6 files changed, 131 insertions, 165 deletions

diff --git a/crates/base_db/src/fixture.rs b/crates/base_db/src/fixture.rs
index d56b20b83..d0c946d83 100644
--- a/crates/base_db/src/fixture.rs
+++ b/crates/base_db/src/fixture.rs
@@ -114,6 +114,9 @@ impl ChangeFixture {
 
             let meta = FileMeta::from(entry);
             assert!(meta.path.starts_with(&source_root_prefix));
+            if !meta.deps.is_empty() {
+                assert!(meta.krate.is_some(), "can't specify deps without naming the crate")
+            }
 
             if meta.introduce_new_source_root {
                 roots.push(SourceRoot::new_local(mem::take(&mut file_set)));
@@ -199,6 +202,7 @@ impl ChangeFixture {
     }
 }
 
+#[derive(Debug)]
 struct FileMeta {
     path: String,
     krate: Option<String>,
diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index 94b628fb8..0f418ea49 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -792,6 +792,7 @@ fn issue_4800() {
 fn issue_4966() {
     check_infer(
         r#"
+        //- minicore: deref
         pub trait IntoIterator {
             type Item;
         }
@@ -802,12 +803,7 @@ fn issue_4966() {
 
         struct Vec<T> {}
 
-        #[lang = "deref"]
-        pub trait Deref {
-            type Target;
-        }
-
-        impl<T> Deref for Vec<T> {
+        impl<T> core::ops::Deref for Vec<T> {
             type Target = [T];
         }
 
@@ -824,23 +820,23 @@ fn issue_4966() {
         }
         "#,
         expect![[r#"
-            270..274 'iter': T
-            289..291 '{}': ()
-            303..447 '{     ...r(); }': ()
-            313..318 'inner': Map<|&f64| -> f64>
-            321..345 'Map { ... 0.0 }': Map<|&f64| -> f64>
-            330..343 '|_: &f64| 0.0': |&f64| -> f64
-            331..332 '_': &f64
-            340..343 '0.0': f64
-            356..362 'repeat': Repeat<Map<|&f64| -> f64>>
-            365..390 'Repeat...nner }': Repeat<Map<|&f64| -> f64>>
-            383..388 'inner': Map<|&f64| -> f64>
-            401..404 'vec': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            407..416 'from_iter': fn from_iter<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>, Repeat<Map<|&f64| -> f64>>>(Repeat<Map<|&f64| -> f64>>) -> Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            407..424 'from_i...epeat)': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            417..423 'repeat': Repeat<Map<|&f64| -> f64>>
-            431..434 'vec': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
-            431..444 'vec.foo_bar()': {unknown}
+            225..229 'iter': T
+            244..246 '{}': ()
+            258..402 '{     ...r(); }': ()
+            268..273 'inner': Map<|&f64| -> f64>
+            276..300 'Map { ... 0.0 }': Map<|&f64| -> f64>
+            285..298 '|_: &f64| 0.0': |&f64| -> f64
+            286..287 '_': &f64
+            295..298 '0.0': f64
+            311..317 'repeat': Repeat<Map<|&f64| -> f64>>
+            320..345 'Repeat...nner }': Repeat<Map<|&f64| -> f64>>
+            338..343 'inner': Map<|&f64| -> f64>
+            356..359 'vec': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
+            362..371 'from_iter': fn from_iter<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>, Repeat<Map<|&f64| -> f64>>>(Repeat<Map<|&f64| -> f64>>) -> Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
+            362..379 'from_i...epeat)': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
+            372..378 'repeat': Repeat<Map<|&f64| -> f64>>
+            386..389 'vec': Vec<IntoIterator::Item<Repeat<Map<|&f64| -> f64>>>>
+            386..399 'vec.foo_bar()': {unknown}
         "#]],
     );
 }
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index dd1ea817f..279a1354a 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -567,11 +567,11 @@ fn indexing_arrays() {
 fn infer_ops_index() {
     check_types(
         r#"
-//- /main.rs crate:main deps:std
+//- minicore: index
 struct Bar;
 struct Foo;
 
-impl std::ops::Index<u32> for Bar {
+impl core::ops::Index<u32> for Bar {
     type Output = Foo;
 }
 
