Merge #9294

9294: internal: introduce minicore -- a subset of libcore for testing r=matklad a=matklad

Clearly, we need one more fixed point iteration loop!

Co-authored-by: Aleksey Kladov <[email protected]>

13 files changed, 1149 insertions, 1027 deletions

diff --git a/crates/base_db/src/fixture.rs b/crates/base_db/src/fixture.rs
index 1b17db102..d56b20b83 100644
--- a/crates/base_db/src/fixture.rs
+++ b/crates/base_db/src/fixture.rs
@@ -9,8 +9,8 @@ use test_utils::{
 use vfs::{file_set::FileSet, VfsPath};
 
 use crate::{
-    input::CrateName, Change, CrateGraph, CrateId, Edition, Env, FileId, FilePosition, FileRange,
-    SourceDatabaseExt, SourceRoot, SourceRootId,
+    input::CrateName, Change, CrateDisplayName, CrateGraph, CrateId, Edition, Env, FileId,
+    FilePosition, FileRange, SourceDatabaseExt, SourceRoot, SourceRootId,
 };
 
 pub const WORKSPACE: SourceRootId = SourceRootId(0);
@@ -81,7 +81,7 @@ pub struct ChangeFixture {
 
 impl ChangeFixture {
     pub fn parse(ra_fixture: &str) -> ChangeFixture {
-        let fixture = Fixture::parse(ra_fixture);
+        let (mini_core, fixture) = Fixture::parse(ra_fixture);
         let mut change = Change::new();
 
         let mut files = Vec::new();
@@ -166,6 +166,31 @@ impl ChangeFixture {
             }
         }
 
+        if let Some(mini_core) = mini_core {
+            let core_file = file_id;
+            file_id.0 += 1;
+
+            let mut fs = FileSet::default();
+            fs.insert(core_file, VfsPath::new_virtual_path("/sysroot/core/lib.rs".to_string()));
+            roots.push(SourceRoot::new_library(fs));
+
+            change.change_file(core_file, Some(Arc::new(mini_core.source_code())));
+
+            let all_crates = crate_graph.crates_in_topological_order();
+
+            let core_crate = crate_graph.add_crate_root(
+                core_file,
+                Edition::Edition2021,
+                Some(CrateDisplayName::from_canonical_name("core".to_string())),
+                CfgOptions::default(),
+                Env::default(),
+                Vec::new(),
+            );
+
+            for krate in all_crates {
+                crate_graph.add_dep(krate, CrateName::new("core").unwrap(), core_crate).unwrap();
+            }
+        }
         roots.push(SourceRoot::new_local(mem::take(&mut file_set)));
         change.set_roots(roots);
         change.set_crate_graph(crate_graph);
diff --git a/crates/hir_ty/src/tests/coercion.rs b/crates/hir_ty/src/tests/coercion.rs
index 4f859fc85..713b74165 100644
--- a/crates/hir_ty/src/tests/coercion.rs
+++ b/crates/hir_ty/src/tests/coercion.rs
@@ -23,38 +23,29 @@ fn infer_block_expr_type_mismatch() {
 fn coerce_places() {
     check_infer(
         r#"
-        struct S<T> { a: T }
+//- minicore: coerce_unsized
+struct S<T> { a: T }
 
-        fn f<T>(_: &[T]) -> T { loop {} }
-        fn g<T>(_: S<&[T]>) -> T { loop {} }
+fn f<T>(_: &[T]) -> T { loop {} }
+fn g<T>(_: S<&[T]>) -> T { loop {} }
 
-        fn gen<T>() -> *mut [T; 2] { loop {} }
-        fn test1<U>() -> *mut [U] {
-            gen()
-        }
-
-        fn test2() {
-            let arr: &[u8; 1] = &[1];
-
-            let a: &[_] = arr;
-            let b = f(arr);
-            let c: &[_] = { arr };
-            let d = g(S { a: arr });
-            let e: [&[_]; 1] = [arr];
-            let f: [&[_]; 2] = [arr; 2];
-            let g: (&[_], &[_]) = (arr, arr);
-        }
+fn gen<T>() -> *mut [T; 2] { loop {} }
+fn test1<U>() -> *mut [U] {
+    gen()
+}
 
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T: ?Sized> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
+fn test2() {
+    let arr: &[u8; 1] = &[1];
 
-        impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
-        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
-        "#,
+    let a: &[_] = arr;
+    let b = f(arr);
+    let c: &[_] = { arr };
+    let d = g(S { a: arr });
+    let e: [&[_]; 1] = [arr];
+    let f: [&[_]; 2] = [arr; 2];
+    let g: (&[_], &[_]) = (arr, arr);
+}
+"#,
         expect![[r#"
             30..31 '_': &[T]
             44..55 '{ loop {} }': T
@@ -131,60 +122,52 @@ fn infer_let_stmt_coerce() {
 fn infer_custom_coerce_unsized() {
     check_infer(
         r#"
-        struct A<T: ?Sized>(*const T);
-        struct B<T: ?Sized>(*const T);
-        struct C<T: ?Sized> { inner: *const T }
+//- minicore: coerce_unsized
+use core::{marker::Unsize, ops::CoerceUnsized};
 
-        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<B<U>> for B<T> {}
-        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<C<U>> for C<T> {}
+struct A<T: ?Sized>(*const T);
+struct B<T: ?Sized>(*const T);
+struct C<T: ?Sized> { inner: *const T }
 
-        fn foo1<T>(x: A<[T]>) -> A<[T]> { x }
-        fn foo2<T>(x: B<[T]>) -> B<[T]> { x }
-        fn foo3<T>(x: C<[T]>) -> C<[T]> { x }
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<B<U>> for B<T> {}
+impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<C<U>> for C<T> {}
 
-        fn test(a: A<[u8; 2]>, b: B<[u8; 2]>, c: C<[u8; 2]>) {
-            let d = foo1(a);
-            let e = foo2(b);
-            let f = foo3(c);
-        }
-
-
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T: ?Sized> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
+fn foo1<T>(x: A<[T]>) -> A<[T]> { x }
+fn foo2<T>(x: B<[T]>) -> B<[T]> { x }
+fn foo3<T>(x: C<[T]>) -> C<[T]> { x }
 
-        impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
-        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
-        "#,
+fn test(a: A<[u8; 2]>, b: B<[u8; 2]>, c: C<[u8; 2]>) {
+    let d = foo1(a);
+    let e = foo2(b);
+    let f = foo3(c);
+}
+"#,
         expect![[r#"
-            257..258 'x': A<[T]>
-            278..283 '{ x }': A<[T]>
-            280..281 'x': A<[T]>
-            295..296 'x': B<[T]>
-            316..321 '{ x }': B<[T]>
-            318..319 'x': B<[T]>
-            333..334 'x': C<[T]>
-            354..359 '{ x }': C<[T]>
-            356..357 'x': C<[T]>
-            369..370 'a': A<[u8; 2]>
-            384..385 'b': B<[u8; 2]>
-            399..400 'c': C<[u8; 2]>
-            414..480 '{     ...(c); }': ()
-            424..425 'd': A<[{unknown}]>
-            428..432 'foo1': fn foo1<{unknown}>(A<[{unknown}]>) -> A<[{unknown}]>
-            428..435 'foo1(a)': A<[{unknown}]>
-            433..434 'a': A<[u8; 2]>
-            445..446 'e': B<[u8]>
-            449..453 'foo2': fn foo2<u8>(B<[u8]>) -> B<[u8]>
-            449..456 'foo2(b)': B<[u8]>
-            454..455 'b': B<[u8; 2]>
-            466..467 'f': C<[u8]>
-            470..474 'foo3': fn foo3<u8>(C<[u8]>) -> C<[u8]>
-            470..477 'foo3(c)': C<[u8]>
-            475..476 'c': C<[u8; 2]>
+            306..307 'x': A<[T]>
+            327..332 '{ x }': A<[T]>
+            329..330 'x': A<[T]>
+            344..345 'x': B<[T]>
+            365..370 '{ x }': B<[T]>
+            367..368 'x': B<[T]>
+            382..383 'x': C<[T]>
+            403..408 '{ x }': C<[T]>
+            405..406 'x': C<[T]>
+            418..419 'a': A<[u8; 2]>
+            433..434 'b': B<[u8; 2]>
+            448..449 'c': C<[u8; 2]>
+            463..529 '{     ...(c); }': ()
+            473..474 'd': A<[{unknown}]>
+            477..481 'foo1': fn foo1<{unknown}>(A<[{unknown}]>) -> A<[{unknown}]>
+            477..484 'foo1(a)': A<[{unknown}]>
+            482..483 'a': A<[u8; 2]>
+            494..495 'e': B<[u8]>
+            498..502 'foo2': fn foo2<u8>(B<[u8]>) -> B<[u8]>
+            498..505 'foo2(b)': B<[u8]>
+            503..504 'b': B<[u8; 2]>
+            515..516 'f': C<[u8]>
+            519..523 'foo3': fn foo3<u8>(C<[u8]>) -> C<[u8]>
+            519..526 'foo3(c)': C<[u8]>
+            524..525 'c': C<[u8; 2]>
         "#]],
     );
 }
@@ -193,21 +176,16 @@ fn infer_custom_coerce_unsized() {
 fn infer_if_coerce() {
     check_infer(
         r#"
-        fn foo<T>(x: &[T]) -> &[T] { loop {} }
-        fn test() {
-            let x = if true {
-                foo(&[1])
-            } else {
-                &[1]
-            };
-        }
-
-
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T: ?Sized> {}
-        "#,
+//- minicore: unsize
+fn foo<T>(x: &[T]) -> &[T] { loop {} }
+fn test() {
+    let x = if true {
+        foo(&[1])
+    } else {
+        &[1]
+    };
+}
+"#,
         expect![[r#"
             10..11 'x': &[T]
             27..38 '{ loop {} }': &[T]
@@ -235,25 +213,16 @@ fn infer_if_coerce() {
 fn infer_if_else_coerce() {
     check_infer(
         r#"
-        fn foo<T>(x: &[T]) -> &[T] { loop {} }
-        fn test() {
-            let x = if true {
-                &[1]
-            } else {
-                foo(&[1])
-            };
-        }
-
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T: ?Sized> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
-        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
-        "#,
+//- minicore: coerce_unsized
+fn foo<T>(x: &[T]) -> &[T] { loop {} }
+fn test() {
+    let x = if true {
+        &[1]
+    } else {
+        foo(&[1])
+    };
+}
+"#,
         expect![[r#"
             10..11 'x': &[T]
             27..38 '{ loop {} }': &[T]
@@ -281,20 +250,16 @@ fn infer_if_else_coerce() {
 fn infer_match_first_coerce() {
     check_infer(
         r#"
-        fn foo<T>(x: &[T]) -> &[T] { loop {} }
-        fn test(i: i32) {
-            let x = match i {
-                2 => foo(&[2]),
-                1 => &[1],
-                _ => &[3],
-            };
-        }
-
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T: ?Sized> {}
-        "#,
+//- minicore: unsize
+fn foo<T>(x: &[T]) -> &[T] { loop {} }
+fn test(i: i32) {
+    let x = match i {
+        2 => foo(&[2]),
+        1 => &[1],
+        _ => &[3],
+    };
+}
+"#,
         expect![[r#"
             10..11 'x': &[T]
             27..38 '{ loop {} }': &[T]
@@ -329,25 +294,16 @@ fn infer_match_first_coerce() {
 fn infer_match_second_coerce() {
     check_infer(
         r#"
-        fn foo<T>(x: &[T]) -> &[T] { loop {} }
-        fn test(i: i32) {
-            let x = match i {
-                1 => &[1],
-                2 => foo(&[2]),
-                _ => &[3],
-            };
-        }
-
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T: ?Sized> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
-        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
-        "#,
+//- minicore: coerce_unsized
+fn foo<T>(x: &[T]) -> &[T] { loop {} }
+fn test(i: i32) {
+    let x = match i {
+        1 => &[1],
+        2 => foo(&[2]),
+        _ => &[3],
+    };
+}
+"#,
         expect![[r#"
             10..11 'x': &[T]
             27..38 '{ loop {} }': &[T]
@@ -470,15 +426,15 @@ fn coerce_autoderef() {
 #[test]
 fn coerce_autoderef_generic() {
     check_infer_with_mismatches(
-        r"
-        struct Foo;
-        fn takes_ref<T>(x: &T) -> T { *x }
-        fn test() {
-            takes_ref(&Foo);
-            takes_ref(&&Foo);
-            takes_ref(&&&Foo);
-        }
-        ",
+        r#"
+struct Foo;
+fn takes_ref<T>(x: &T) -> T { *x }
+fn test() {
+    takes_ref(&Foo);
+    takes_ref(&&Foo);
+    takes_ref(&&&Foo);
+}
+"#,
         expect![[r"
             28..29 'x': &T
             40..46 '{ *x }': T
@@ -508,30 +464,29 @@ fn coerce_autoderef_generic() {
 fn coerce_autoderef_block() {
     check_infer_with_mismatches(
         r#"
-        struct String {}
-        #[lang = "deref"]
-        trait Deref { type Target; }
-        impl Deref for String { type Target = str; }
-        fn takes_ref_str(x: &str) {}
-        fn returns_string() -> String { loop {} }
-        fn test() {
-            takes_ref_str(&{ returns_string() });
-        }
-        "#,
-        expect![[r"
-            126..127 'x': &str
-            135..137 '{}': ()
-            168..179 '{ loop {} }': String
-            170..177 'loop {}': !
-            175..177 '{}': ()
-            190..235 '{     ... }); }': ()
-            196..209 'takes_ref_str': fn takes_ref_str(&str)
-            196..232 'takes_...g() })': ()
-            210..231 '&{ ret...ng() }': &String
-            211..231 '{ retu...ng() }': String
-            213..227 'returns_string': fn returns_string() -> String
-            213..229 'return...ring()': String
-        "]],
+//- minicore: deref
+struct String {}
+impl core::ops::Deref for String { type Target = str; }
+fn takes_ref_str(x: &str) {}
+fn returns_string() -> String { loop {} }
+fn test() {
+    takes_ref_str(&{ returns_string() });
+}
+"#,
+        expect![[r#"
+            90..91 'x': &str
+            99..101 '{}': ()
+            132..143 '{ loop {} }': String
+            134..141 'loop {}': !
+            139..141 '{}': ()
+            154..199 '{     ... }); }': ()
+            160..173 'takes_ref_str': fn takes_ref_str(&str)
+            160..196 'takes_...g() })': ()
+            174..195 '&{ ret...ng() }': &String
+            175..195 '{ retu...ng() }': String
+            177..191 'returns_string': fn returns_string() -> String
+            177..193 'return...ring()': String
+        "#]],
     );
 }
 
