19 files changed, 359 insertions, 341 deletions

diff --git a/crates/ide_diagnostics/src/handlers/break_outside_of_loop.rs b/crates/ide_diagnostics/src/handlers/break_outside_of_loop.rs
index 5ad0fbd1b..d12594a4c 100644
--- a/crates/ide_diagnostics/src/handlers/break_outside_of_loop.rs
+++ b/crates/ide_diagnostics/src/handlers/break_outside_of_loop.rs
@@ -23,7 +23,7 @@ mod tests {
         check_diagnostics(
             r#"
 fn foo() { break; }
-         //^^^^^ break outside of loop
+         //^^^^^ error: break outside of loop
 "#,
         );
     }
diff --git a/crates/ide_diagnostics/src/field_shorthand.rs b/crates/ide_diagnostics/src/handlers/field_shorthand.rs
index 0b6af9965..33152e284 100644
--- a/crates/ide_diagnostics/src/field_shorthand.rs
+++ b/crates/ide_diagnostics/src/handlers/field_shorthand.rs
@@ -7,7 +7,7 @@ use text_edit::TextEdit;
 
 use crate::{fix, Diagnostic, Severity};
 
-pub(super) fn check(acc: &mut Vec<Diagnostic>, file_id: FileId, node: &SyntaxNode) {
+pub(crate) fn field_shorthand(acc: &mut Vec<Diagnostic>, file_id: FileId, node: &SyntaxNode) {
     match_ast! {
         match node {
             ast::RecordExpr(it) => check_expr_field_shorthand(acc, file_id, it),
diff --git a/crates/ide_diagnostics/src/handlers/inactive_code.rs b/crates/ide_diagnostics/src/handlers/inactive_code.rs
index 4b722fd64..dfd0e3351 100644
--- a/crates/ide_diagnostics/src/handlers/inactive_code.rs
+++ b/crates/ide_diagnostics/src/handlers/inactive_code.rs
@@ -49,26 +49,26 @@ fn f() {
     // The three g̶e̶n̶d̶e̶r̶s̶ statements:
 
     #[cfg(a)] fn f() {}  // Item statement
-  //^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+  //^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
     #[cfg(a)] {}         // Expression statement
-  //^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+  //^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
     #[cfg(a)] let x = 0; // let statement
-  //^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+  //^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
 
     abc(#[cfg(a)] 0);
-      //^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+      //^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
     let x = Struct {
         #[cfg(a)] f: 0,
-      //^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+      //^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
     };
     match () {
         () => (),
         #[cfg(a)] () => (),
-      //^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+      //^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
     }
 
     #[cfg(a)] 0          // Trailing expression of block
-  //^^^^^^^^^^^ code is inactive due to #[cfg] directives: a is disabled
+  //^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: a is disabled
 }
         "#,
         );
@@ -81,16 +81,16 @@ fn f() {
         check(
             r#"
     #[cfg(no)] pub fn f() {}
-  //^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: no is disabled
+  //^^^^^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: no is disabled
 
     #[cfg(no)] #[cfg(no2)] mod m;
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: no and no2 are disabled
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: no and no2 are disabled
 
     #[cfg(all(not(a), b))] enum E {}
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: b is disabled
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: b is disabled
 
     #[cfg(feature = "std")] use std;
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: feature = "std" is disabled
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: feature = "std" is disabled
 "#,
         );
     }
@@ -102,14 +102,14 @@ fn f() {
         check(
             r#"
     #[cfg_attr(not(never), cfg(no))] fn f() {}
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: no is disabled
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: no is disabled
 
     #[cfg_attr(not(never), cfg(not(no)))] fn f() {}
 
     #[cfg_attr(never, cfg(no))] fn g() {}
 
     #[cfg_attr(not(never), inline, cfg(no))] fn h() {}
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ code is inactive due to #[cfg] directives: no is disabled
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ weak: code is inactive due to #[cfg] directives: no is disabled
 "#,
         );
     }
diff --git a/crates/ide_diagnostics/src/handlers/incorrect_case.rs b/crates/ide_diagnostics/src/handlers/incorrect_case.rs
index 3a33029cf..72f251961 100644
--- a/crates/ide_diagnostics/src/handlers/incorrect_case.rs
+++ b/crates/ide_diagnostics/src/handlers/incorrect_case.rs
@@ -149,7 +149,7 @@ impl TestStruct {
         check_diagnostics(
             r#"
 fn FOO() {}
-// ^^^ Function `FOO` should have snake_case name, e.g. `foo`
+// ^^^ 💡 weak: Function `FOO` should have snake_case name, e.g. `foo`
 "#,
         );
         check_fix(r#"fn FOO$0() {}"#, r#"fn foo() {}"#);
@@ -160,7 +160,7 @@ fn FOO() {}
         check_diagnostics(
             r#"
 fn NonSnakeCaseName() {}
-// ^^^^^^^^^^^^^^^^ Function `NonSnakeCaseName` should have snake_case name, e.g. `non_snake_case_name`
+// ^^^^^^^^^^^^^^^^ 💡 weak: Function `NonSnakeCaseName` should have snake_case name, e.g. `non_snake_case_name`
 "#,
         );
     }
@@ -170,10 +170,10 @@ fn NonSnakeCaseName() {}
         check_diagnostics(
             r#"
 fn foo(SomeParam: u8) {}
-    // ^^^^^^^^^ Parameter `SomeParam` should have snake_case name, e.g. `some_param`
+    // ^^^^^^^^^ 💡 weak: Parameter `SomeParam` should have snake_case name, e.g. `some_param`
 
 fn foo2(ok_param: &str, CAPS_PARAM: u8) {}
-                     // ^^^^^^^^^^ Parameter `CAPS_PARAM` should have snake_case name, e.g. `caps_param`
+                     // ^^^^^^^^^^ 💡 weak: Parameter `CAPS_PARAM` should have snake_case name, e.g. `caps_param`
 "#,
         );
     }
@@ -184,9 +184,9 @@ fn foo2(ok_param: &str, CAPS_PARAM: u8) {}
             r#"
 fn foo() {
     let SOME_VALUE = 10;
-     // ^^^^^^^^^^ Variable `SOME_VALUE` should have snake_case name, e.g. `some_value`
+     // ^^^^^^^^^^ 💡 weak: Variable `SOME_VALUE` should have snake_case name, e.g. `some_value`
     let AnotherValue = 20;
-     // ^^^^^^^^^^^^ Variable `AnotherValue` should have snake_case name, e.g. `another_value`
+     // ^^^^^^^^^^^^ 💡 weak: Variable `AnotherValue` should have snake_case name, e.g. `another_value`
 }
 "#,
         );
@@ -197,10 +197,10 @@ fn foo() {
         check_diagnostics(
             r#"
 struct non_camel_case_name {}
-    // ^^^^^^^^^^^^^^^^^^^ Structure `non_camel_case_name` should have CamelCase name, e.g. `NonCamelCaseName`
+    // ^^^^^^^^^^^^^^^^^^^ 💡 weak: Structure `non_camel_case_name` should have CamelCase name, e.g. `NonCamelCaseName`
 
