<T: A>(x: T) {
+    x.foo();
+}
+"#),
+        @r###"
+    [44; 45) 'x': T
+    [50; 66) '{     ...o(); }': ()
+    [56; 57) 'x': T
+    [56; 63) 'x.foo()': {unknown}
+    "###
+    );
+}
+
+#[test]
+fn super_trait_assoc_type_bounds() {
+    assert_snapshot!(
+        infer(r#"
+trait SuperTrait { type Type; }
+trait Trait where Self: SuperTrait {}
+
+fn get2<U, T: Trait<Type = U>>(t: T) -> U {}
+fn set<T: Trait<Type = u64>>(t: T) -> T {t}
+
+struct S<T>;
+impl<T> SuperTrait for S<T> { type Type = T; }
+impl<T> Trait for S<T> {}
+
+fn test() {
+    get2(set(S));
+}
+"#),
+        @r###"
+    [103; 104) 't': T
+    [114; 116) '{}': ()
+    [146; 147) 't': T
+    [157; 160) '{t}': T
+    [158; 159) 't': T
+    [259; 280) '{     ...S)); }': ()
+    [265; 269) 'get2': fn get2<u64, S<u64>>(T) -> U
+    [265; 277) 'get2(set(S))': u64
+    [270; 273) 'set': fn set<S<u64>>(T) -> T
+    [270; 276) 'set(S)': S<u64>
+    [274; 275) 'S': S<u64>
+    "###
+    );
+}
+
+#[test]
+fn fn_trait() {
+    assert_snapshot!(
+        infer(r#"
+trait FnOnce<Args> {
+    type Output;
+
+    fn call_once(self, args: Args) -> <Self as FnOnce<Args>>::Output;
+}
+
+fn test<F: FnOnce(u32, u64) -> u128>(f: F) {
+    f.call_once((1, 2));
+}
+"#),
+        @r###"
+    [57; 61) 'self': Self
+    [63; 67) 'args': Args
+    [150; 151) 'f': F
+    [156; 184) '{     ...2)); }': ()
+    [162; 163) 'f': F
+    [162; 181) 'f.call...1, 2))': {unknown}
+    [174; 180) '(1, 2)': (u32, u64)
+    [175; 176) '1': u32
+    [178; 179) '2': u64
+    "###
+    );
+}
+
+#[test]
+fn closure_1() {
+    assert_snapshot!(
+        infer(r#"
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
+
+enum Option<T> { Some(T), None }
+impl<T> Option<T> {
+    fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Option<U> {}
+}
+
+fn test() {
+    let x = Option::Some(1u32);
+    x.map(|v| v + 1);
+    x.map(|_v| 1u64);
+    let y: Option<i64> = x.map(|_v| 1);
+}
+"#),
+        @r###"
+    [148; 152) 'self': Option<T>
+    [154; 155) 'f': F
+    [173; 175) '{}': ()
+    [189; 308) '{     ... 1); }': ()
+    [199; 200) 'x': Option<u32>
+    [203; 215) 'Option::Some': Some<u32>(T) -> Option<T>
+    [203; 221) 'Option...(1u32)': Option<u32>
+    [216; 220) '1u32': u32
+    [227; 228) 'x': Option<u32>
+    [227; 243) 'x.map(...v + 1)': Option<u32>
+    [233; 242) '|v| v + 1': |u32| -> u32
+    [234; 235) 'v': u32
+    [237; 238) 'v': u32
+    [237; 242) 'v + 1': u32
+    [241; 242) '1': u32
+    [249; 250) 'x': Option<u32>
+    [249; 265) 'x.map(... 1u64)': Option<u64>
+    [255; 264) '|_v| 1u64': |u32| -> u64
+    [256; 258) '_v': u32
+    [260; 264) '1u64': u64
+    [275; 276) 'y': Option<i64>
+    [292; 293) 'x': Option<u32>
+    [292; 305) 'x.map(|_v| 1)': Option<i64>
+    [298; 304) '|_v| 1': |u32| -> i64
+    [299; 301) '_v': u32
+    [303; 304) '1': i64
+    "###
+    );
+}
+
+#[test]
+fn closure_2() {
+    assert_snapshot!(
+        infer(r#"
+trait FnOnce<Args> {
+    type Output;
+}
+
+fn test<F: FnOnce(u32) -> u64>(f: F) {
+    f(1);
+    let g = |v| v + 1;
+    g(1u64);
+    let h = |v| 1u128 + v;