@@ -674,25 +629,19 @@ fn coerce_placeholder_ref() {
 fn coerce_unsize_array() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "unsize"]
-        pub trait Unsize<T> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
-
-        fn test() {
-            let f: &[usize] = &[1, 2, 3];
-        }
+//- minicore: coerce_unsized
+fn test() {
+    let f: &[usize] = &[1, 2, 3];
+}
         "#,
         expect![[r#"
-            161..198 '{     ... 3]; }': ()
-            171..172 'f': &[usize]
-            185..195 '&[1, 2, 3]': &[usize; 3]
-            186..195 '[1, 2, 3]': [usize; 3]
-            187..188 '1': usize
-            190..191 '2': usize
-            193..194 '3': usize
+            10..47 '{     ... 3]; }': ()
+            20..21 'f': &[usize]
+            34..44 '&[1, 2, 3]': &[usize; 3]
+            35..44 '[1, 2, 3]': [usize; 3]
+            36..37 '1': usize
+            39..40 '2': usize
+            42..43 '3': usize
         "#]],
     );
 }
@@ -701,42 +650,34 @@ fn coerce_unsize_array() {
 fn coerce_unsize_trait_object_simple() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
-
-        trait Foo<T, U> {}
-        trait Bar<U, T, X>: Foo<T, U> {}
-        trait Baz<T, X>: Bar<usize, T, X> {}
-
-        struct S<T, X>;
-        impl<T, X> Foo<T, usize> for S<T, X> {}
-        impl<T, X> Bar<usize, T, X> for S<T, X> {}
-        impl<T, X> Baz<T, X> for S<T, X> {}
-
-        fn test() {
-            let obj: &dyn Baz<i8, i16> = &S;
-            let obj: &dyn Bar<_, i8, i16> = &S;
-            let obj: &dyn Foo<i8, _> = &S;
-        }
-        "#,
-        expect![[r"
-            424..539 '{     ... &S; }': ()
-            434..437 'obj': &dyn Baz<i8, i16>
-            459..461 '&S': &S<i8, i16>
-            460..461 'S': S<i8, i16>
-            471..474 'obj': &dyn Bar<usize, i8, i16>
-            499..501 '&S': &S<i8, i16>
-            500..501 'S': S<i8, i16>
-            511..514 'obj': &dyn Foo<i8, usize>
-            534..536 '&S': &S<i8, {unknown}>
-            535..536 'S': S<i8, {unknown}>
-        "]],
+//- minicore: coerce_unsized
+trait Foo<T, U> {}
+trait Bar<U, T, X>: Foo<T, U> {}
+trait Baz<T, X>: Bar<usize, T, X> {}
+
+struct S<T, X>;
+impl<T, X> Foo<T, usize> for S<T, X> {}
+impl<T, X> Bar<usize, T, X> for S<T, X> {}
+impl<T, X> Baz<T, X> for S<T, X> {}
+
+fn test() {
+    let obj: &dyn Baz<i8, i16> = &S;
+    let obj: &dyn Bar<_, i8, i16> = &S;
+    let obj: &dyn Foo<i8, _> = &S;
+}
+"#,
+        expect![[r#"
+            236..351 '{     ... &S; }': ()
+            246..249 'obj': &dyn Baz<i8, i16>
+            271..273 '&S': &S<i8, i16>
+            272..273 'S': S<i8, i16>
+            283..286 'obj': &dyn Bar<usize, i8, i16>
+            311..313 '&S': &S<i8, i16>
+            312..313 'S': S<i8, i16>
+            323..326 'obj': &dyn Foo<i8, usize>
+            346..348 '&S': &S<i8, {unknown}>
+            347..348 'S': S<i8, {unknown}>
+        "#]],
     );
 }
 
@@ -761,49 +702,41 @@ fn coerce_unsize_trait_object_to_trait_object() {
     //     602..606 'obj2': &dyn Baz<i8, i16>
     check_infer_with_mismatches(
         r#"
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
-
-        trait Foo<T, U> {}
-        trait Bar<U, T, X>: Foo<T, U> {}
-        trait Baz<T, X>: Bar<usize, T, X> {}
-
-        struct S<T, X>;
-        impl<T, X> Foo<T, usize> for S<T, X> {}
-        impl<T, X> Bar<usize, T, X> for S<T, X> {}
-        impl<T, X> Baz<T, X> for S<T, X> {}
-
-        fn test() {
-            let obj: &dyn Baz<i8, i16> = &S;
-            let obj: &dyn Bar<_, _, _> = obj;
-            let obj: &dyn Foo<_, _> = obj;
-            let obj2: &dyn Baz<i8, i16> = &S;
-            let _: &dyn Foo<_, _> = obj2;
-        }
-        "#,
+//- minicore: coerce_unsized
+trait Foo<T, U> {}
+trait Bar<U, T, X>: Foo<T, U> {}
+trait Baz<T, X>: Bar<usize, T, X> {}
+
+struct S<T, X>;
+impl<T, X> Foo<T, usize> for S<T, X> {}
+impl<T, X> Bar<usize, T, X> for S<T, X> {}
+impl<T, X> Baz<T, X> for S<T, X> {}
+
+fn test() {
+    let obj: &dyn Baz<i8, i16> = &S;
+    let obj: &dyn Bar<_, _, _> = obj;
+    let obj: &dyn Foo<_, _> = obj;
+    let obj2: &dyn Baz<i8, i16> = &S;
+    let _: &dyn Foo<_, _> = obj2;
+}
+"#,
         expect![[r#"
-            424..609 '{     ...bj2; }': ()
-            434..437 'obj': &dyn Baz<i8, i16>
-            459..461 '&S': &S<i8, i16>
-            460..461 'S': S<i8, i16>
-            471..474 'obj': &dyn Bar<{unknown}, {unknown}, {unknown}>
-            496..499 'obj': &dyn Baz<i8, i16>
-            509..512 'obj': &dyn Foo<{unknown}, {unknown}>
-            531..534 'obj': &dyn Bar<{unknown}, {unknown}, {unknown}>
-            544..548 'obj2': &dyn Baz<i8, i16>
-            570..572 '&S': &S<i8, i16>
-            571..572 'S': S<i8, i16>
-            582..583 '_': &dyn Foo<{unknown}, {unknown}>
-            602..606 'obj2': &dyn Baz<i8, i16>
-            496..499: expected &dyn Bar<{unknown}, {unknown}, {unknown}>, got &dyn Baz<i8, i16>
-            531..534: expected &dyn Foo<{unknown}, {unknown}>, got &dyn Bar<{unknown}, {unknown}, {unknown}>
-            602..606: expected &dyn Foo<{unknown}, {unknown}>, got &dyn Baz<i8, i16>
+            236..421 '{     ...bj2; }': ()
+            246..249 'obj': &dyn Baz<i8, i16>
+            271..273 '&S': &S<i8, i16>
+            272..273 'S': S<i8, i16>
+            283..286 'obj': &dyn Bar<{unknown}, {unknown}, {unknown}>
+            308..311 'obj': &dyn Baz<i8, i16>
+            321..324 'obj': &dyn Foo<{unknown}, {unknown}>
+            343..346 'obj': &dyn Bar<{unknown}, {unknown}, {unknown}>
+            356..360 'obj2': &dyn Baz<i8, i16>
+            382..384 '&S': &S<i8, i16>
+            383..384 'S': S<i8, i16>
+            394..395 '_': &dyn Foo<{unknown}, {unknown}>
+            414..418 'obj2': &dyn Baz<i8, i16>
+            308..311: expected &dyn Bar<{unknown}, {unknown}, {unknown}>, got &dyn Baz<i8, i16>
+            343..346: expected &dyn Foo<{unknown}, {unknown}>, got &dyn Bar<{unknown}, {unknown}, {unknown}>
+            414..418: expected &dyn Foo<{unknown}, {unknown}>, got &dyn Baz<i8, i16>
         "#]],
     );
 }
@@ -812,40 +745,32 @@ fn coerce_unsize_trait_object_to_trait_object() {
 fn coerce_unsize_super_trait_cycle() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "sized"]
-        pub trait Sized {}
-        #[lang = "unsize"]
-        pub trait Unsize<T> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
-
-        trait A {}
-        trait B: C + A {}
-        trait C: B {}
-        trait D: C
-
-        struct S;
-        impl A for S {}
-        impl B for S {}
-        impl C for S {}
-        impl D for S {}
-
-        fn test() {
-            let obj: &dyn D = &S;
-            let obj: &dyn A = &S;
-        }
-        "#,
-        expect![[r"
-            328..383 '{     ... &S; }': ()
-            338..341 'obj': &dyn D
-            352..354 '&S': &S
-            353..354 'S': S
-            364..367 'obj': &dyn A
-            378..380 '&S': &S
-            379..380 'S': S
-        "]],
+//- minicore: coerce_unsized
+trait A {}
+trait B: C + A {}
+trait C: B {}
+trait D: C
+
+struct S;
+impl A for S {}
+impl B for S {}
+impl C for S {}
+impl D for S {}
+
+fn test() {
+    let obj: &dyn D = &S;
+    let obj: &dyn A = &S;
+}
+"#,
+        expect![[r#"
+            140..195 '{     ... &S; }': ()
+            150..153 'obj': &dyn D
+            164..166 '&S': &S
+            165..166 'S': S
+            176..179 'obj': &dyn A
+            190..192 '&S': &S
+            191..192 'S': S
+        "#]],
     );
 }
 