 struct SCREAMING_CASE {}
-    // ^^^^^^^^^^^^^^ Structure `SCREAMING_CASE` should have CamelCase name, e.g. `ScreamingCase`
+    // ^^^^^^^^^^^^^^ 💡 weak: Structure `SCREAMING_CASE` should have CamelCase name, e.g. `ScreamingCase`
 "#,
         );
     }
@@ -219,7 +219,7 @@ struct AABB {}
         check_diagnostics(
             r#"
 struct SomeStruct { SomeField: u8 }
-                 // ^^^^^^^^^ Field `SomeField` should have snake_case name, e.g. `some_field`
+                 // ^^^^^^^^^ 💡 weak: Field `SomeField` should have snake_case name, e.g. `some_field`
 "#,
         );
     }
@@ -229,10 +229,10 @@ struct SomeStruct { SomeField: u8 }
         check_diagnostics(
             r#"
 enum some_enum { Val(u8) }
-  // ^^^^^^^^^ Enum `some_enum` should have CamelCase name, e.g. `SomeEnum`
+  // ^^^^^^^^^ 💡 weak: Enum `some_enum` should have CamelCase name, e.g. `SomeEnum`
 
 enum SOME_ENUM {}
-  // ^^^^^^^^^ Enum `SOME_ENUM` should have CamelCase name, e.g. `SomeEnum`
+  // ^^^^^^^^^ 💡 weak: Enum `SOME_ENUM` should have CamelCase name, e.g. `SomeEnum`
 "#,
         );
     }
@@ -251,7 +251,7 @@ enum AABB {}
         check_diagnostics(
             r#"
 enum SomeEnum { SOME_VARIANT(u8) }
-             // ^^^^^^^^^^^^ Variant `SOME_VARIANT` should have CamelCase name, e.g. `SomeVariant`
+             // ^^^^^^^^^^^^ 💡 weak: Variant `SOME_VARIANT` should have CamelCase name, e.g. `SomeVariant`
 "#,
         );
     }
@@ -261,7 +261,7 @@ enum SomeEnum { SOME_VARIANT(u8) }
         check_diagnostics(
             r#"
 const some_weird_const: u8 = 10;
-   // ^^^^^^^^^^^^^^^^ Constant `some_weird_const` should have UPPER_SNAKE_CASE name, e.g. `SOME_WEIRD_CONST`
+   // ^^^^^^^^^^^^^^^^ 💡 weak: Constant `some_weird_const` should have UPPER_SNAKE_CASE name, e.g. `SOME_WEIRD_CONST`
 "#,
         );
     }
@@ -271,7 +271,7 @@ const some_weird_const: u8 = 10;
         check_diagnostics(
             r#"
 static some_weird_const: u8 = 10;
-    // ^^^^^^^^^^^^^^^^ Static variable `some_weird_const` should have UPPER_SNAKE_CASE name, e.g. `SOME_WEIRD_CONST`
+    // ^^^^^^^^^^^^^^^^ 💡 weak: Static variable `some_weird_const` should have UPPER_SNAKE_CASE name, e.g. `SOME_WEIRD_CONST`
 "#,
         );
     }
@@ -281,13 +281,13 @@ static some_weird_const: u8 = 10;
         check_diagnostics(
             r#"
 struct someStruct;
-    // ^^^^^^^^^^ Structure `someStruct` should have CamelCase name, e.g. `SomeStruct`
+    // ^^^^^^^^^^ 💡 weak: Structure `someStruct` should have CamelCase name, e.g. `SomeStruct`
 
 impl someStruct {
     fn SomeFunc(&self) {
-    // ^^^^^^^^ Function `SomeFunc` should have snake_case name, e.g. `some_func`
+    // ^^^^^^^^ 💡 weak: Function `SomeFunc` should have snake_case name, e.g. `some_func`
         let WHY_VAR_IS_CAPS = 10;
-         // ^^^^^^^^^^^^^^^ Variable `WHY_VAR_IS_CAPS` should have snake_case name, e.g. `why_var_is_caps`
+         // ^^^^^^^^^^^^^^^ 💡 weak: Variable `WHY_VAR_IS_CAPS` should have snake_case name, e.g. `why_var_is_caps`
     }
 }
 "#,
@@ -319,7 +319,7 @@ enum Option { Some, None }
 fn main() {
     match Option::None {
         SOME_VAR @ None => (),
-     // ^^^^^^^^ Variable `SOME_VAR` should have snake_case name, e.g. `some_var`
+     // ^^^^^^^^ 💡 weak: Variable `SOME_VAR` should have snake_case name, e.g. `some_var`
         Some => (),
     }
 }
@@ -421,11 +421,11 @@ extern {
         check_diagnostics(
             r#"
 trait BAD_TRAIT {
-    // ^^^^^^^^^ Trait `BAD_TRAIT` should have CamelCase name, e.g. `BadTrait`
+    // ^^^^^^^^^ 💡 weak: Trait `BAD_TRAIT` should have CamelCase name, e.g. `BadTrait`
     fn BAD_FUNCTION();
-    // ^^^^^^^^^^^^ Function `BAD_FUNCTION` should have snake_case name, e.g. `bad_function`
+    // ^^^^^^^^^^^^ 💡 weak: Function `BAD_FUNCTION` should have snake_case name, e.g. `bad_function`
     fn BadFunction();
-    // ^^^^^^^^^^^^ Function `BadFunction` should have snake_case name, e.g. `bad_function`
+    // ^^^^^^^^^^^^ 💡 weak: Function `BadFunction` should have snake_case name, e.g. `bad_function`
 }
     "#,
         );
diff --git a/crates/ide_diagnostics/src/handlers/macro_error.rs b/crates/ide_diagnostics/src/handlers/macro_error.rs
index d4d928ad1..356f089b2 100644
--- a/crates/ide_diagnostics/src/handlers/macro_error.rs
+++ b/crates/ide_diagnostics/src/handlers/macro_error.rs
@@ -27,7 +27,7 @@ mod tests {
 macro_rules! include { () => {} }
 
   include!("doesntexist");
-//^^^^^^^^^^^^^^^^^^^^^^^^ failed to load file `doesntexist`
+//^^^^^^^^^^^^^^^^^^^^^^^^ error: failed to load file `doesntexist`
             "#,
         );
     }
@@ -66,7 +66,7 @@ macro_rules! env { () => {} }
 macro_rules! concat { () => {} }
 
   include!(concat!(env!("OUT_DIR"), "/out.rs"));
-//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "run build scripts" to fix
+//^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: `OUT_DIR` not set, enable "run build scripts" to fix
 "#,
         );
     }
@@ -108,23 +108,23 @@ fn main() {
     // Test a handful of built-in (eager) macros:
 
     include!(invalid);
-  //^^^^^^^^^^^^^^^^^ could not convert tokens
+  //^^^^^^^^^^^^^^^^^ error: could not convert tokens
     include!("does not exist");
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^ failed to load file `does not exist`
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^ error: failed to load file `does not exist`
 
     env!(invalid);
-  //^^^^^^^^^^^^^ could not convert tokens
+  //^^^^^^^^^^^^^ error: could not convert tokens
 
     env!("OUT_DIR");
-  //^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "run build scripts" to fix
+  //^^^^^^^^^^^^^^^ error: `OUT_DIR` not set, enable "run build scripts" to fix
 
     compile_error!("compile_error works");
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ compile_error works
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: compile_error works
 