@@ -580,15 +580,6 @@ fn test() {
     let b = a[1u32];
     b;
 } //^ Foo
-
-//- /std.rs crate:std
-#[prelude_import] use ops::*;
-mod ops {
-    #[lang = "index"]
-    pub trait Index<Idx> {
-        type Output;
-    }
-}
 "#,
     );
 }
@@ -597,16 +588,16 @@ mod ops {
 fn infer_ops_index_int() {
     check_types(
         r#"
-//- /main.rs crate:main deps:std
+//- minicore: index
 struct Bar;
 struct Foo;
 
-impl std::ops::Index<u32> for Bar {
+impl core::ops::Index<u32> for Bar {
     type Output = Foo;
 }
 
 struct Range;
-impl std::ops::Index<Range> for Bar {
+impl core::ops::Index<Range> for Bar {
     type Output = Bar;
 }
 
@@ -616,15 +607,6 @@ fn test() {
     b;
   //^ Foo
 }
-
-//- /std.rs crate:std
-#[prelude_import] use ops::*;
-mod ops {
-    #[lang = "index"]
-    pub trait Index<Idx> {
-        type Output;
-    }
-}
 "#,
     );
 }
@@ -633,25 +615,12 @@ mod ops {
 fn infer_ops_index_autoderef() {
     check_types(
         r#"
-//- /main.rs crate:main deps:std
+//- minicore: index, slice
 fn test() {
     let a = &[1u32, 2, 3];
-    let b = a[1u32];
+    let b = a[1];
     b;
 } //^ u32
-
-//- /std.rs crate:std
-impl<T> ops::Index<u32> for [T] {
-    type Output = T;
-}
-
-#[prelude_import] use ops::*;
-mod ops {
-    #[lang = "index"]
-    pub trait Index<Idx> {
-        type Output;
-    }
-}
 "#,
     );
 }
@@ -884,12 +853,9 @@ fn test<T>(t: T) { t.foo(); }
 fn generic_param_env_deref() {
     check_types(
         r#"
-#[lang = "deref"]
-trait Deref {
-    type Target;
-}
+//- minicore: deref
 trait Trait {}
-impl<T> Deref for T where T: Trait {
+impl<T> core::ops::Deref for T where T: Trait {
     type Target = i128;
 }
 fn test<T: Trait>(t: T) { (*t); }
@@ -1758,20 +1724,7 @@ fn test() {
 fn fn_trait_deref_with_ty_default() {
     check_infer(
         r#"
-#[lang = "deref"]
-trait Deref {
-    type Target;
-
-    fn deref(&self) -> &Self::Target;
-}
-
-#[lang="fn_once"]
-trait FnOnce<Args> {
-    type Output;
-
-    fn call_once(self, args: Args) -> Self::Output;
-}
-
+//- minicore: deref, fn
 struct Foo;
 
 impl Foo {
@@ -1784,7 +1737,7 @@ impl<T, F> Lazy<T, F> {
     pub fn new(f: F) -> Lazy<T, F> {}
 }
 
-impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
+impl<T, F: FnOnce() -> T> core::ops::Deref for Lazy<T, F> {
     type Target = T;
 }
 