@@ -854,41 +779,35 @@ fn coerce_unsize_generic() {
     // FIXME: fix the type mismatches here
     check_infer_with_mismatches(
         r#"
-        #[lang = "unsize"]
-        pub trait Unsize<T> {}
-        #[lang = "coerce_unsized"]
-        pub trait CoerceUnsized<T> {}
-
-        impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
+//- minicore: coerce_unsized
+struct Foo<T> { t: T };
+struct Bar<T>(Foo<T>);
 
-        struct Foo<T> { t: T };
-        struct Bar<T>(Foo<T>);
-
-        fn test() {
-            let _: &Foo<[usize]> = &Foo { t: [1, 2, 3] };
-            let _: &Bar<[usize]> = &Bar(Foo { t: [1, 2, 3] });
-        }
-        "#,
+fn test() {
+    let _: &Foo<[usize]> = &Foo { t: [1, 2, 3] };
+    let _: &Bar<[usize]> = &Bar(Foo { t: [1, 2, 3] });
+}
+"#,
         expect![[r#"
-            209..317 '{     ... }); }': ()
-            219..220 '_': &Foo<[usize]>
-            238..259 '&Foo {..., 3] }': &Foo<[usize]>
-            239..259 'Foo { ..., 3] }': Foo<[usize]>
-            248..257 '[1, 2, 3]': [usize; 3]
-            249..250 '1': usize
-            252..253 '2': usize
-            255..256 '3': usize
-            269..270 '_': &Bar<[usize]>
-            288..314 '&Bar(F... 3] })': &Bar<[i32; 3]>
-            289..292 'Bar': Bar<[i32; 3]>(Foo<[i32; 3]>) -> Bar<[i32; 3]>
-            289..314 'Bar(Fo... 3] })': Bar<[i32; 3]>
-            293..313 'Foo { ..., 3] }': Foo<[i32; 3]>
-            302..311 '[1, 2, 3]': [i32; 3]
-            303..304 '1': i32
-            306..307 '2': i32
-            309..310 '3': i32
-            248..257: expected [usize], got [usize; 3]
-            288..314: expected &Bar<[usize]>, got &Bar<[i32; 3]>
+            58..166 '{     ... }); }': ()
+            68..69 '_': &Foo<[usize]>
+            87..108 '&Foo {..., 3] }': &Foo<[usize]>
+            88..108 'Foo { ..., 3] }': Foo<[usize]>
+            97..106 '[1, 2, 3]': [usize; 3]
+            98..99 '1': usize
+            101..102 '2': usize
+            104..105 '3': usize
+            118..119 '_': &Bar<[usize]>
+            137..163 '&Bar(F... 3] })': &Bar<[i32; 3]>
+            138..141 'Bar': Bar<[i32; 3]>(Foo<[i32; 3]>) -> Bar<[i32; 3]>
+            138..163 'Bar(Fo... 3] })': Bar<[i32; 3]>
+            142..162 'Foo { ..., 3] }': Foo<[i32; 3]>
+            151..160 '[1, 2, 3]': [i32; 3]
+            152..153 '1': i32
+            155..156 '2': i32
+            158..159 '3': i32
+            97..106: expected [usize], got [usize; 3]
+            137..163: expected &Bar<[usize]>, got &Bar<[i32; 3]>
         "#]],
     );
 }
@@ -898,15 +817,7 @@ fn coerce_unsize_apit() {
     // FIXME: #8984
     check_infer_with_mismatches(
         r#"
-#[lang = "sized"]
-pub trait Sized {}
-#[lang = "unsize"]
-pub trait Unsize<T> {}
-#[lang = "coerce_unsized"]
-pub trait CoerceUnsized<T> {}
-
-impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
-
+//- minicore: coerce_unsized
 trait Foo {}
 
 fn test(f: impl Foo) {
@@ -914,12 +825,12 @@ fn test(f: impl Foo) {
 }
         "#,
         expect![[r#"
-            210..211 'f': impl Foo
-            223..252 '{     ... &f; }': ()
-            233..234 '_': &dyn Foo
-            247..249 '&f': &impl Foo
-            248..249 'f': impl Foo
-            247..249: expected &dyn Foo, got &impl Foo
+            22..23 'f': impl Foo
+            35..64 '{     ... &f; }': ()
+            45..46 '_': &dyn Foo
+            59..61 '&f': &impl Foo
+            60..61 'f': impl Foo
+            59..61: expected &dyn Foo, got &impl Foo
         "#]],
     );
 }
@@ -1015,15 +926,7 @@ fn main() {
 fn coerce_unsize_expected_type() {
     check_no_mismatches(
         r#"
-#[lang = "sized"]
-pub trait Sized {}
-#[lang = "unsize"]
-pub trait Unsize<T> {}
-#[lang = "coerce_unsized"]
-pub trait CoerceUnsized<T> {}
-
-impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
-
+//- minicore: coerce_unsized
 fn main() {
     let foo: &[u32] = &[1, 2];
     let foo: &[u32] = match true {
diff --git a/crates/hir_ty/src/tests/method_resolution.rs b/crates/hir_ty/src/tests/method_resolution.rs
index f26b2c8a7..d9b5ee9cf 100644
--- a/crates/hir_ty/src/tests/method_resolution.rs
+++ b/crates/hir_ty/src/tests/method_resolution.rs
@@ -780,10 +780,7 @@ fn test() { (&S).foo(); }
 fn method_resolution_unsize_array() {
     check_types(
         r#"
-#[lang = "slice"]
-impl<T> [T] {
-    fn len(&self) -> usize { loop {} }
-}
+//- minicore: slice
 fn test() {
     let a = [1, 2, 3];
     a.len();
@@ -1178,11 +1175,7 @@ fn main() {
 fn autoderef_visibility_field() {
     check_infer(
         r#"
-#[lang = "deref"]
-pub trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
+//- minicore: deref
 mod a {
     pub struct Foo(pub char);
     pub struct Bar(i32);
@@ -1191,7 +1184,7 @@ mod a {
             Self(0)
         }
     }
-    impl super::Deref for Bar {
+    impl core::ops::Deref for Bar {
         type Target = Foo;
         fn deref(&self) -> &Foo {
             &Foo('z')
@@ -1205,22 +1198,21 @@ mod b {
 }
         "#,
         expect![[r#"
-            67..71 'self': &Self
-            200..231 '{     ...     }': Bar
-            214..218 'Self': Bar(i32) -> Bar
-            214..221 'Self(0)': Bar
-            219..220 '0': i32
-            315..319 'self': &Bar
-            329..362 '{     ...     }': &Foo
-            343..352 '&Foo('z')': &Foo
-            344..347 'Foo': Foo(char) -> Foo
-            344..352 'Foo('z')': Foo
-            348..351 ''z'': char
-            392..439 '{     ...     }': ()
-            406..407 'x': char
-            410..428 'super:...r::new': fn new() -> Bar
-            410..430 'super:...:new()': Bar
-            410..432 'super:...ew().0': char
+            107..138 '{     ...     }': Bar
+            121..125 'Self': Bar(i32) -> Bar
+            121..128 'Self(0)': Bar
+            126..127 '0': i32
+            226..230 'self': &Bar
+            240..273 '{     ...     }': &Foo
+            254..263 '&Foo('z')': &Foo
+            255..258 'Foo': Foo(char) -> Foo
+            255..263 'Foo('z')': Foo
+            259..262 ''z'': char
+            303..350 '{     ...     }': ()
+            317..318 'x': char
+            321..339 'super:...r::new': fn new() -> Bar
+            321..341 'super:...:new()': Bar
+            321..343 'super:...ew().0': char
         "#]],
     )
 }
@@ -1230,11 +1222,7 @@ fn autoderef_visibility_method() {
     cov_mark::check!(autoderef_candidate_not_visible);
     check_infer(
         r#"
-#[lang = "deref"]
-pub trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
+//- minicore: deref
 mod a {
     pub struct Foo(pub char);
     impl Foo {
@@ -1251,7 +1239,7 @@ mod a {
             self.0
         }
     }
-    impl super::Deref for Bar {
+    impl core::ops::Deref for Bar {
         type Target = Foo;
         fn deref(&self) -> &Foo {
             &Foo('z')
@@ -1265,30 +1253,29 @@ mod b {
 }
         "#,
         expect![[r#"
-            67..71 'self': &Self
-            168..172 'self': &Foo
-            182..212 '{     ...     }': char
-            196..200 'self': &Foo
-            196..202 'self.0': char
-            288..319 '{     ...     }': Bar
-            302..306 'Self': Bar(i32) -> Bar
-            302..309 'Self(0)': Bar
-            307..308 '0': i32
-            338..342 'self': &Bar
-            351..381 '{     ...     }': i32
-            365..369 'self': &Bar
-            365..371 'self.0': i32
-            465..469 'self': &Bar
-            479..512 '{     ...     }': &Foo
-            493..502 '&Foo('z')': &Foo
-            494..497 'Foo': Foo(char) -> Foo
-            494..502 'Foo('z')': Foo
-            498..501 ''z'': char
-            542..595 '{     ...     }': ()
-            556..557 'x': char
-            560..578 'super:...r::new': fn new() -> Bar
-            560..580 'super:...:new()': Bar
-            560..588 'super:...ango()': char
+            75..79 'self': &Foo
+            89..119 '{     ...     }': char
+            103..107 'self': &Foo
+            103..109 'self.0': char
+            195..226 '{     ...     }': Bar
+            209..213 'Self': Bar(i32) -> Bar
+            209..216 'Self(0)': Bar
+            214..215 '0': i32
+            245..249 'self': &Bar
+            258..288 '{     ...     }': i32
+            272..276 'self': &Bar
+            272..278 'self.0': i32
+            376..380 'self': &Bar
+            390..423 '{     ...     }': &Foo
+            404..413 '&Foo('z')': &Foo
+            405..408 'Foo': Foo(char) -> Foo
+            405..413 'Foo('z')': Foo
+            409..412 ''z'': char
+            453..506 '{     ...     }': ()
+            467..468 'x': char
+            471..489 'super:...r::new': fn new() -> Bar
+            471..491 'super:...:new()': Bar
+            471..499 'super:...ango()': char
         "#]],
     )
 }
diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index 1019e783b..abd9c385a 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -927,35 +927,33 @@ fn issue_6628() {
 fn issue_6852() {
     check_infer(
         r#"
-        #[lang = "deref"]
-        pub trait Deref {
-            type Target;
-        }
+//- minicore: deref
+use core::ops::Deref;
 