     // Lazy:
 
     format_args!();
-  //^^^^^^^^^^^^^^ no rule matches input tokens
+  //^^^^^^^^^^^^^^ error: no rule matches input tokens
 }
 "#,
         );
@@ -141,7 +141,7 @@ fn f() {
     m!();
 
     m!(hi);
-  //^^^^^^ leftover tokens
+  //^^^^^^ error: leftover tokens
 }
       "#,
         );
@@ -166,7 +166,7 @@ macro_rules! outer {
 
 fn f() {
     outer!();
-} //^^^^^^^^ leftover tokens
+} //^^^^^^^^ error: leftover tokens
 "#,
         )
     }
diff --git a/crates/ide_diagnostics/src/handlers/mismatched_arg_count.rs b/crates/ide_diagnostics/src/handlers/mismatched_arg_count.rs
index ce313b2cc..a9b6d3870 100644
--- a/crates/ide_diagnostics/src/handlers/mismatched_arg_count.rs
+++ b/crates/ide_diagnostics/src/handlers/mismatched_arg_count.rs
@@ -26,7 +26,7 @@ mod tests {
             r#"
 fn zero() {}
 fn f() { zero(1); }
-       //^^^^^^^ expected 0 arguments, found 1
+       //^^^^^^^ error: expected 0 arguments, found 1
 "#,
         );
 
@@ -44,7 +44,7 @@ fn f() { zero(); }
             r#"
 fn one(arg: u8) {}
 fn f() { one(); }
-       //^^^^^ expected 1 argument, found 0
+       //^^^^^ error: expected 1 argument, found 0
 "#,
         );
 
@@ -65,7 +65,7 @@ impl S { fn method(&self) {} }
 
 fn f() {
     S::method();
-} //^^^^^^^^^^^ expected 1 argument, found 0
+} //^^^^^^^^^^^ error: expected 1 argument, found 0
 "#,
         );
 
@@ -91,7 +91,7 @@ impl S { fn method(&self, arg: u8) {} }
 
             fn f() {
                 S.method();
-            } //^^^^^^^^^^ expected 1 argument, found 0
+            } //^^^^^^^^^^ error: expected 1 argument, found 0
             "#,
         );
 
@@ -131,7 +131,7 @@ fn f() {
 struct Tup(u8, u16);
 fn f() {
     Tup(0);
-} //^^^^^^ expected 2 arguments, found 1
+} //^^^^^^ error: expected 2 arguments, found 1
 "#,
         )
     }
@@ -143,7 +143,7 @@ fn f() {
 enum En { Variant(u8, u16), }
 fn f() {
     En::Variant(0);
-} //^^^^^^^^^^^^^^ expected 2 arguments, found 1
+} //^^^^^^^^^^^^^^ error: expected 2 arguments, found 1
 "#,
         )
     }
@@ -162,9 +162,9 @@ impl Foo {
     fn new() {
         Foo::Bar(0);
         Foo::Bar(0, 1);
-      //^^^^^^^^^^^^^^ expected 1 argument, found 2
+      //^^^^^^^^^^^^^^ error: expected 1 argument, found 2
         Foo::Bar();
-      //^^^^^^^^^^ expected 1 argument, found 0
+      //^^^^^^^^^^ error: expected 1 argument, found 0
     }
 }
         "#,
@@ -185,7 +185,7 @@ fn f() {
     unsafe {
         fixed(0);
         fixed(0, 1);
-      //^^^^^^^^^^^ expected 1 argument, found 2
+      //^^^^^^^^^^^ error: expected 1 argument, found 2
         varargs(0);
         varargs(0, 1);
         varargs2();
@@ -204,10 +204,10 @@ fn f() {
 fn main() {
     let f = |()| ();
     f();
-  //^^^ expected 1 argument, found 0
+  //^^^ error: expected 1 argument, found 0
     f(());
     f((), ());
-  //^^^^^^^^^ expected 1 argument, found 2
+  //^^^^^^^^^ error: expected 1 argument, found 2
 }
 "#,
         )
diff --git a/crates/ide_diagnostics/src/handlers/missing_fields.rs b/crates/ide_diagnostics/src/handlers/missing_fields.rs
index bc82c0e4a..bc56e0342 100644
--- a/crates/ide_diagnostics/src/handlers/missing_fields.rs
+++ b/crates/ide_diagnostics/src/handlers/missing_fields.rs
@@ -19,7 +19,7 @@ use crate::{fix, Diagnostic, DiagnosticsContext};
 // let a = A { a: 10 };
 // ```
 pub(crate) fn missing_fields(ctx: &DiagnosticsContext<'_>, d: &hir::MissingFields) -> Diagnostic {
-    let mut message = String::from("Missing structure fields:\n");
+    let mut message = String::from("missing structure fields:\n");
     for field in &d.missed_fields {
         format_to!(message, "- {}\n", field);
     }
@@ -85,7 +85,7 @@ mod tests {
 struct S { foo: i32, bar: () }
 fn baz(s: S) {
     let S { foo: _ } = s;
-      //^ Missing structure fields:
+      //^ error: missing structure fields:
       //| - bar
 }
 "#,
@@ -323,4 +323,33 @@ fn f() {
 "#,
         );
     }
+
+    #[test]
+    fn import_extern_crate_clash_with_inner_item() {
+        // This is more of a resolver test, but doesn't really work with the hir_def testsuite.
+
+        check_diagnostics(
+            r#"
+//- /lib.rs crate:lib deps:jwt
+mod permissions;
+
+use permissions::jwt;
+
+fn f() {
+    fn inner() {}
+    jwt::Claims {}; // should resolve to the local one with 0 fields, and not get a diagnostic
+}
+
+//- /permissions.rs
+pub mod jwt  {
+    pub struct Claims {}
+}
+
+//- /jwt/lib.rs crate:jwt
+pub struct Claims {
+    field: u8,
+}
+        "#,
+        );
+    }
 }
diff --git a/crates/ide_diagnostics/src/handlers/missing_match_arms.rs b/crates/ide_diagnostics/src/handlers/missing_match_arms.rs
index 9ea533d74..947b0f2e2 100644
--- a/crates/ide_diagnostics/src/handlers/missing_match_arms.rs
+++ b/crates/ide_diagnostics/src/handlers/missing_match_arms.rs
@@ -31,9 +31,9 @@ mod tests {
             r#"
 fn main() {
     match () { }
-        //^^ missing match arm
+        //^^ error: missing match arm
     match (()) { }
-        //^^^^ missing match arm
+        //^^^^ error: missing match arm
 
     match () { _ => (), }
     match () { () => (), }
@@ -49,7 +49,7 @@ fn main() {
             r#"
 fn main() {
     match ((), ()) { }
-        //^^^^^^^^ missing match arm
+        //^^^^^^^^ error: missing match arm
 