+}
+"#),
+        @r###"
+    [73; 74) 'f': F
+    [79; 155) '{     ...+ v; }': ()
+    [85; 86) 'f': F
+    [85; 89) 'f(1)': {unknown}
+    [87; 88) '1': i32
+    [99; 100) 'g': |u64| -> i32
+    [103; 112) '|v| v + 1': |u64| -> i32
+    [104; 105) 'v': u64
+    [107; 108) 'v': u64
+    [107; 112) 'v + 1': i32
+    [111; 112) '1': i32
+    [118; 119) 'g': |u64| -> i32
+    [118; 125) 'g(1u64)': i32
+    [120; 124) '1u64': u64
+    [135; 136) 'h': |u128| -> u128
+    [139; 152) '|v| 1u128 + v': |u128| -> u128
+    [140; 141) 'v': u128
+    [143; 148) '1u128': u128
+    [143; 152) '1u128 + v': u128
+    [151; 152) 'v': u128
+    "###
+    );
+}
+
+#[test]
+fn closure_as_argument_inference_order() {
+    assert_snapshot!(
+        infer(r#"
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
+
+fn foo1<T, U, F: FnOnce(T) -> U>(x: T, f: F) -> U {}
+fn foo2<T, U, F: FnOnce(T) -> U>(f: F, x: T) -> U {}
+
+struct S;
+impl S {
+    fn method(self) -> u64;
+
+    fn foo1<T, U, F: FnOnce(T) -> U>(self, x: T, f: F) -> U {}
+    fn foo2<T, U, F: FnOnce(T) -> U>(self, f: F, x: T) -> U {}
+}
+
+fn test() {
+    let x1 = foo1(S, |s| s.method());
+    let x2 = foo2(|s| s.method(), S);
+    let x3 = S.foo1(S, |s| s.method());
+    let x4 = S.foo2(|s| s.method(), S);
+}
+"#),
+        @r###"
+    [95; 96) 'x': T
+    [101; 102) 'f': F
+    [112; 114) '{}': ()
+    [148; 149) 'f': F
+    [154; 155) 'x': T
+    [165; 167) '{}': ()
+    [202; 206) 'self': S
+    [254; 258) 'self': S
+    [260; 261) 'x': T
+    [266; 267) 'f': F
+    [277; 279) '{}': ()
+    [317; 321) 'self': S
+    [323; 324) 'f': F
+    [329; 330) 'x': T
+    [340; 342) '{}': ()
+    [356; 515) '{     ... S); }': ()
+    [366; 368) 'x1': u64
+    [371; 375) 'foo1': fn foo1<S, u64, |S| -> u64>(T, F) -> U
+    [371; 394) 'foo1(S...hod())': u64
+    [376; 377) 'S': S
+    [379; 393) '|s| s.method()': |S| -> u64
+    [380; 381) 's': S
+    [383; 384) 's': S
+    [383; 393) 's.method()': u64
+    [404; 406) 'x2': u64
+    [409; 413) 'foo2': fn foo2<S, u64, |S| -> u64>(F, T) -> U
+    [409; 432) 'foo2(|...(), S)': u64
+    [414; 428) '|s| s.method()': |S| -> u64
+    [415; 416) 's': S
+    [418; 419) 's': S
+    [418; 428) 's.method()': u64
+    [430; 431) 'S': S
+    [442; 444) 'x3': u64
+    [447; 448) 'S': S
+    [447; 472) 'S.foo1...hod())': u64
+    [454; 455) 'S': S
+    [457; 471) '|s| s.method()': |S| -> u64
+    [458; 459) 's': S
+    [461; 462) 's': S
+    [461; 471) 's.method()': u64
+    [482; 484) 'x4': u64
+    [487; 488) 'S': S
+    [487; 512) 'S.foo2...(), S)': u64
+    [494; 508) '|s| s.method()': |S| -> u64
+    [495; 496) 's': S
+    [498; 499) 's': S
+    [498; 508) 's.method()': u64
+    [510; 511) 'S': S
+    "###
+    );
+}
+
+#[test]
+fn unselected_projection_in_trait_env_1() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait {
+    type Item;
+}
+
+trait Trait2 {
+    fn foo(&self) -> u32;
+}
+
+fn test<T: Trait>() where T::Item: Trait2 {
+    let x: T::Item = no_matter;
+    x.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn unselected_projection_in_trait_env_2() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait<T> {