-        struct BufWriter {}
+struct BufWriter {}
 
-        struct Mutex<T> {}
-        struct MutexGuard<'a, T> {}
-        impl<T> Mutex<T> {
-            fn lock(&self) -> MutexGuard<'_, T> {}
-        }
-        impl<'a, T: 'a> Deref for MutexGuard<'a, T> {
-            type Target = T;
-        }
-        fn flush(&self) {
-            let w: &Mutex<BufWriter>;
-            *(w.lock());
-        }
-        "#,
+struct Mutex<T> {}
+struct MutexGuard<'a, T> {}
+impl<T> Mutex<T> {
+    fn lock(&self) -> MutexGuard<'_, T> {}
+}
+impl<'a, T: 'a> Deref for MutexGuard<'a, T> {
+    type Target = T;
+}
+fn flush(&self) {
+    let w: &Mutex<BufWriter>;
+    *(w.lock());
+}
+"#,
         expect![[r#"
-            156..160 'self': &Mutex<T>
-            183..185 '{}': ()
-            267..271 'self': &{unknown}
-            273..323 '{     ...()); }': ()
-            283..284 'w': &Mutex<BufWriter>
-            309..320 '*(w.lock())': BufWriter
-            311..312 'w': &Mutex<BufWriter>
-            311..319 'w.lock()': MutexGuard<BufWriter>
+            123..127 'self': &Mutex<T>
+            150..152 '{}': ()
+            234..238 'self': &{unknown}
+            240..290 '{     ...()); }': ()
+            250..251 'w': &Mutex<BufWriter>
+            276..287 '*(w.lock())': BufWriter
+            278..279 'w': &Mutex<BufWriter>
+            278..286 'w.lock()': MutexGuard<BufWriter>
         "#]],
     );
 }
@@ -977,37 +975,33 @@ fn param_overrides_fn() {
 fn lifetime_from_chalk_during_deref() {
     check_types(
         r#"
-        #[lang = "deref"]
-        pub trait Deref {
-            type Target;
-        }
-
-        struct Box<T: ?Sized> {}
-        impl<T> Deref for Box<T> {
-            type Target = T;
+//- minicore: deref
+struct Box<T: ?Sized> {}
+impl<T> core::ops::Deref for Box<T> {
+    type Target = T;
 
-            fn deref(&self) -> &Self::Target {
-                loop {}
-            }
-        }
+    fn deref(&self) -> &Self::Target {
+        loop {}
+    }
+}
 
-        trait Iterator {
-            type Item;
-        }
+trait Iterator {
+    type Item;
+}
 
-        pub struct Iter<'a, T: 'a> {
-            inner: Box<dyn IterTrait<'a, T, Item = &'a T> + 'a>,
-        }
+pub struct Iter<'a, T: 'a> {
+    inner: Box<dyn IterTrait<'a, T, Item = &'a T> + 'a>,
+}
 
-        trait IterTrait<'a, T: 'a>: Iterator<Item = &'a T> {
-            fn clone_box(&self);
-        }
+trait IterTrait<'a, T: 'a>: Iterator<Item = &'a T> {
+    fn clone_box(&self);
+}
 
-        fn clone_iter<T>(s: Iter<T>) {
-            s.inner.clone_box();
-          //^^^^^^^^^^^^^^^^^^^ ()
-        }
-        "#,
+fn clone_iter<T>(s: Iter<T>) {
+    s.inner.clone_box();
+    //^^^^^^^^^^^^^^^^^^^ ()
+}
+"#,
     )
 }
 
diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index 3418ed21e..68776f3c0 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -113,7 +113,7 @@ fn type_alias_in_struct_lit() {
 fn infer_ranges() {
     check_types(
         r#"
-//- /main.rs crate:main deps:core
+//- minicore: range
 fn test() {
     let a = ..;
     let b = 1..;
@@ -125,32 +125,6 @@ fn test() {
     let t = (a, b, c, d, e, f);
     t;
 } //^ (RangeFull, RangeFrom<i32>, RangeTo<u32>, Range<usize>, RangeToInclusive<i32>, RangeInclusive<char>)
-
-//- /core.rs crate:core
-#[prelude_import] use prelude::*;
-mod prelude {}
-
-pub mod ops {
-    pub struct Range<Idx> {
-        pub start: Idx,
-        pub end: Idx,
-    }
-    pub struct RangeFrom<Idx> {
-        pub start: Idx,
-    }
-    struct RangeFull;
-    pub struct RangeInclusive<Idx> {
-        start: Idx,
-        end: Idx,
-        is_empty: u8,
-    }
-    pub struct RangeTo<Idx> {
-        pub end: Idx,
-    }
-    pub struct RangeToInclusive<Idx> {
-        pub end: Idx,
-    }
-}
 "#,
     );
 }
@@ -175,16 +149,17 @@ fn test() {
 fn infer_basics() {
     check_infer(
         r#"
-        fn test(a: u32, b: isize, c: !, d: &str) {
-            a;
-            b;
-            c;
-            d;
-            1usize;
-            1isize;
-            "test";
-            1.0f32;
-        }"#,
+fn test(a: u32, b: isize, c: !, d: &str) {
+    a;
+    b;
+    c;
+    d;
+    1usize;
+    1isize;
+    "test";
+    1.0f32;
+}
+"#,
         expect![[r#"
             8..9 'a': u32
             16..17 'b': isize
@@ -207,15 +182,15 @@ fn infer_basics() {
 fn infer_let() {
     check_infer(
         r#"
-        fn test() {
-            let a = 1isize;
-            let b: usize = 1;
-            let c = b;
-            let d: u32;
-            let e;
-            let f: i32 = e;
-        }
-        "#,
+fn test() {
+    let a = 1isize;
+    let b: usize = 1;
+    let c = b;
+    let d: u32;
+    let e;
+    let f: i32 = e;
+}
+"#,
         expect![[r#"
             10..117 '{     ...= e; }': ()
             20..21 'a': isize
@@ -236,17 +211,17 @@ fn infer_let() {
 fn infer_paths() {
     check_infer(
         r#"
-        fn a() -> u32 { 1 }
+fn a() -> u32 { 1 }
 
-        mod b {
-            fn c() -> u32 { 1 }
-        }
+mod b {
+    fn c() -> u32 { 1 }
+}
 
-        fn test() {
-            a();
-            b::c();
-        }
-        "#,
+fn test() {
+    a();
+    b::c();
+}
+"#,
         expect![[r#"
             14..19 '{ 1 }': u32
             16..17 '1': u32
@@ -265,17 +240,17 @@ fn infer_paths() {
 fn infer_path_type() {
     check_infer(
         r#"
-        struct S;
+struct S;
 
-        impl S {
-            fn foo() -> i32 { 1 }
-        }
+impl S {
+    fn foo() -> i32 { 1 }
+}
 
-        fn test() {
-            S::foo();
-            <S>::foo();
-        }
-        "#,
+fn test() {
+    S::foo();
+    <S>::foo();
+}
+"#,
         expect![[r#"
             40..45 '{ 1 }': i32
             42..43 '1': i32
@@ -292,21 +267,21 @@ fn infer_path_type() {
 fn infer_struct() {
     check_infer(
         r#"
-        struct A {
-            b: B,
-            c: C,
-        }
-        struct B;
-        struct C(usize);
+struct A {
+    b: B,
+    c: C,
+}
+struct B;
+struct C(usize);
 
-        fn test() {
-            let c = C(1);
-            B;
-            let a: A = A { b: B, c: C(1) };
-            a.b;
-            a.c;
-        }
-        "#,
+fn test() {
+    let c = C(1);
+    B;
+    let a: A = A { b: B, c: C(1) };
+    a.b;
+    a.c;
+}
+"#,
         expect![[r#"
             71..153 '{     ...a.c; }': ()
             81..82 'c': C
@@ -332,14 +307,15 @@ fn infer_struct() {
 fn infer_enum() {
     check_infer(
         r#"
-        enum E {
-            V1 { field: u32 },
-            V2
-        }
-        fn test() {
-            E::V1 { field: 1 };
-            E::V2;
-        }"#,
+enum E {
+    V1 { field: u32 },
+    V2
+}
+fn test() {
+    E::V1 { field: 1 };
+    E::V2;
+}
+"#,
         expect![[r#"
             51..89 '{     ...:V2; }': ()
             57..75 'E::V1 ...d: 1 }': E
@@ -353,23 +329,23 @@ fn infer_enum() {
 fn infer_union() {
     check_infer(
         r#"
-        union MyUnion {
-            foo: u32,
-            bar: f32,
-        }
+union MyUnion {
+    foo: u32,
+    bar: f32,
+}
 