     match ((), ()) { ((), ()) => (), }
 }
@@ -63,21 +63,21 @@ fn main() {
             r#"
 fn test_main() {
     match false { }
-        //^^^^^ missing match arm
+        //^^^^^ error: missing match arm
     match false { true => (), }
-        //^^^^^ missing match arm
+        //^^^^^ error: missing match arm
     match (false, true) {}
-        //^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^ error: missing match arm
     match (false, true) { (true, true) => (), }
-        //^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^ error: missing match arm
     match (false, true) {
-        //^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^ error: missing match arm
         (false, true) => (),
         (false, false) => (),
         (true, false) => (),
     }
     match (false, true) { (true, _x) => (), }
-        //^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^ error: missing match arm
 
     match false { true => (), false => (), }
     match (false, true) {
@@ -116,11 +116,11 @@ fn test_main() {
             r#"
 fn main() {
     match (false, ((), false)) {}
-        //^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^ error: missing match arm
     match (false, ((), false)) { (true, ((), true)) => (), }
-        //^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^ error: missing match arm
     match (false, ((), false)) { (true, _) => (), }
-        //^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^ error: missing match arm
 
     match (false, ((), false)) {
         (true, ((), true)) => (),
@@ -146,12 +146,12 @@ enum Either { A, B, }
 
 fn main() {
     match Either::A { }
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
     match Either::B { Either::A => (), }
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
 
     match &Either::B {
-        //^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^ error: missing match arm
         Either::A => (),
     }
 
@@ -174,9 +174,9 @@ enum Either { A(bool), B }
 
 fn main() {
     match Either::B { }
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
     match Either::B {
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
         Either::A(true) => (), Either::B => ()
     }
 
@@ -207,7 +207,7 @@ enum Either { A(bool), B(bool, bool) }
 
 fn main() {
     match Either::A(false) {
-        //^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^ error: missing match arm
         Either::A(_) => (),
         Either::B(false, _) => (),
     }
@@ -352,7 +352,7 @@ fn main() {
         Either::A => (),
     }
     match loop { break Foo::A } {
-        //^^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^^ error: missing match arm
         Either::A => (),
     }
     match loop { break Foo::A } {
@@ -390,19 +390,19 @@ enum Either { A { foo: bool }, B }
 fn main() {
     let a = Either::A { foo: true };
     match a { }
-        //^ missing match arm
+        //^ error: missing match arm
     match a { Either::A { foo: true } => () }
-        //^ missing match arm
+        //^ error: missing match arm
     match a {
         Either::A { } => (),
-      //^^^^^^^^^ Missing structure fields:
+      //^^^^^^^^^ error: missing structure fields:
       //        | - foo
         Either::B => (),
     }
     match a {
-        //^ missing match arm
+        //^ error: missing match arm
         Either::A { } => (),
-    } //^^^^^^^^^ Missing structure fields:
+    } //^^^^^^^^^ error: missing structure fields:
       //        | - foo
 
     match a {
@@ -431,7 +431,7 @@ enum Either {
 fn main() {
     let a = Either::A { foo: true, bar: () };
     match a {
-        //^ missing match arm
+        //^ error: missing match arm
         Either::A { bar: (), foo: false } => (),
         Either::A { foo: true, bar: () } => (),
     }
@@ -458,12 +458,12 @@ enum Either {
 fn main() {
     let a = Either::B;
     match a {
-        //^ missing match arm
+        //^ error: missing match arm
         Either::A { foo: true, .. } => (),
         Either::B => (),
     }
     match a {
-        //^ missing match arm
+        //^ error: missing match arm
         Either::A { .. } => (),
     }
 
@@ -493,14 +493,14 @@ enum Either {
 
 fn main() {
     match Either::B {
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
         Either::A(true, .., true) => (),
         Either::A(true, .., false) => (),
         Either::A(false, .., false) => (),
         Either::B => (),
     }
     match Either::B {
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
         Either::A(true, .., true) => (),
         Either::A(true, .., false) => (),
         Either::A(.., true) => (),
@@ -537,7 +537,7 @@ fn enum_(never: Never) {
 }
 fn enum_ref(never: &Never) {
     match never {}
-        //^^^^^ missing match arm
+        //^^^^^ error: missing match arm
 }
 fn bang(never: !) {
     match never {}
@@ -561,7 +561,7 @@ fn main() {
         Some(never) => match never {},
     }
     match Option::<Never>::None {
-        //^^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^^ error: missing match arm
         Option::Some(_never) => {},
     }
 }
@@ -575,7 +575,7 @@ fn main() {
             r#"
 fn main() {
     match (false, true, false) {
-        //^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^ error: missing match arm
         (false, ..) => (),
     }
 }"#,
@@ -588,7 +588,7 @@ fn main() {
             r#"
 fn main() {
     match (false, true, false) {
-        //^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^ error: missing match arm
         (.., false) => (),
     }
 }"#,
@@ -601,7 +601,7 @@ fn main() {
             r#"
 fn main() {
     match (false, true, false) {
-        //^^^^^^^^^^^^^^^^^^^^ missing match arm
+        //^^^^^^^^^^^^^^^^^^^^ error: missing match arm
         (true, .., false) => (),
     }
 }"#,
@@ -614,11 +614,11 @@ fn main() {
             r#"struct Foo { a: bool }
 fn main(f: Foo) {
     match f {}
-        //^ missing match arm
+        //^ error: missing match arm
     match f { Foo { a: true } => () }
-        //^ missing match arm
+        //^ error: missing match arm
     match &f { Foo { a: true } => () }
-        //^^ missing match arm
+        //^^ error: missing match arm
     match f { Foo { a: _ } => () }
     match f {
         Foo { a: true } => (),
@@ -639,9 +639,9 @@ fn main(f: Foo) {
             r#"struct Foo(bool);
 fn main(f: Foo) {
     match f {}
-        //^ missing match arm
+        //^ error: missing match arm
     match f { Foo(true) => () }
-        //^ missing match arm
+        //^ error: missing match arm
     match f {
         Foo(true) => (),
         Foo(false) => (),
@@ -657,7 +657,7 @@ fn main(f: Foo) {
             r#"struct Foo;
 fn main(f: Foo) {
     match f {}
-        //^ missing match arm
+        //^ error: missing match arm
     match f { Foo => () }
 }
 "#,
@@ -670,9 +670,9 @@ fn main(f: Foo) {
             r#"struct Foo { foo: bool, bar: bool }
 fn main(f: Foo) {
     match f { Foo { foo: true, .. } => () }
-        //^ missing match arm
+        //^ error: missing match arm
     match f {
-        //^ missing match arm
+        //^ error: missing match arm
         Foo { foo: true, .. } => (),
         Foo { bar: false, .. } => ()
     }
@@ -693,7 +693,7 @@ fn main(f: Foo) {
 fn main() {
     enum Either { A(bool), B }
     match Either::B {
-        //^^^^^^^^^ missing match arm
+        //^^^^^^^^^ error: missing match arm
         Either::A(true | false) => (),
     }
 }
@@ -715,7 +715,7 @@ fn main(v: S) {
     match v { S{..}       => {} }
     match v { _           => {} }
     match v { }
-        //^ missing match arm
+        //^ error: missing match arm
 }
 "#,
         );
@@ -731,7 +731,7 @@ fn main() {
         false     => {}
     }
     match true { _x @ true => {} }
-        //^^^^ missing match arm
+        //^^^^ error: missing match arm
 }
 "#,
         );
@@ -786,12 +786,12 @@ use lib::E;
 fn main() {
     match E::A { _ => {} }
     match E::A {
-        //^^^^ missing match arm
+        //^^^^ error: missing match arm
         E::A => {}
         E::B => {}
     }
     match E::A {
-        //^^^^ missing match arm
+        //^^^^ error: missing match arm
         E::A | E::B => {}
     }
 }
@@ -810,7 +810,7 @@ fn main() {
         false         => {}
     }
     match true {
-        //^^^^ missing match arm
+        //^^^^ error: missing match arm
         true if false => {}
         false         => {}
     }
diff --git a/crates/ide_diagnostics/src/handlers/missing_unsafe.rs b/crates/ide_diagnostics/src/handlers/missing_unsafe.rs
index 62d8687ba..7acd9228a 100644
--- a/crates/ide_diagnostics/src/handlers/missing_unsafe.rs
+++ b/crates/ide_diagnostics/src/handlers/missing_unsafe.rs
@@ -23,7 +23,7 @@ fn main() {
     let x = &5 as *const usize;
     unsafe { let y = *x; }
     let z = *x;
-}         //^^ this operation is unsafe and requires an unsafe function or block
+}         //^^ error: this operation is unsafe and requires an unsafe function or block
 "#,
         )
     }
@@ -48,9 +48,9 @@ unsafe fn unsafe_fn() {
 