@@ -1798,32 +1751,29 @@ fn test() {
     let r2 = lazy2.foo();
 }"#,
         expect![[r#"
-            64..68 'self': &Self
-            165..169 'self': Self
-            171..175 'args': Args
-            239..243 'self': &Foo
-            254..256 '{}': ()
-            334..335 'f': F
-            354..356 '{}': ()
-            443..689 '{     ...o(); }': ()
-            453..458 'lazy1': Lazy<Foo, || -> Foo>
-            475..484 'Lazy::new': fn new<Foo, || -> Foo>(|| -> Foo) -> Lazy<Foo, || -> Foo>
-            475..492 'Lazy::...| Foo)': Lazy<Foo, || -> Foo>
-            485..491 '|| Foo': || -> Foo
-            488..491 'Foo': Foo
-            502..504 'r1': usize
-            507..512 'lazy1': Lazy<Foo, || -> Foo>
-            507..518 'lazy1.foo()': usize
-            560..575 'make_foo_fn_ptr': fn() -> Foo
-            591..602 'make_foo_fn': fn make_foo_fn() -> Foo
-            612..617 'lazy2': Lazy<Foo, fn() -> Foo>
-            634..643 'Lazy::new': fn new<Foo, fn() -> Foo>(fn() -> Foo) -> Lazy<Foo, fn() -> Foo>
-            634..660 'Lazy::...n_ptr)': Lazy<Foo, fn() -> Foo>
-            644..659 'make_foo_fn_ptr': fn() -> Foo
-            670..672 'r2': usize
-            675..680 'lazy2': Lazy<Foo, fn() -> Foo>
-            675..686 'lazy2.foo()': usize
-            549..551 '{}': ()
+            36..40 'self': &Foo
+            51..53 '{}': ()
+            131..132 'f': F
+            151..153 '{}': ()
+            251..497 '{     ...o(); }': ()
+            261..266 'lazy1': Lazy<Foo, || -> Foo>
+            283..292 'Lazy::new': fn new<Foo, || -> Foo>(|| -> Foo) -> Lazy<Foo, || -> Foo>
+            283..300 'Lazy::...| Foo)': Lazy<Foo, || -> Foo>
+            293..299 '|| Foo': || -> Foo
+            296..299 'Foo': Foo
+            310..312 'r1': usize
+            315..320 'lazy1': Lazy<Foo, || -> Foo>
+            315..326 'lazy1.foo()': usize
+            368..383 'make_foo_fn_ptr': fn() -> Foo
+            399..410 'make_foo_fn': fn make_foo_fn() -> Foo
+            420..425 'lazy2': Lazy<Foo, fn() -> Foo>
+            442..451 'Lazy::new': fn new<Foo, fn() -> Foo>(fn() -> Foo) -> Lazy<Foo, fn() -> Foo>
+            442..468 'Lazy::...n_ptr)': Lazy<Foo, fn() -> Foo>
+            452..467 'make_foo_fn_ptr': fn() -> Foo
+            478..480 'r2': usize
+            483..488 'lazy2': Lazy<Foo, fn() -> Foo>
+            483..494 'lazy2.foo()': usize
+            357..359 '{}': ()
         "#]],
     );
 }
@@ -2972,28 +2922,13 @@ fn infer_box_fn_arg() {
     // The type mismatch is because we don't define Unsize and CoerceUnsized
     check_infer_with_mismatches(
         r#"
-//- /lib.rs deps:std
-
-#[lang = "fn_once"]
-pub trait FnOnce<Args> {
-    type Output;
-
-    extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
-}
-
-#[lang = "deref"]
-pub trait Deref {
-    type Target: ?Sized;
-
-    fn deref(&self) -> &Self::Target;
-}
-
+//- minicore: fn, deref, option
 #[lang = "owned_box"]
 pub struct Box<T: ?Sized> {
     inner: *mut T,
 }
 
-impl<T: ?Sized> Deref for Box<T> {
+impl<T: ?Sized> core::ops::Deref for Box<T> {
     type Target = T;
 
     fn deref(&self) -> &T {
@@ -3001,38 +2936,30 @@ impl<T: ?Sized> Deref for Box<T> {
     }
 }
 