-        fn test() {
-            let u = MyUnion { foo: 0 };
-            unsafe { baz(u); }
-            let u = MyUnion { bar: 0.0 };
-            unsafe { baz(u); }
-        }
+fn test() {
+    let u = MyUnion { foo: 0 };
+    unsafe { baz(u); }
+    let u = MyUnion { bar: 0.0 };
+    unsafe { baz(u); }
+}
 
-        unsafe fn baz(u: MyUnion) {
-            let inner = u.foo;
-            let inner = u.bar;
-        }
-        "#,
+unsafe fn baz(u: MyUnion) {
+    let inner = u.foo;
+    let inner = u.bar;
+}
+"#,
         expect![[r#"
             57..172 '{     ...); } }': ()
             67..68 'u': MyUnion
@@ -404,19 +380,19 @@ fn infer_union() {
 fn infer_refs() {
     check_infer(
         r#"
-        fn test(a: &u32, b: &mut u32, c: *const u32, d: *mut u32) {
-            a;
-            *a;
-            &a;
-            &mut a;
-            b;
-            *b;
-            &b;
-            c;
-            *c;
-            d;
-            *d;
-        }
+fn test(a: &u32, b: &mut u32, c: *const u32, d: *mut u32) {
+    a;
+    *a;
+    &a;
+    &mut a;
+    b;
+    *b;
+    &b;
+    c;
+    *c;
+    d;
+    *d;
+}
         "#,
         expect![[r#"
             8..9 'a': &u32
@@ -450,11 +426,11 @@ fn infer_refs() {
 fn infer_raw_ref() {
     check_infer(
         r#"
-        fn test(a: i32) {
-            &raw mut a;
-            &raw const a;
-        }
-        "#,
+fn test(a: i32) {
+    &raw mut a;
+    &raw const a;
+}
+"#,
         expect![[r#"
             8..9 'a': i32
             16..53 '{     ...t a; }': ()
@@ -524,26 +500,26 @@ h";
 fn infer_unary_op() {
     check_infer(
         r#"
-        enum SomeType {}
-
-        fn test(x: SomeType) {
-            let b = false;
-            let c = !b;
-            let a = 100;
-            let d: i128 = -a;
-            let e = -100;
-            let f = !!!true;
-            let g = !42;
-            let h = !10u32;
-            let j = !a;
-            -3.14;
-            !3;
-            -x;
-            !x;
-            -"hello";
-            !"hello";
-        }
-        "#,
+enum SomeType {}
+
+fn test(x: SomeType) {
+    let b = false;
+    let c = !b;
+    let a = 100;
+    let d: i128 = -a;
+    let e = -100;
+    let f = !!!true;
+    let g = !42;
+    let h = !10u32;
+    let j = !a;
+    -3.14;
+    !3;
+    -x;
+    !x;
+    -"hello";
+    !"hello";
+}
+"#,
         expect![[r#"
             26..27 'x': SomeType
             39..271 '{     ...lo"; }': ()
@@ -594,19 +570,19 @@ fn infer_unary_op() {
 fn infer_backwards() {
     check_infer(
         r#"
-        fn takes_u32(x: u32) {}
+fn takes_u32(x: u32) {}
 
-        struct S { i32_field: i32 }
+struct S { i32_field: i32 }
 
-        fn test() -> &mut &f64 {
-            let a = unknown_function();
-            takes_u32(a);
-            let b = unknown_function();
-            S { i32_field: b };
-            let c = unknown_function();
-            &mut &c
-        }
-        "#,
+fn test() -> &mut &f64 {
+    let a = unknown_function();
+    takes_u32(a);
+    let b = unknown_function();
+    S { i32_field: b };
+    let c = unknown_function();
+    &mut &c
+}
+"#,
         expect![[r#"
             13..14 'x': u32
             21..23 '{}': ()
@@ -636,23 +612,23 @@ fn infer_backwards() {
 fn infer_self() {
     check_infer(
         r#"
-        struct S;
+struct S;
 
-        impl S {
-            fn test(&self) {
-                self;
-            }
-            fn test2(self: &Self) {
-                self;
-            }
-            fn test3() -> Self {
-                S {}
-            }
-            fn test4() -> Self {
-                Self {}
-            }
-        }
-        "#,
+impl S {
+    fn test(&self) {
+        self;
+    }
+    fn test2(self: &Self) {
+        self;
+    }
+    fn test3() -> Self {
+        S {}
+    }
+    fn test4() -> Self {
+        Self {}
+    }
+}
+"#,
         expect![[r#"
             33..37 'self': &S
             39..60 '{     ...     }': ()
@@ -672,30 +648,30 @@ fn infer_self() {
 fn infer_self_as_path() {
     check_infer(
         r#"
-        struct S1;
-        struct S2(isize);
-        enum E {
-            V1,
-            V2(u32),
-        }
+struct S1;
+struct S2(isize);
+enum E {
+    V1,
+    V2(u32),
+}
 
-        impl S1 {
-            fn test() {
-                Self;
-            }
-        }
-        impl S2 {
-            fn test() {
-                Self(1);
-            }
-        }
-        impl E {
-            fn test() {
-                Self::V1;
-                Self::V2(1);
-            }
-        }
-        "#,
+impl S1 {
+    fn test() {
+        Self;
+    }
+}
+impl S2 {
+    fn test() {
+        Self(1);
+    }
+}
+impl E {
+    fn test() {
+        Self::V1;
+        Self::V2(1);
+    }
+}
+"#,
         expect![[r#"
             86..107 '{     ...     }': ()
             96..100 'Self': S1
@@ -716,26 +692,26 @@ fn infer_self_as_path() {
 fn infer_binary_op() {
     check_infer(
         r#"
-        fn f(x: bool) -> i32 {
-            0i32
-        }
+fn f(x: bool) -> i32 {
+    0i32
+}
 
-        fn test() -> bool {
-            let x = a && b;
-            let y = true || false;
-            let z = x == y;
-            let t = x != y;
-            let minus_forty: isize = -40isize;
-            let h = minus_forty <= CONST_2;
-            let c = f(z || y) + 5;
-            let d = b;
-            let g = minus_forty ^= i;
-            let ten: usize = 10;
-            let ten_is_eleven = ten == some_num;
-
-            ten < 3
-        }
-        "#,
+fn test() -> bool {
+    let x = a && b;
+    let y = true || false;
+    let z = x == y;
+    let t = x != y;
+    let minus_forty: isize = -40isize;
+    let h = minus_forty <= CONST_2;
+    let c = f(z || y) + 5;
+    let d = b;
+    let g = minus_forty ^= i;
+    let ten: usize = 10;
+    let ten_is_eleven = ten == some_num;
+
+    ten < 3
+}
+"#,
         expect![[r#"
             5..6 'x': bool
             21..33 '{     0i32 }': i32
@@ -795,11 +771,11 @@ fn infer_binary_op() {
 fn infer_shift_op() {
     check_infer(
         r#"
-        fn test() {
-            1u32 << 5u8;
-            1u32 >> 5u8;
-        }
-        "#,
+fn test() {
+    1u32 << 5u8;
+    1u32 >> 5u8;
+}
+"#,
         expect![[r#"
             10..47 '{     ...5u8; }': ()
             16..20 '1u32': u32
@@ -816,29 +792,29 @@ fn infer_shift_op() {
 fn infer_field_autoderef() {
     check_infer(
         r#"
-        struct A {
-            b: B,
-        }
-        struct B;
-
-        fn test1(a: A) {
-            let a1 = a;
-            a1.b;
-            let a2 = &a;
-            a2.b;
-            let a3 = &mut a;
-            a3.b;
-            let a4 = &&&&&&&a;
-            a4.b;
-            let a5 = &mut &&mut &&mut a;
-            a5.b;
-        }
+struct A {
+    b: B,
+}
+struct B;
 
-        fn test2(a1: *const A, a2: *mut A) {
-            a1.b;
-            a2.b;
-        }
-        "#,
+fn test1(a: A) {
+    let a1 = a;
+    a1.b;
+    let a2 = &a;
+    a2.b;
+    let a3 = &mut a;
+    a3.b;
+    let a4 = &&&&&&&a;
+    a4.b;
+    let a5 = &mut &&mut &&mut a;
+    a5.b;
+}
+
+fn test2(a1: *const A, a2: *mut A) {
+    a1.b;
+    a2.b;
+}
+"#,
         expect![[r#"
             43..44 'a': A
             49..212 '{     ...5.b; }': ()
@@ -891,58 +867,53 @@ fn infer_field_autoderef() {
 fn infer_argument_autoderef() {
     check_infer(
         r#"
-        #[lang = "deref"]
-        pub trait Deref {
-            type Target;
-            fn deref(&self) -> &Self::Target;
-        }
-
-        struct A<T>(T);
+//- minicore: deref
+use core::ops::Deref;
+struct A<T>(T);
 
-        impl<T> A<T> {
-            fn foo(&self) -> &T {
-                &self.0
-            }
-        }
+impl<T> A<T> {
+    fn foo(&self) -> &T {
+        &self.0
+    }
+}
 
-        struct B<T>(T);
+struct B<T>(T);
 
-        impl<T> Deref for B<T> {
-            type Target = T;
-            fn deref(&self) -> &Self::Target {
-                &self.0
-            }
-        }
+impl<T> Deref for B<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
 
-        fn test() {
-            let t = A::foo(&&B(B(A(42))));
-        }
-        "#,
+fn test() {
+    let t = A::foo(&&B(B(A(42))));
+}
+"#,
         expect![[r#"
-            67..71 'self': &Self
-            138..142 'self': &A<T>
-            150..173 '{     ...     }': &T
-            160..167 '&self.0': &T
-            161..165 'self': &A<T>
-            161..167 'self.0': T
-            254..258 'self': &B<T>
-            277..300 '{     ...     }': &T
-            287..294 '&self.0': &T
-            288..292 'self': &B<T>
-            288..294 'self.0': T
-            314..352 '{     ...))); }': ()
-            324..325 't': &i32
-            328..334 'A::foo': fn foo<i32>(&A<i32>) -> &i32
-            328..349 'A::foo...42))))': &i32
-            335..348 '&&B(B(A(42)))': &&B<B<A<i32>>>
-            336..348 '&B(B(A(42)))': &B<B<A<i32>>>
-            337..338 'B': B<B<A<i32>>>(B<A<i32>>) -> B<B<A<i32>>>
-            337..348 'B(B(A(42)))': B<B<A<i32>>>
-            339..340 'B': B<A<i32>>(A<i32>) -> B<A<i32>>
-            339..347 'B(A(42))': B<A<i32>>
-            341..342 'A': A<i32>(i32) -> A<i32>
-            341..346 'A(42)': A<i32>
-            343..345 '42': i32
+            66..70 'self': &A<T>
+            78..101 '{     ...     }': &T
+            88..95 '&self.0': &T
+            89..93 'self': &A<T>
+            89..95 'self.0': T
+            182..186 'self': &B<T>
+            205..228 '{     ...     }': &T
+            215..222 '&self.0': &T
+            216..220 'self': &B<T>
+            216..222 'self.0': T
+            242..280 '{     ...))); }': ()
+            252..253 't': &i32
+            256..262 'A::foo': fn foo<i32>(&A<i32>) -> &i32
+            256..277 'A::foo...42))))': &i32
+            263..276 '&&B(B(A(42)))': &&B<B<A<i32>>>
+            264..276 '&B(B(A(42)))': &B<B<A<i32>>>
+            265..266 'B': B<B<A<i32>>>(B<A<i32>>) -> B<B<A<i32>>>
+            265..276 'B(B(A(42)))': B<B<A<i32>>>
+            267..268 'B': B<A<i32>>(A<i32>) -> B<A<i32>>
+            267..275 'B(A(42))': B<A<i32>>
+            269..270 'A': A<i32>(i32) -> A<i32>
+            269..274 'A(42)': A<i32>
+            271..273 '42': i32
         "#]],
     );
 }
@@ -951,62 +922,57 @@ fn infer_argument_autoderef() {
 fn infer_method_argument_autoderef() {
     check_infer(
         r#"
-        #[lang = "deref"]
-        pub trait Deref {
-            type Target;
-            fn deref(&self) -> &Self::Target;
-        }
+//- minicore: deref
+use core::ops::Deref;
+struct A<T>(*mut T);
 