 fn main() {
     unsafe_fn();
-  //^^^^^^^^^^^ this operation is unsafe and requires an unsafe function or block
+  //^^^^^^^^^^^ error: this operation is unsafe and requires an unsafe function or block
     HasUnsafe.unsafe_fn();
-  //^^^^^^^^^^^^^^^^^^^^^ this operation is unsafe and requires an unsafe function or block
+  //^^^^^^^^^^^^^^^^^^^^^ error: this operation is unsafe and requires an unsafe function or block
     unsafe {
         unsafe_fn();
         HasUnsafe.unsafe_fn();
@@ -72,7 +72,7 @@ static mut STATIC_MUT: Ty = Ty { a: 0 };
 
 fn main() {
     let x = STATIC_MUT.a;
-          //^^^^^^^^^^ this operation is unsafe and requires an unsafe function or block
+          //^^^^^^^^^^ error: this operation is unsafe and requires an unsafe function or block
     unsafe {
         let x = STATIC_MUT.a;
     }
@@ -93,7 +93,7 @@ extern "rust-intrinsic" {
 fn main() {
     let _ = bitreverse(12);
     let _ = floorf32(12.0);
-          //^^^^^^^^^^^^^^ this operation is unsafe and requires an unsafe function or block
+          //^^^^^^^^^^^^^^ error: this operation is unsafe and requires an unsafe function or block
 }
 "#,
         );
diff --git a/crates/ide_diagnostics/src/handlers/no_such_field.rs b/crates/ide_diagnostics/src/handlers/no_such_field.rs
index e4cc8a840..92e8867f4 100644
--- a/crates/ide_diagnostics/src/handlers/no_such_field.rs
+++ b/crates/ide_diagnostics/src/handlers/no_such_field.rs
@@ -119,11 +119,11 @@ struct S { foo: i32, bar: () }
 impl S {
     fn new() -> S {
         S {
-      //^ Missing structure fields:
+      //^ 💡 error: missing structure fields:
       //|    - bar
             foo: 92,
             baz: 62,
-          //^^^^^^^ no such field
+          //^^^^^^^ 💡 error: no such field
         }
     }
 }
diff --git a/crates/ide_diagnostics/src/handlers/remove_this_semicolon.rs b/crates/ide_diagnostics/src/handlers/remove_this_semicolon.rs
index b52e4dc84..4e639f214 100644
--- a/crates/ide_diagnostics/src/handlers/remove_this_semicolon.rs
+++ b/crates/ide_diagnostics/src/handlers/remove_this_semicolon.rs
@@ -49,7 +49,7 @@ mod tests {
         check_diagnostics(
             r#"
 fn test() -> i32 { 123; }
-                 //^^^ remove this semicolon
+                 //^^^ 💡 error: remove this semicolon
 "#,
         );
     }
diff --git a/crates/ide_diagnostics/src/handlers/replace_filter_map_next_with_find_map.rs b/crates/ide_diagnostics/src/handlers/replace_filter_map_next_with_find_map.rs
index 10d5da15d..cd87a10bb 100644
--- a/crates/ide_diagnostics/src/handlers/replace_filter_map_next_with_find_map.rs
+++ b/crates/ide_diagnostics/src/handlers/replace_filter_map_next_with_find_map.rs
@@ -91,8 +91,8 @@ pub mod iter {
         check_diagnostics(
             r#"
     fn foo() {
-        let m = [1, 2, 3].iter().filter_map(|x| if *x == 2 { Some (4) } else { None }).next();
-    }         //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ replace filter_map(..).next() with find_map(..)
+        let m = [1, 2, 3].iter().filter_map(|x| Some(92)).next();
+    }         //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 💡 weak: replace filter_map(..).next() with find_map(..)
 "#,
         );
     }
@@ -104,7 +104,7 @@ pub mod iter {
 fn foo() {
     let m = [1, 2, 3]
         .iter()
-        .filter_map(|x| if *x == 2 { Some (4) } else { None })
+        .filter_map(|x| Some(92))
         .len();
 }
 "#,
@@ -118,7 +118,7 @@ fn foo() {
 fn foo() {
     let m = [1, 2, 3]
         .iter()
-        .filter_map(|x| if *x == 2 { Some (4) } else { None })
+        .filter_map(|x| Some(92))
         .map(|x| x + 2)
         .len();
 }
@@ -133,7 +133,7 @@ fn foo() {
 fn foo() {
     let m = [1, 2, 3]
         .iter()
-        .filter_map(|x| if *x == 2 { Some (4) } else { None });
+        .filter_map(|x| Some(92));
     let n = m.next();
 }
 "#,
@@ -148,7 +148,7 @@ fn foo() {
 use core::iter::Iterator;
 use core::option::Option::{self, Some, None};
 fn foo() {
-    let m = [1, 2, 3].iter().$0filter_map(|x| if *x == 2 { Some (4) } else { None }).next();
+    let m = [1, 2, 3].iter().$0filter_map(|x| Some(92)).next();
 }
 //- /core/lib.rs crate:core
 pub mod option {
@@ -171,7 +171,7 @@ pub mod iter {
 use core::iter::Iterator;
 use core::option::Option::{self, Some, None};
 fn foo() {
-    let m = [1, 2, 3].iter().find_map(|x| if *x == 2 { Some (4) } else { None });
+    let m = [1, 2, 3].iter().find_map(|x| Some(92));
 }
 "#,
         )
diff --git a/crates/ide_diagnostics/src/handlers/unlinked_file.rs b/crates/ide_diagnostics/src/handlers/unlinked_file.rs
index 8921ddde2..8e601fa48 100644
--- a/crates/ide_diagnostics/src/handlers/unlinked_file.rs
+++ b/crates/ide_diagnostics/src/handlers/unlinked_file.rs
@@ -14,32 +14,29 @@ use text_edit::TextEdit;
 
 use crate::{fix, Assist, Diagnostic, DiagnosticsContext};
 