+    type Item;
+}
+
+trait Trait2 {
+    fn foo(&self) -> u32;
+}
+
+fn test<T, U>() where T::Item: Trait2, T: Trait<U::Item>, U: Trait<()> {
+    let x: T::Item = no_matter;
+    x.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "u32");
+}
+
+#[test]
+fn trait_impl_self_ty() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait<T> {
+   fn foo(&self);
+}
+
+struct S;
+
+impl Trait<Self> for S {}
+
+fn test() {
+    S.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "()");
+}
+
+#[test]
+fn trait_impl_self_ty_cycle() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait {
+   fn foo(&self);
+}
+
+struct S<T>;
+
+impl Trait for S<Self> {}
+
+fn test() {
+    S.foo()<|>;
+}
+"#,
+    );
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn unselected_projection_in_trait_env_cycle_1() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait {
+    type Item;
+}
+
+trait Trait2<T> {}
+
+fn test<T: Trait>() where T: Trait2<T::Item> {
+    let x: T::Item = no_matter<|>;
+}
+"#,
+    );
+    // this is a legitimate cycle
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn unselected_projection_in_trait_env_cycle_2() {
+    let t = type_at(
+        r#"
+//- /main.rs
+trait Trait<T> {
+    type Item;
+}
+
+fn test<T, U>() where T: Trait<U::Item>, U: Trait<T::Item> {
+    let x: T::Item = no_matter<|>;
+}
+"#,
+    );
+    // this is a legitimate cycle
+    assert_eq!(t, "{unknown}");
+}
+
+#[test]
+fn unify_impl_trait() {
+    covers!(insert_vars_for_impl_trait);
+    assert_snapshot!(
+        infer_with_mismatches(r#"
+trait Trait<T> {}
+
+fn foo(x: impl Trait<u32>) { loop {} }
+fn bar<T>(x: impl Trait<T>) -> T { loop {} }
+
+struct S<T>(T);
+impl<T> Trait<T> for S<T> {}
+
+fn default<T>() -> T { loop {} }
+
+fn test() -> impl Trait<i32> {
+    let s1 = S(default());
+    foo(s1);
+    let x: i32 = bar(S(default()));
+    S(default())
+}
+"#, true),
+        @r###"
+    [27; 28) 'x': impl Trait<u32>
+    [47; 58) '{ loop {} }': ()
+    [49; 56) 'loop {}': !
+    [54; 56) '{}': ()
+    [69; 70) 'x': impl Trait<T>
+    [92; 103) '{ loop {} }': T
+    [94; 101) 'loop {}': !
+    [99; 101) '{}': ()
+    [172; 183) '{ loop {} }': T
+    [174; 181) 'loop {}': !
+    [179; 181) '{}': ()
+    [214; 310) '{     ...t()) }': S<i32>
+    [224; 226) 's1': S<u32>
+    [229; 230) 'S': S<u32>(T) -> S<T>
+    [229; 241) 'S(default())': S<u32>
+    [231; 238) 'default': fn default<u32>() -> T
+    [231; 240) 'default()': u32
+    [247; 250) 'foo': fn foo(impl Trait<u32>) -> ()
+    [247; 254) 'foo(s1)': ()
+    [251; 253) 's1': S<u32>
+    [264; 265) 'x': i32
+    [273; 276) 'bar': fn bar<i32>(impl Trait<T>) -> T
+    [273; 290) 'bar(S(...lt()))': i32
+    [277; 278) 'S': S<i32>(T) -> S<T>
+    [277; 289) 'S(default())': S<i32>
+    [279; 286) 'default': fn default<i32>() -> T
+    [279; 288) 'default()': i32
+    [296; 297) 'S': S<i32>(T) -> S<T>
+    [296; 308) 'S(default())': S<i32>
+    [298; 305) 'default': fn default<i32>() -> T
+    [298; 307) 'default()': i32
+    "###
+    );
+}