-        struct A<T>(*mut T);
-
-        impl<T> A<T> {
-            fn foo(&self, x: &A<T>) -> &T {
-                &*x.0
-            }
-        }
+impl<T> A<T> {
+    fn foo(&self, x: &A<T>) -> &T {
+        &*x.0
+    }
+}
 
-        struct B<T>(T);
+struct B<T>(T);
 
-        impl<T> Deref for B<T> {
-            type Target = T;
-            fn deref(&self) -> &Self::Target {
-                &self.0
-            }
-        }
+impl<T> Deref for B<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
 
-        fn test(a: A<i32>) {
-            let t = A(0 as *mut _).foo(&&B(B(a)));
-        }
-        "#,
+fn test(a: A<i32>) {
+    let t = A(0 as *mut _).foo(&&B(B(a)));
+}
+"#,
         expect![[r#"
-            67..71 'self': &Self
-            143..147 'self': &A<T>
-            149..150 'x': &A<T>
-            165..186 '{     ...     }': &T
-            175..180 '&*x.0': &T
-            176..180 '*x.0': T
-            177..178 'x': &A<T>
-            177..180 'x.0': *mut T
-            267..271 'self': &B<T>
-            290..313 '{     ...     }': &T
-            300..307 '&self.0': &T
-            301..305 'self': &B<T>
-            301..307 'self.0': T
-            325..326 'a': A<i32>
-            336..382 '{     ...))); }': ()
-            346..347 't': &i32
-            350..351 'A': A<i32>(*mut i32) -> A<i32>
-            350..364 'A(0 as *mut _)': A<i32>
-            350..379 'A(0 as...B(a)))': &i32
-            352..353 '0': i32
-            352..363 '0 as *mut _': *mut i32
-            369..378 '&&B(B(a))': &&B<B<A<i32>>>
-            370..378 '&B(B(a))': &B<B<A<i32>>>
-            371..372 'B': B<B<A<i32>>>(B<A<i32>>) -> B<B<A<i32>>>
-            371..378 'B(B(a))': B<B<A<i32>>>
-            373..374 'B': B<A<i32>>(A<i32>) -> B<A<i32>>
-            373..377 'B(a)': B<A<i32>>
-            375..376 'a': A<i32>
+            71..75 'self': &A<T>
+            77..78 'x': &A<T>
+            93..114 '{     ...     }': &T
+            103..108 '&*x.0': &T
+            104..108 '*x.0': T
+            105..106 'x': &A<T>
+            105..108 'x.0': *mut T
+            195..199 'self': &B<T>
+            218..241 '{     ...     }': &T
+            228..235 '&self.0': &T
+            229..233 'self': &B<T>
+            229..235 'self.0': T
+            253..254 'a': A<i32>
+            264..310 '{     ...))); }': ()
+            274..275 't': &i32
+            278..279 'A': A<i32>(*mut i32) -> A<i32>
+            278..292 'A(0 as *mut _)': A<i32>
+            278..307 'A(0 as...B(a)))': &i32
+            280..281 '0': i32
+            280..291 '0 as *mut _': *mut i32
+            297..306 '&&B(B(a))': &&B<B<A<i32>>>
+            298..306 '&B(B(a))': &B<B<A<i32>>>
+            299..300 'B': B<B<A<i32>>>(B<A<i32>>) -> B<B<A<i32>>>
+            299..306 'B(B(a))': B<B<A<i32>>>
+            301..302 'B': B<A<i32>>(A<i32>) -> B<A<i32>>
+            301..305 'B(a)': B<A<i32>>
+            303..304 'a': A<i32>
         "#]],
     );
 }
@@ -1015,15 +981,15 @@ fn infer_method_argument_autoderef() {
 fn infer_in_elseif() {
     check_infer(
         r#"
-        struct Foo { field: i32 }
-        fn main(foo: Foo) {
-            if true {
+struct Foo { field: i32 }
+fn main(foo: Foo) {
+    if true {
 
-            } else if false {
-                foo.field
-            }
-        }
-        "#,
+    } else if false {
+        foo.field
+    }
+}
+"#,
         expect![[r#"
             34..37 'foo': Foo
             44..108 '{     ...   } }': ()
@@ -1043,28 +1009,29 @@ fn infer_in_elseif() {
 fn infer_if_match_with_return() {
     check_infer(
         r#"
-        fn foo() {
-            let _x1 = if true {
-                1
-            } else {
-                return;
-            };
-            let _x2 = if true {
-                2
-            } else {
-                return
-            };
-            let _x3 = match true {
-                true => 3,
-                _ => {
-                    return;
-                }
-            };
-            let _x4 = match true {
-                true => 4,
-                _ => return
-            };
-        }"#,
+fn foo() {
+    let _x1 = if true {
+        1
+    } else {
+        return;
+    };
+    let _x2 = if true {
+        2
+    } else {
+        return
+    };
+    let _x3 = match true {
+        true => 3,
+        _ => {
+            return;
+        }
+    };
+    let _x4 = match true {
+        true => 4,
+        _ => return
+    };
+}
+"#,
         expect![[r#"
             9..322 '{     ...  }; }': ()
             19..22 '_x1': i32
@@ -2639,11 +2606,8 @@ fn f() {
 fn infer_boxed_self_receiver() {
     check_infer(
         r#"
-#[lang = "deref"]
-pub trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
+//- minicore: deref
+use core::ops::Deref;
 
 struct Box<T>(T);
 
@@ -2675,40 +2639,39 @@ fn main() {
 }
         "#,
         expect![[r#"
-            67..71 'self': &Self
-            175..179 'self': &Box<T>
-            259..263 'self': &Box<Foo<T>>
-            289..291 '{}': ()
-            313..317 'self': &Box<Foo<T>>
-            346..348 '{}': ()
-            368..372 'self': Box<Foo<T>>
-            393..395 '{}': ()
-            409..630 '{     ...r(); }': ()
-            419..424 'boxed': Box<Foo<i32>>
-            427..430 'Box': Box<Foo<i32>>(Foo<i32>) -> Box<Foo<i32>>
-            427..442 'Box(Foo(0_i32))': Box<Foo<i32>>
-            431..434 'Foo': Foo<i32>(i32) -> Foo<i32>
-            431..441 'Foo(0_i32)': Foo<i32>
-            435..440 '0_i32': i32
-            453..457 'bad1': &i32
-            460..465 'boxed': Box<Foo<i32>>
-            460..477 'boxed....nner()': &i32
-            487..492 'good1': &i32
-            495..509 'Foo::get_inner': fn get_inner<i32>(&Box<Foo<i32>>) -> &i32
-            495..517 'Foo::g...boxed)': &i32
-            510..516 '&boxed': &Box<Foo<i32>>
-            511..516 'boxed': Box<Foo<i32>>
-            528..532 'bad2': &Foo<i32>
-            535..540 'boxed': Box<Foo<i32>>
-            535..551 'boxed....self()': &Foo<i32>
-            561..566 'good2': &Foo<i32>
-            569..582 'Foo::get_self': fn get_self<i32>(&Box<Foo<i32>>) -> &Foo<i32>
-            569..590 'Foo::g...boxed)': &Foo<i32>
-            583..589 '&boxed': &Box<Foo<i32>>
-            584..589 'boxed': Box<Foo<i32>>
-            601..606 'inner': Foo<i32>
-            609..614 'boxed': Box<Foo<i32>>
-            609..627 'boxed....nner()': Foo<i32>
+            104..108 'self': &Box<T>
+            188..192 'self': &Box<Foo<T>>
+            218..220 '{}': ()
+            242..246 'self': &Box<Foo<T>>
+            275..277 '{}': ()
+            297..301 'self': Box<Foo<T>>
+            322..324 '{}': ()
+            338..559 '{     ...r(); }': ()
+            348..353 'boxed': Box<Foo<i32>>
+            356..359 'Box': Box<Foo<i32>>(Foo<i32>) -> Box<Foo<i32>>
+            356..371 'Box(Foo(0_i32))': Box<Foo<i32>>
+            360..363 'Foo': Foo<i32>(i32) -> Foo<i32>
+            360..370 'Foo(0_i32)': Foo<i32>
+            364..369 '0_i32': i32
+            382..386 'bad1': &i32
+            389..394 'boxed': Box<Foo<i32>>
+            389..406 'boxed....nner()': &i32
+            416..421 'good1': &i32
+            424..438 'Foo::get_inner': fn get_inner<i32>(&Box<Foo<i32>>) -> &i32
+            424..446 'Foo::g...boxed)': &i32
+            439..445 '&boxed': &Box<Foo<i32>>
+            440..445 'boxed': Box<Foo<i32>>
+            457..461 'bad2': &Foo<i32>
+            464..469 'boxed': Box<Foo<i32>>
+            464..480 'boxed....self()': &Foo<i32>
+            490..495 'good2': &Foo<i32>
+            498..511 'Foo::get_self': fn get_self<i32>(&Box<Foo<i32>>) -> &Foo<i32>
+            498..519 'Foo::g...boxed)': &Foo<i32>
+            512..518 '&boxed': &Box<Foo<i32>>
+            513..518 'boxed': Box<Foo<i32>>
+            530..535 'inner': Foo<i32>
+            538..543 'boxed': Box<Foo<i32>>
+            538..556 'boxed....nner()': Foo<i32>
         "#]],
     );
 }
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index c830e576e..65fed02d2 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -6,10 +6,10 @@ use super::{check_infer, check_infer_with_mismatches, check_types};
 fn infer_await() {
     check_types(
         r#"
-//- /main.rs crate:main deps:core
+//- minicore: future
 struct IntFuture;
 