-#[derive(Debug)]
-pub(crate) struct UnlinkedFile {
-    pub(crate) file: FileId,
-}
-
 // Diagnostic: unlinked-file
 //
 // This diagnostic is shown for files that are not included in any crate, or files that are part of
 // crates rust-analyzer failed to discover. The file will not have IDE features available.
-pub(crate) fn unlinked_file(ctx: &DiagnosticsContext, d: &UnlinkedFile) -> Diagnostic {
+pub(crate) fn unlinked_file(ctx: &DiagnosticsContext, acc: &mut Vec<Diagnostic>, file_id: FileId) {
     // Limit diagnostic to the first few characters in the file. This matches how VS Code
     // renders it with the full span, but on other editors, and is less invasive.
-    let range = ctx.sema.db.parse(d.file).syntax_node().text_range();
+    let range = ctx.sema.db.parse(file_id).syntax_node().text_range();
     // FIXME: This is wrong if one of the first three characters is not ascii: `//Ы`.
     let range = range.intersect(TextRange::up_to(TextSize::of("..."))).unwrap_or(range);
 
-    Diagnostic::new("unlinked-file", "file not included in module tree", range)
-        .with_fixes(fixes(ctx, d))
+    acc.push(
+        Diagnostic::new("unlinked-file", "file not included in module tree", range)
+            .with_fixes(fixes(ctx, file_id)),
+    );
 }
 
-fn fixes(ctx: &DiagnosticsContext, d: &UnlinkedFile) -> Option<Vec<Assist>> {
+fn fixes(ctx: &DiagnosticsContext, file_id: FileId) -> Option<Vec<Assist>> {
     // If there's an existing module that could add `mod` or `pub mod` items to include the unlinked file,
     // suggest that as a fix.
 
-    let source_root = ctx.sema.db.source_root(ctx.sema.db.file_source_root(d.file));
-    let our_path = source_root.path_for_file(&d.file)?;
+    let source_root = ctx.sema.db.source_root(ctx.sema.db.file_source_root(file_id));
+    let our_path = source_root.path_for_file(&file_id)?;
     let module_name = our_path.name_and_extension()?.0;
 
     // Candidates to look for:
@@ -68,7 +65,7 @@ fn fixes(ctx: &DiagnosticsContext, d: &UnlinkedFile) -> Option<Vec<Assist>> {
                     }
 
                     if module.origin.file_id() == Some(*parent_id) {
-                        return make_fixes(ctx.sema.db, *parent_id, module_name, d.file);
+                        return make_fixes(ctx.sema.db, *parent_id, module_name, file_id);
                     }
                 }
             }
diff --git a/crates/ide_diagnostics/src/handlers/unresolved_extern_crate.rs b/crates/ide_diagnostics/src/handlers/unresolved_extern_crate.rs
index f5313cc0c..74e4a69c6 100644
--- a/crates/ide_diagnostics/src/handlers/unresolved_extern_crate.rs
+++ b/crates/ide_diagnostics/src/handlers/unresolved_extern_crate.rs
@@ -25,7 +25,7 @@ mod tests {
 //- /main.rs crate:main deps:core
 extern crate core;
   extern crate doesnotexist;
-//^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+//^^^^^^^^^^^^^^^^^^^^^^^^^^ error: unresolved extern crate
 //- /lib.rs crate:core
 "#,
         );
@@ -38,7 +38,7 @@ extern crate core;
             r#"
 //- /lib.rs
   extern crate doesnotexist;
-//^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+//^^^^^^^^^^^^^^^^^^^^^^^^^^ error: unresolved extern crate
 // Should not error.
 extern crate self as foo;
 struct Foo;
diff --git a/crates/ide_diagnostics/src/handlers/unresolved_import.rs b/crates/ide_diagnostics/src/handlers/unresolved_import.rs
index f30051c12..e52a88459 100644
--- a/crates/ide_diagnostics/src/handlers/unresolved_import.rs
+++ b/crates/ide_diagnostics/src/handlers/unresolved_import.rs
@@ -30,7 +30,7 @@ mod tests {
             r#"
 use does_exist;
 use does_not_exist;
-  //^^^^^^^^^^^^^^ unresolved import
+  //^^^^^^^^^^^^^^ error: unresolved import
 
 mod does_exist {}
 "#,
@@ -43,18 +43,18 @@ mod does_exist {}
         check_diagnostics(
             r#"
 use does_exist::{Exists, DoesntExist};
-                       //^^^^^^^^^^^ unresolved import
+                       //^^^^^^^^^^^ error: unresolved import
 
 use {does_not_exist::*, does_exist};
-   //^^^^^^^^^^^^^^^^^ unresolved import
+   //^^^^^^^^^^^^^^^^^ error: unresolved import
 
 use does_not_exist::{
     a,
-  //^ unresolved import
+  //^ error: unresolved import
     b,
-  //^ unresolved import
+  //^ error: unresolved import
     c,
-  //^ unresolved import
+  //^ error: unresolved import
 };
 
 mod does_exist {
@@ -71,18 +71,18 @@ mod does_exist {
 //- /main.rs crate:main
 mod a {
     extern crate doesnotexist;
-  //^^^^^^^^^^^^^^^^^^^^^^^^^^ unresolved extern crate
+  //^^^^^^^^^^^^^^^^^^^^^^^^^^ error: unresolved extern crate
 
     // Should not error, since we already errored for the missing crate.
     use doesnotexist::{self, bla, *};
 
     use crate::doesnotexist;
-      //^^^^^^^^^^^^^^^^^^^ unresolved import
+      //^^^^^^^^^^^^^^^^^^^ error: unresolved import
 }
 
 mod m {
     use super::doesnotexist;
-      //^^^^^^^^^^^^^^^^^^^ unresolved import
+      //^^^^^^^^^^^^^^^^^^^ error: unresolved import
 }
 "#,
         );
diff --git a/crates/ide_diagnostics/src/handlers/unresolved_macro_call.rs b/crates/ide_diagnostics/src/handlers/unresolved_macro_call.rs
index 4c3c1c19a..f0f7725db 100644
--- a/crates/ide_diagnostics/src/handlers/unresolved_macro_call.rs
+++ b/crates/ide_diagnostics/src/handlers/unresolved_macro_call.rs
@@ -40,7 +40,7 @@ mod tests {
             r#"
 fn f() {
     m!();
-} //^ unresolved macro `m!`
+} //^ error: unresolved macro `m!`
 