-enum Option<T> {
-    None,
-    Some(T)
-}
-
 fn foo() {
-    let s = Option::None;
+    let s = None;
     let f: Box<dyn FnOnce(&Option<i32>)> = box (|ps| {});
     f(&s);
 }"#,
         expect![[r#"
-            100..104 'self': Self
-            106..110 'args': Args
-            214..218 'self': &Self
-            384..388 'self': &Box<T>
-            396..423 '{     ...     }': &T
-            406..417 '&self.inner': &*mut T
-            407..411 'self': &Box<T>
-            407..417 'self.inner': *mut T
-            478..576 '{     ...&s); }': ()
-            488..489 's': Option<i32>
-            492..504 'Option::None': Option<i32>
-            514..515 'f': Box<dyn FnOnce(&Option<i32>)>
-            549..562 'box (|ps| {})': Box<|{unknown}| -> ()>
-            554..561 '|ps| {}': |{unknown}| -> ()
-            555..557 'ps': {unknown}
-            559..561 '{}': ()
-            568..569 'f': Box<dyn FnOnce(&Option<i32>)>
-            568..573 'f(&s)': ()
-            570..572 '&s': &Option<i32>
-            571..572 's': Option<i32>
-            549..562: expected Box<dyn FnOnce(&Option<i32>)>, got Box<|{unknown}| -> ()>
+            154..158 'self': &Box<T>
+            166..193 '{     ...     }': &T
+            176..187 '&self.inner': &*mut T
+            177..181 'self': &Box<T>
+            177..187 'self.inner': *mut T
+            206..296 '{     ...&s); }': ()
+            216..217 's': Option<i32>
+            220..224 'None': Option<i32>
+            234..235 'f': Box<dyn FnOnce(&Option<i32>)>
+            269..282 'box (|ps| {})': Box<|{unknown}| -> ()>
+            274..281 '|ps| {}': |{unknown}| -> ()
+            275..277 'ps': {unknown}
+            279..281 '{}': ()
+            288..289 'f': Box<dyn FnOnce(&Option<i32>)>
+            288..293 'f(&s)': ()
+            290..292 '&s': &Option<i32>
+            291..292 's': Option<i32>
+            269..282: expected Box<dyn FnOnce(&Option<i32>)>, got Box<|{unknown}| -> ()>
         "#]],
     );
 }
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index 4705fae08..05a2b1293 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -3014,8 +3014,8 @@ fn foo() {
                                     file_id: FileId(
                                         1,
                                     ),
-                                    full_range: 250..432,
-                                    focus_range: 289..295,
+                                    full_range: 251..433,
+                                    focus_range: 290..296,
                                     name: "Future",
                                     kind: Trait,
                                     description: "pub trait Future",
diff --git a/crates/ide_completion/src/render.rs b/crates/ide_completion/src/render.rs
index 4b55f7504..9bec03e17 100644
--- a/crates/ide_completion/src/render.rs
+++ b/crates/ide_completion/src/render.rs
@@ -1269,16 +1269,11 @@ fn bar(t: &Foo) {}
     fn suggest_deref_fn_ret() {
         check_relevance(
             r#"
-#[lang = "deref"]
-trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
-
+//- minicore: deref
 struct S;
 struct T(S);
 
-impl Deref for T {
+impl core::ops::Deref for T {
     type Target = S;
 
     fn deref(&self) -> &Self::Target {
@@ -1292,15 +1287,16 @@ fn bar() -> T {}
 fn main() {
     foo($0);
 }
-            "#,
+"#,
             expect![[r#"
-                tt Deref []
-                fn bar() []
-                fn &bar() [type]
-                fn foo(…) []
                 st T []
                 st S []
                 fn main() []
+                fn bar() []
+                fn &bar() [type]
+                fn foo(…) []
+                md core []
+                tt Sized []
             "#]],
         )
     }
diff --git a/crates/test_utils/src/minicore.rs b/crates/test_utils/src/minicore.rs
index 769028580..71f07d38a 100644
--- a/crates/test_utils/src/minicore.rs
+++ b/crates/test_utils/src/minicore.rs
@@ -15,6 +15,7 @@
 //!     range:
 //!     deref: sized
 //!     deref_mut: deref
+//!     index: sized
 //!     fn:
 //!     pin:
 //!     future: pin
@@ -167,6 +168,48 @@ pub mod ops {
     };
     // endregion:deref
 
+    // region:index
+    mod index {
+        #[lang = "index"]
+        pub trait Index<Idx: ?Sized> {
+            type Output: ?Sized;
+            fn index(&self, index: Idx) -> &Self::Output;
+        }
+        #[lang = "index_mut"]
+        pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
+            fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
+        }
+
+        // region:slice
+        impl<T, I> Index<I> for [T]
+        where
+            I: SliceIndex<[T]>,
+        {
+            type Output = I::Output;
+            fn index(&self, index: I) -> &I::Output {
+                loop {}
+            }
+        }
+        impl<T, I> IndexMut<I> for [T]
+        where
+            I: SliceIndex<[T]>,
+        {
+            fn index_mut(&mut self, index: I) -> &mut I::Output {
+                loop {}
+            }
+        }
+
+        pub unsafe trait SliceIndex<T: ?Sized> {
+            type Output: ?Sized;
+        }
+        unsafe impl<T> SliceIndex<[T]> for usize {
+            type Output = T;
+        }
+        // endregion:slice
+    }
+    pub use self::index::{Index, IndexMut};
+    // endregion:index
+
     // region:range
     mod range {
         #[lang = "RangeFull"]