-impl Future for IntFuture {
+impl core::future::Future for IntFuture {
     type Output = u64;
 }
 
@@ -18,16 +18,6 @@ fn test() {
     let v = r.await;
     v;
 } //^ u64
-
-//- /core.rs crate:core
-pub mod prelude {
-    pub mod rust_2018 {
-        #[lang = "future_trait"]
-        pub trait Future {
-            type Output;
-        }
-    }
-}
 "#,
     );
 }
@@ -36,25 +26,14 @@ pub mod prelude {
 fn infer_async() {
     check_types(
         r#"
-//- /main.rs crate:main deps:core
-async fn foo() -> u64 {
-            128
-}
+//- minicore: future
+async fn foo() -> u64 { 128 }
 
 fn test() {
     let r = foo();
     let v = r.await;
     v;
 } //^ u64
-
-//- /core.rs crate:core
-#[prelude_import] use future::*;
-mod future {
-    #[lang = "future_trait"]
-    trait Future {
-        type Output;
-    }
-}
 "#,
     );
 }
@@ -63,24 +42,13 @@ mod future {
 fn infer_desugar_async() {
     check_types(
         r#"
-//- /main.rs crate:main deps:core
-async fn foo() -> u64 {
-            128
-}
+//- minicore: future
+async fn foo() -> u64 { 128 }
 
 fn test() {
     let r = foo();
     r;
 } //^ impl Future<Output = u64>
-
-//- /core.rs crate:core
-#[prelude_import] use future::*;
-mod future {
-    trait Future {
-        type Output;
-    }
-}
-
 "#,
     );
 }
@@ -89,7 +57,7 @@ mod future {
 fn infer_async_block() {
     check_types(
         r#"
-//- /main.rs crate:main deps:core
+//- minicore: future, option
 async fn test() {
     let a = async { 42 };
     a;
@@ -101,7 +69,7 @@ async fn test() {
     b;
 //  ^ ()
     let c = async {
-        let y = Option::None;
+        let y = None;
         y
     //  ^ Option<u64>
     };
@@ -109,18 +77,6 @@ async fn test() {
     c;
 //  ^ impl Future<Output = Option<u64>>
 }
-
-enum Option<T> { None, Some(T) }
-
-//- /core.rs crate:core
-#[prelude_import] use future::*;
-mod future {
-    #[lang = "future_trait"]
-    trait Future {
-        type Output;
-    }
-}
-
 "#,
     );
 }
@@ -704,14 +660,9 @@ mod ops {
 fn deref_trait() {
     check_types(
         r#"
-#[lang = "deref"]
-trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
-
+//- minicore: deref
 struct Arc<T>;
-impl<T> Deref for Arc<T> {
+impl<T> core::ops::Deref for Arc<T> {
     type Target = T;
 }
 
@@ -731,16 +682,10 @@ fn test(s: Arc<S>) {
 fn deref_trait_with_inference_var() {
     check_types(
         r#"
-//- /main.rs
-#[lang = "deref"]
-trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
-
+//- minicore: deref
 struct Arc<T>;
 fn new_arc<T>() -> Arc<T> {}
-impl<T> Deref for Arc<T> {
+impl<T> core::ops::Deref for Arc<T> {
     type Target = T;
 }
 
@@ -761,15 +706,10 @@ fn test() {
 fn deref_trait_infinite_recursion() {
     check_types(
         r#"
-#[lang = "deref"]
-trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
-
+//- minicore: deref
 struct S;
 
-impl Deref for S {
+impl core::ops::Deref for S {
     type Target = S;
 }
 
@@ -784,14 +724,9 @@ fn test(s: S) {
 fn deref_trait_with_question_mark_size() {
     check_types(
         r#"
-#[lang = "deref"]
-trait Deref {
-    type Target;
-    fn deref(&self) -> &Self::Target;
-}
-
+//- minicore: deref
 struct Arc<T>;
-impl<T> Deref for Arc<T> {
+impl<T: ?Sized> core::ops::Deref for Arc<T> {
     type Target = T;
 }
 
@@ -2625,12 +2560,9 @@ fn test<T: Trait>() {
 fn dyn_trait_through_chalk() {
     check_types(
         r#"
+//- minicore: deref
 struct Box<T> {}
-#[lang = "deref"]
-trait Deref {
-    type Target;
-}
-impl<T> Deref for Box<T> {
+impl<T> core::ops::Deref for Box<T> {
     type Target = T;
 }
 trait Trait {
@@ -3695,16 +3627,7 @@ impl foo::Foo for u32 {
 fn infer_async_ret_type() {
     check_types(
         r#"
-//- /main.rs crate:main deps:core
-
-enum Result<T, E> {
-    Ok(T),
-    Err(E),
-}
-
-use Result::*;
-
-
+//- minicore: future, result
 struct Fooey;
 
 impl Fooey {
@@ -3727,15 +3650,6 @@ async fn get_accounts() -> Result<u32, ()> {
     //                      ^ u32
     Ok(ret)
 }
-
-//- /core.rs crate:core
-#[prelude_import] use future::*;
-mod future {
-    #[lang = "future_trait"]
-    trait Future {
-        type Output;
-    }
-}
 "#,
     );
 }
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index afeded315..14cf94d60 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -3000,29 +3000,24 @@ fn foo(ar$0g: &impl Foo + Bar<S>) {}
     fn test_hover_async_block_impl_trait_has_goto_type_action() {
         check_actions(
             r#"
+//- minicore: future
 struct S;
 fn foo() {
     let fo$0o = async { S };
 }
-
-#[prelude_import] use future::*;
-mod future {
-    #[lang = "future_trait"]
-    pub trait Future { type Output; }
-}
 "#,
             expect![[r#"
                 [
                     GoToType(
                         [
                             HoverGotoTypeData {
-                                mod_path: "test::future::Future",
+                                mod_path: "core::future::Future",
                                 nav: NavigationTarget {
                                     file_id: FileId(
-                                        0,
+                                        1,
                                     ),
-                                    full_range: 101..163,
-                                    focus_range: 140..146,
+                                    full_range: 244..426,
+                                    focus_range: 283..289,
                                     name: "Future",
                                     kind: Trait,
                                     description: "pub trait Future",
diff --git a/crates/ide_completion/src/completions/keyword.rs b/crates/ide_completion/src/completions/keyword.rs
index ba13d3707..0fccbeccf 100644
--- a/crates/ide_completion/src/completions/keyword.rs
+++ b/crates/ide_completion/src/completions/keyword.rs
@@ -536,17 +536,11 @@ Some multi-line comment$0
     fn test_completion_await_impls_future() {
         check(
             r#"
-//- /main.rs crate:main deps:std
-use std::future::*;
+//- minicore: future
+use core::future::*;
 struct A {}
 impl Future for A {}
 fn foo(a: A) { a.$0 }
-
-//- /std/lib.rs crate:std
-pub mod future {
-    #[lang = "future_trait"]
-    pub trait Future {}
-}
 "#,
             expect![[r#"
                 kw await expr.await
@@ -555,20 +549,12 @@ pub mod future {
 
         check(
             r#"
-//- /main.rs crate:main deps:std
+//- minicore: future
 use std::future::*;
 fn foo() {
     let a = async {};
     a.$0
 }
-
-//- /std/lib.rs crate:std
-pub mod future {
-    #[lang = "future_trait"]
-    pub trait Future {
-        type Output;
-    }
-}
 "#,
             expect![[r#"
                 kw await expr.await
diff --git a/crates/ide_completion/src/render.rs b/crates/ide_completion/src/render.rs
index d8ca18c73..3eb51e80b 100644
--- a/crates/ide_completion/src/render.rs
+++ b/crates/ide_completion/src/render.rs
@@ -1152,16 +1152,11 @@ fn main() {
     fn suggest_deref() {
         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 {
@@ -1185,8 +1180,9 @@ fn main() {
                 st T []
                 st S []
                 fn main() []
-                tt Deref []
                 fn foo(…) []
+                md core []
+                tt Sized []
             "#]],
         )
     }
diff --git a/crates/rust-analyzer/tests/slow-tests/support.rs b/crates/rust-analyzer/tests/slow-tests/support.rs
index e22c295f9..260a504e7 100644
--- a/crates/rust-analyzer/tests/slow-tests/support.rs
+++ b/crates/rust-analyzer/tests/slow-tests/support.rs
@@ -75,7 +75,9 @@ impl<'a> Project<'a> {
             profile::init_from(crate::PROFILE);
         });
 
-        for entry in Fixture::parse(self.fixture) {
+        let (mini_core, fixtures) = Fixture::parse(self.fixture);
+        assert!(mini_core.is_none());
+        for entry in fixtures {
             let path = tmp_dir.path().join(&entry.path['/'.len_utf8()..]);
             fs::create_dir_all(path.parent().unwrap()).unwrap();
             fs::write(path.as_path(), entry.text.as_bytes()).unwrap();
diff --git a/crates/test_utils/src/fixture.rs b/crates/test_utils/src/fixture.rs
index d0bddf7d8..6ba112de8 100644
--- a/crates/test_utils/src/fixture.rs
+++ b/crates/test_utils/src/fixture.rs
@@ -77,6 +77,11 @@ pub struct Fixture {
     pub introduce_new_source_root: bool,
 }
 
+pub struct MiniCore {
+    activated_flags: Vec<String>,
+    valid_flags: Vec<String>,
+}
+
 impl Fixture {
     /// Parses text which looks like this:
     ///
@@ -86,12 +91,28 @@ impl Fixture {
     ///  line 2
     ///  //- other meta
     ///  ```
-    pub fn parse(ra_fixture: &str) -> Vec<Fixture> {
+    ///
+    /// Fixture can also start with a minicore declaration:
+    ///
+    /// ```
+    /// //- minicore: sized
+    /// ```
+    ///
+    /// That will include a subset of `libcore` into the fixture, see
+    /// `minicore.rs` for what's available.
+    pub fn parse(ra_fixture: &str) -> (Option<MiniCore>, Vec<Fixture>) {
         let fixture = trim_indent(ra_fixture);
-
+        let mut fixture = fixture.as_str();
+        let mut mini_core = None;
         let mut res: Vec<Fixture> = Vec::new();
 
-        let default = if ra_fixture.contains("//-") { None } else { Some("//- /main.rs") };
+        if fixture.starts_with("//- minicore:") {
+            let first_line = fixture.split_inclusive('\n').next().unwrap();
+            mini_core = Some(MiniCore::parse(first_line));
+            fixture = &fixture[first_line.len()..];
+        }
+
+        let default = if fixture.contains("//-") { None } else { Some("//- /main.rs") };
 
         for (ix, line) in default.into_iter().chain(fixture.split_inclusive('\n')).enumerate() {
             if line.contains("//-") {
@@ -113,7 +134,7 @@ impl Fixture {
             }
         }
 