 "#,
         );
@@ -51,7 +51,7 @@ fn f() {
         check_diagnostics(
             r#"
 foo::bar!(92);
-   //^^^ unresolved macro `foo::bar!`
+   //^^^ error: unresolved macro `foo::bar!`
 "#,
         );
     }
@@ -63,7 +63,7 @@ foo::bar!(92);
 macro_rules! m { () => {} }
 
 m!(); m2!();
-    //^^ unresolved macro `self::m2!`
+    //^^ error: unresolved macro `self::m2!`
 "#,
         );
     }
@@ -77,7 +77,7 @@ mod mac {
 macro_rules! m { () => {} } }
 
 self::m!(); self::m2!();
-                //^^ unresolved macro `self::m2!`
+                //^^ error: unresolved macro `self::m2!`
 "#,
         );
     }
diff --git a/crates/ide_diagnostics/src/handlers/unresolved_module.rs b/crates/ide_diagnostics/src/handlers/unresolved_module.rs
index 17166a0c6..61fc43604 100644
--- a/crates/ide_diagnostics/src/handlers/unresolved_module.rs
+++ b/crates/ide_diagnostics/src/handlers/unresolved_module.rs
@@ -50,7 +50,7 @@ mod tests {
 //- /lib.rs
 mod foo;
   mod bar;
-//^^^^^^^^ unresolved module
+//^^^^^^^^ 💡 error: unresolved module
 mod baz {}
 //- /foo.rs
 "#,
diff --git a/crates/ide_diagnostics/src/handlers/useless_braces.rs b/crates/ide_diagnostics/src/handlers/useless_braces.rs
new file mode 100644
index 000000000..8b9330e04
--- /dev/null
+++ b/crates/ide_diagnostics/src/handlers/useless_braces.rs
@@ -0,0 +1,148 @@
+use ide_db::{base_db::FileId, source_change::SourceChange};
+use itertools::Itertools;
+use syntax::{ast, AstNode, SyntaxNode, TextRange};
+use text_edit::TextEdit;
+
+use crate::{fix, Diagnostic, Severity};
+
+// Diagnostic: unnecessary-braces
+//
+// Diagnostic for unnecessary braces in `use` items.
+pub(crate) fn useless_braces(
+    acc: &mut Vec<Diagnostic>,
+    file_id: FileId,
+    node: &SyntaxNode,
+) -> Option<()> {
+    let use_tree_list = ast::UseTreeList::cast(node.clone())?;
+    if let Some((single_use_tree,)) = use_tree_list.use_trees().collect_tuple() {
+        // If there is a comment inside the bracketed `use`,
+        // assume it is a commented out module path and don't show diagnostic.
+        if use_tree_list.has_inner_comment() {
+            return Some(());
+        }
+
+        let use_range = use_tree_list.syntax().text_range();
+        let edit = remove_braces(&single_use_tree).unwrap_or_else(|| {
+            let to_replace = single_use_tree.syntax().text().to_string();
+            let mut edit_builder = TextEdit::builder();
+            edit_builder.delete(use_range);
+            edit_builder.insert(use_range.start(), to_replace);
+            edit_builder.finish()
+        });
+
+        acc.push(
+            Diagnostic::new(
+                "unnecessary-braces",
+                "Unnecessary braces in use statement".to_string(),
+                use_range,
+            )
+            .severity(Severity::WeakWarning)
+            .with_fixes(Some(vec![fix(
+                "remove_braces",
+                "Remove unnecessary braces",
+                SourceChange::from_text_edit(file_id, edit),
+                use_range,
+            )])),
+        );
+    }
+
+    Some(())
+}
+
+fn remove_braces(single_use_tree: &ast::UseTree) -> Option<TextEdit> {
+    let use_tree_list_node = single_use_tree.syntax().parent()?;
+    if single_use_tree.path()?.segment()?.self_token().is_some() {
+        let start = use_tree_list_node.prev_sibling_or_token()?.text_range().start();
+        let end = use_tree_list_node.text_range().end();
+        return Some(TextEdit::delete(TextRange::new(start, end)));
+    }
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_diagnostics, check_fix};
+
+    #[test]
+    fn test_check_unnecessary_braces_in_use_statement() {
+        check_diagnostics(
+            r#"
+use a;
+use a::{c, d::e};
+
+mod a {
+    mod c {}
+    mod d {
+        mod e {}
+    }
+}
+"#,
+        );
+        check_diagnostics(
+            r#"
+use a;
+use a::{
+    c,
+    // d::e
+};
+
+mod a {
+    mod c {}
+    mod d {
+        mod e {}
+    }
+}
+"#,
+        );
+        check_fix(
+            r#"
+mod b {}
+use {$0b};
+"#,
+            r#"
+mod b {}
+use b;
+"#,
+        );
+        check_fix(
+            r#"
+mod b {}
+use {b$0};
+"#,
+            r#"
+mod b {}
+use b;
+"#,
+        );
+        check_fix(
+            r#"
+mod a { mod c {} }
+use a::{c$0};
+"#,
+            r#"
+mod a { mod c {} }
+use a::c;
+"#,
+        );
+        check_fix(
+            r#"
+mod a {}
+use a::{self$0};
+"#,
+            r#"
+mod a {}
+use a;
+"#,
+        );
+        check_fix(
+            r#"
+mod a { mod c {} mod d { mod e {} } }
+use a::{c, d::{e$0}};
+"#,
+            r#"
+mod a { mod c {} mod d { mod e {} } }
+use a::{c, d::e};
+"#,
+        );
+    }
+}
diff --git a/crates/ide_diagnostics/src/lib.rs b/crates/ide_diagnostics/src/lib.rs
index 88037be5a..6ad1b4373 100644
--- a/crates/ide_diagnostics/src/lib.rs
+++ b/crates/ide_diagnostics/src/lib.rs
@@ -37,15 +37,17 @@ mod handlers {
     pub(crate) mod remove_this_semicolon;
     pub(crate) mod replace_filter_map_next_with_find_map;
     pub(crate) mod unimplemented_builtin_macro;
-    pub(crate) mod unlinked_file;
     pub(crate) mod unresolved_extern_crate;
     pub(crate) mod unresolved_import;
     pub(crate) mod unresolved_macro_call;
     pub(crate) mod unresolved_module;
     pub(crate) mod unresolved_proc_macro;
-}
 
-mod field_shorthand;
+    // The handlers bellow are unusual, the implement the diagnostics as well.
+    pub(crate) mod field_shorthand;
+    pub(crate) mod useless_braces;
+    pub(crate) mod unlinked_file;
+}
 
 use hir::{diagnostics::AnyDiagnostic, Semantics};
 use ide_db::{
@@ -55,15 +57,8 @@ use ide_db::{
     source_change::SourceChange,
     RootDatabase,
 };
-use itertools::Itertools;
 use rustc_hash::FxHashSet;
-use syntax::{
-    ast::{self, AstNode},
-    SyntaxNode, TextRange,
-};
-use text_edit::TextEdit;
-
-use crate::handlers::unlinked_file::UnlinkedFile;
+use syntax::{ast::AstNode, TextRange};
 
 #[derive(Copy, Clone, Debug, PartialEq)]
 pub struct DiagnosticCode(pub &'static str);
@@ -123,6 +118,8 @@ impl Diagnostic {
 #[derive(Debug, Copy, Clone)]
 pub enum Severity {
     Error,
+    // We don't actually emit this one yet, but we should at some point.
+    // Warning,
     WeakWarning,
 }
 