-        res
+        (mini_core, res)
     }
 
     //- /lib.rs crate:foo deps:bar,baz cfg:foo=a,bar=b env:OUTDIR=path/to,OTHER=foo
@@ -172,6 +193,133 @@ impl Fixture {
     }
 }
 
+impl MiniCore {
+    fn has_flag(&self, flag: &str) -> bool {
+        self.activated_flags.iter().any(|it| it == flag)
+    }
+
+    #[track_caller]
+    fn assert_valid_flag(&self, flag: &str) {
+        if !self.valid_flags.iter().any(|it| it == flag) {
+            panic!("invalid flag: {:?}, valid flags: {:?}", flag, self.valid_flags);
+        }
+    }
+
+    fn parse(line: &str) -> MiniCore {
+        let mut res = MiniCore { activated_flags: Vec::new(), valid_flags: Vec::new() };
+
+        let line = line.strip_prefix("//- minicore:").unwrap().trim();
+        for entry in line.split(", ") {
+            if res.has_flag(entry) {
+                panic!("duplicate minicore flag: {:?}", entry)
+            }
+            res.activated_flags.push(entry.to_string())
+        }
+
+        res
+    }
+
+    /// Strips parts of minicore.rs which are flagged by inactive flags.
+    ///
+    /// This is probably over-engineered to support flags dependencies.
+    pub fn source_code(mut self) -> String {
+        let mut buf = String::new();
+        let raw_mini_core = include_str!("./minicore.rs");
+        let mut lines = raw_mini_core.split_inclusive('\n');
+
+        let mut parsing_flags = false;
+        let mut implications = Vec::new();
+
+        // Parse `//!` preamble and extract flags and dependencies.
+        for line in lines.by_ref() {
+            let line = match line.strip_prefix("//!") {
+                Some(it) => it,
+                None => {
+                    assert!(line.trim().is_empty());
+                    break;
+                }
+            };
+
+            if parsing_flags {
+                let (flag, deps) = line.split_once(':').unwrap();
+                let flag = flag.trim();
+                self.valid_flags.push(flag.to_string());
+                for dep in deps.split(", ") {
+                    let dep = dep.trim();
+                    if !dep.is_empty() {
+                        self.assert_valid_flag(dep);
+                        implications.push((flag, dep));
+                    }
+                }
+            }
+
+            if line.contains("Available flags:") {
+                parsing_flags = true;
+            }
+        }
+
+        for flag in &self.activated_flags {
+            self.assert_valid_flag(flag);
+        }
+
+        // Fixed point loop to compute transitive closure of flags.
+        loop {
+            let mut changed = false;
+            for &(u, v) in implications.iter() {
+                if self.has_flag(u) && !self.has_flag(v) {
+                    self.activated_flags.push(v.to_string());
+                    changed = true;
+                }
+            }
+            if !changed {
+                break;
+            }
+        }
+
+        let mut curr_region = "";
+        let mut seen_regions = Vec::new();
+        for line in lines {
+            let trimmed = line.trim();
+            if let Some(region) = trimmed.strip_prefix("// region:") {
+                assert_eq!(curr_region, "");
+                curr_region = region;
+                continue;
+            }
+            if let Some(region) = trimmed.strip_prefix("// endregion:") {
+                assert_eq!(curr_region, region);
+                curr_region = "";
+                continue;
+            }
+            seen_regions.push(curr_region);
+
+            let mut flag = curr_region;
+            if let Some(idx) = trimmed.find("// :") {
+                flag = &trimmed[idx + "// :".len()..];
+            }
+
+            let skip = if flag == "" {
+                false
+            } else {
+                assert!(!flag.starts_with(' '), "region marker starts with a space: {:?}", flag);
+                self.assert_valid_flag(flag);
+                !self.has_flag(flag)
+            };
+
+            if !skip {
+                buf.push_str(line)
+            }
+        }
+
+        for flag in &self.valid_flags {
+            if !seen_regions.iter().any(|it| it == flag) {
+                panic!("unused minicore flag: {:?}", flag);
+            }
+        }
+
+        buf
+    }
+}
+
 #[test]
 #[should_panic]
 fn parse_fixture_checks_further_indented_metadata() {
@@ -189,12 +337,14 @@ fn parse_fixture_checks_further_indented_metadata() {
 
 #[test]
 fn parse_fixture_gets_full_meta() {
-    let parsed = Fixture::parse(
-        r"
-    //- /lib.rs crate:foo deps:bar,baz cfg:foo=a,bar=b,atom env:OUTDIR=path/to,OTHER=foo
-    mod m;
-    ",
+    let (mini_core, parsed) = Fixture::parse(
+        r#"
+//- minicore: coerce_unsized
+//- /lib.rs crate:foo deps:bar,baz cfg:foo=a,bar=b,atom env:OUTDIR=path/to,OTHER=foo
+mod m;
+"#,
     );
+    assert_eq!(mini_core.unwrap().activated_flags, vec!["coerce_unsized".to_string()]);
     assert_eq!(1, parsed.len());
 
     let meta = &parsed[0];
diff --git a/crates/test_utils/src/lib.rs b/crates/test_utils/src/lib.rs
index b2fe25f82..d55bae62a 100644
--- a/crates/test_utils/src/lib.rs
+++ b/crates/test_utils/src/lib.rs
@@ -23,7 +23,10 @@ use text_size::{TextRange, TextSize};
 pub use dissimilar::diff as __diff;
 pub use rustc_hash::FxHashMap;
 
-pub use crate::{assert_linear::AssertLinear, fixture::Fixture};
+pub use crate::{
+    assert_linear::AssertLinear,
+    fixture::{Fixture, MiniCore},
+};
 
 pub const CURSOR_MARKER: &str = "$0";
 pub const ESCAPED_CURSOR_MARKER: &str = "\\$0";
diff --git a/crates/test_utils/src/minicore.rs b/crates/test_utils/src/minicore.rs
new file mode 100644
index 000000000..5ff60178c
--- /dev/null
+++ b/crates/test_utils/src/minicore.rs
@@ -0,0 +1,204 @@
+//! This is a fixture we use for tests that need lang items.
+//!
+//! We want to include the minimal subset of core for each test, so this file
+//! supports "conditional compilation". Tests use the following syntax to include minicore:
+//!
+//!  //- minicore: flag1, flag2
+//!
+//! We then strip all the code marked with other flags.
+//!
+//! Available flags:
+//!     sized:
+//!     slice:
+//!     range:
+//!     unsize: sized
+//!     deref: sized
+//!     coerce_unsized: unsize
+//!     pin:
+//!     future: pin
+//!     option:
+//!     result:
+
+pub mod marker {
+    // region:sized
+    #[lang = "sized"]
+    #[fundamental]
+    #[rustc_specialization_trait]
+    pub trait Sized {}
+    // endregion:sized
+
+    // region:unsize
+    #[lang = "unsize"]
+    pub trait Unsize<T: ?Sized> {}
+    // endregion:unsize
+}
+
+pub mod ops {
+    // region:coerce_unsized
+    mod unsize {
+        use crate::marker::Unsize;
+
+        #[lang = "coerce_unsized"]
+        pub trait CoerceUnsized<T: ?Sized> {}
+
+        impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a mut U> for &'a mut T {}
+        impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b mut T {}
+        impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for &'a mut T {}
+        impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a mut T {}
+
+        impl<'a, 'b: 'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<&'a U> for &'b T {}
+        impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for &'a T {}
+
+        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*mut U> for *mut T {}
+        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *mut T {}
+        impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}
+    }
+    pub use self::unsize::CoerceUnsized;
+    // endregion:coerce_unsized
+
+    // region:deref
+    mod deref {
+        #[lang = "deref"]
+        pub trait Deref {
+            #[lang = "deref_target"]
+            type Target: ?Sized;
+            fn deref(&self) -> &Self::Target;
+        }
+    }
+    pub use self::deref::Deref;
+    // endregion:deref
+
+    // region:range
+    mod range {
+        #[lang = "RangeFull"]
+        pub struct RangeFull;
+
+        #[lang = "Range"]
+        pub struct Range<Idx> {
+            pub start: Idx,
+            pub end: Idx,
+        }
+
+        #[lang = "RangeFrom"]
+        pub struct RangeFrom<Idx> {
+            pub start: Idx,
+        }
+
+        #[lang = "RangeTo"]
+        pub struct RangeTo<Idx> {
+            pub end: Idx,
+        }
+
+        #[lang = "RangeInclusive"]
+        pub struct RangeInclusive<Idx> {
+            pub(crate) start: Idx,
+            pub(crate) end: Idx,
+            pub(crate) exhausted: bool,
+        }
+
+        #[lang = "RangeToInclusive"]
+        pub struct RangeToInclusive<Idx> {
+            pub end: Idx,
+        }
+    }
+    pub use self::range::{Range, RangeFrom, RangeFull, RangeTo};
+    pub use self::range::{RangeInclusive, RangeToInclusive};
+    // endregion:range
+}
+
+// region:slice
+pub mod slice {
+    #[lang = "slice"]
+    impl<T> [T] {
+        pub fn len(&self) -> usize {
+            loop {}
+        }
+    }
+}
+// endregion:slice
+
+// region:option
+pub mod option {
+    pub enum Option<T> {
+        #[lang = "None"]
+        None,
+        #[lang = "Some"]
+        Some(T),
+    }
+}
+// endregion:option
+
+// region:result
+pub mod result {
+    pub enum Result<T, E> {
+        #[lang = "Ok"]
+        Ok(T),
+        #[lang = "Err"]
+        Err(E),
+    }
+}
+// endregion:result
+
+// region:pin
+pub mod pin {
+    #[lang = "pin"]
+    #[fundamental]
+    pub struct Pin<P> {
+        pointer: P,
+    }
+}
+// endregion:pin
+
+// region:future
+pub mod future {
+    use crate::{
+        pin::Pin,
+        task::{Context, Poll},
+    };
+
+    #[lang = "future_trait"]
+    pub trait Future {
+        type Output;
+        #[lang = "poll"]
+        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>;
+    }
+}
+pub mod task {
+    pub enum Poll<T> {
+        #[lang = "Ready"]
+        Ready(T),
+        #[lang = "Pending"]
+        Pending,
+    }
+
+    pub struct Context<'a> {
+        waker: &'a (),
+    }
+}
+// endregion:future
+
+pub mod prelude {
+    pub mod v1 {
+        pub use crate::{
+            marker::Sized,                      // :sized
+            option::Option::{self, None, Some}, // :option
+            result::Result::{self, Err, Ok},    // :result
+        };
+    }
+
+    pub mod rust_2015 {
+        pub use super::v1::*;
+    }
+
+    pub mod rust_2018 {
+        pub use super::v1::*;
+    }
+
+    pub mod rust_2021 {
+        pub use super::v1::*;
+    }
+}
+
+#[prelude_import]
+#[allow(unused)]
+use prelude::v1::*;