@@ -157,21 +154,20 @@ pub fn diagnostics(
     );
 
     for node in parse.tree().syntax().descendants() {
-        check_unnecessary_braces_in_use_statement(&mut res, file_id, &node);
-        field_shorthand::check(&mut res, file_id, &node);
+        handlers::useless_braces::useless_braces(&mut res, file_id, &node);
+        handlers::field_shorthand::field_shorthand(&mut res, file_id, &node);
     }
 
-    let mut diags = Vec::new();
     let module = sema.to_module_def(file_id);
-    if let Some(m) = module {
-        m.diagnostics(db, &mut diags)
-    }
 
     let ctx = DiagnosticsContext { config, sema, resolve };
     if module.is_none() {
-        let d = UnlinkedFile { file: file_id };
-        let d = handlers::unlinked_file::unlinked_file(&ctx, &d);
-        res.push(d)
+        handlers::unlinked_file::unlinked_file(&ctx, &mut res, file_id);
+    }
+
+    let mut diags = Vec::new();
+    if let Some(m) = module {
+        m.diagnostics(db, &mut diags)
     }
 
     for diag in diags {
@@ -211,61 +207,6 @@ pub fn diagnostics(
     res
 }
 
-fn check_unnecessary_braces_in_use_statement(
-    acc: &mut Vec<Diagnostic>,
-    file_id: FileId,
-    node: &SyntaxNode,
-) -> Option<()> {
-    let use_tree_list = ast::UseTreeList::cast(node.clone())?;
-    if let Some((single_use_tree,)) = use_tree_list.use_trees().collect_tuple() {
-        // If there is a comment inside the bracketed `use`,
-        // assume it is a commented out module path and don't show diagnostic.
-        if use_tree_list.has_inner_comment() {
-            return Some(());
-        }
-
-        let use_range = use_tree_list.syntax().text_range();
-        let edit =
-            text_edit_for_remove_unnecessary_braces_with_self_in_use_statement(&single_use_tree)
-                .unwrap_or_else(|| {
-                    let to_replace = single_use_tree.syntax().text().to_string();
-                    let mut edit_builder = TextEdit::builder();
-                    edit_builder.delete(use_range);
-                    edit_builder.insert(use_range.start(), to_replace);
-                    edit_builder.finish()
-                });
-
-        acc.push(
-            Diagnostic::new(
-                "unnecessary-braces",
-                "Unnecessary braces in use statement".to_string(),
-                use_range,
-            )
-            .severity(Severity::WeakWarning)
-            .with_fixes(Some(vec![fix(
-                "remove_braces",
-                "Remove unnecessary braces",
-                SourceChange::from_text_edit(file_id, edit),
-                use_range,
-            )])),
-        );
-    }
-
-    Some(())
-}
-
-fn text_edit_for_remove_unnecessary_braces_with_self_in_use_statement(
-    single_use_tree: &ast::UseTree,
-) -> Option<TextEdit> {
-    let use_tree_list_node = single_use_tree.syntax().parent()?;
-    if single_use_tree.path()?.segment()?.self_token().is_some() {
-        let start = use_tree_list_node.prev_sibling_or_token()?.text_range().start();
-        let end = use_tree_list_node.text_range().end();
-        return Some(TextEdit::delete(TextRange::new(start, end)));
-    }
-    None
-}
-
 fn fix(id: &'static str, label: &str, source_change: SourceChange, target: TextRange) -> Assist {
     let mut res = unresolved_fix(id, label, target);
     res.source_change = Some(source_change);
@@ -294,7 +235,7 @@ mod tests {
     use stdx::trim_indent;
     use test_utils::{assert_eq_text, extract_annotations};
 
-    use crate::DiagnosticsConfig;
+    use crate::{DiagnosticsConfig, Severity};
 
     /// Takes a multi-file input fixture with annotated cursor positions,
     /// and checks that:
@@ -390,97 +331,29 @@ mod tests {
                 super::diagnostics(&db, &config, &AssistResolveStrategy::All, file_id);
 
             let expected = extract_annotations(&*db.file_text(file_id));
-            let mut actual =
-                diagnostics.into_iter().map(|d| (d.range, d.message)).collect::<Vec<_>>();
+            let mut actual = diagnostics
+                .into_iter()
+                .map(|d| {
+                    let mut annotation = String::new();
+                    if let Some(fixes) = &d.fixes {
+                        assert!(!fixes.is_empty());
+                        annotation.push_str("💡 ")
+                    }
+                    annotation.push_str(match d.severity {
+                        Severity::Error => "error",
+                        Severity::WeakWarning => "weak",
+                    });
+                    annotation.push_str(": ");
+                    annotation.push_str(&d.message);
+                    (d.range, annotation)
+                })
+                .collect::<Vec<_>>();
             actual.sort_by_key(|(range, _)| range.start());
             assert_eq!(expected, actual);
         }
     }
 
     #[test]
-    fn test_check_unnecessary_braces_in_use_statement() {
-        check_diagnostics(
-            r#"
-use a;
-use a::{c, d::e};
-
-mod a {
-    mod c {}
-    mod d {
-        mod e {}
-    }
-}
-"#,
-        );
-        check_diagnostics(
-            r#"
-use a;
-use a::{
-    c,
-    // d::e
-};
-
-mod a {
-    mod c {}
-    mod d {
-        mod e {}
-    }
-}
-"#,
-        );
-        check_fix(
-            r"
-            mod b {}
-            use {$0b};
-            ",
-            r"
-            mod b {}
-            use b;
-            ",
-        );
-        check_fix(
-            r"
-            mod b {}
-            use {b$0};
-            ",
-            r"
-            mod b {}
-            use b;
-            ",
-        );
-        check_fix(
-            r"
-            mod a { mod c {} }
-            use a::{c$0};
-            ",
-            r"
-            mod a { mod c {} }
-            use a::c;
-            ",
-        );
-        check_fix(
-            r"
-            mod a {}
-            use a::{self$0};
-            ",
-            r"
-            mod a {}
-            use a;
-            ",
-        );
-        check_fix(
-            r"
-            mod a { mod c {} mod d { mod e {} } }
-            use a::{c, d::{e$0}};
-            ",
-            r"
-            mod a { mod c {} mod d { mod e {} } }
-            use a::{c, d::e};
-            ",
-        );
-    }
-
-    #[test]
     fn test_disabled_diagnostics() {
         let mut config = DiagnosticsConfig::default();
         config.disabled.insert("unresolved-module".into());
@@ -498,33 +371,4 @@ mod a {
         );
         assert!(!diagnostics.is_empty());
     }
-
-    #[test]
-    fn import_extern_crate_clash_with_inner_item() {
-        // This is more of a resolver test, but doesn't really work with the hir_def testsuite.
-
-        check_diagnostics(
-            r#"
-//- /lib.rs crate:lib deps:jwt
-mod permissions;
-
-use permissions::jwt;
-
-fn f() {
-    fn inner() {}
-    jwt::Claims {}; // should resolve to the local one with 0 fields, and not get a diagnostic
-}
-
-//- /permissions.rs
-pub mod jwt  {
-    pub struct Claims {}
-}
-
-//- /jwt/lib.rs crate:jwt
-pub struct Claims {
-    field: u8,
-}
-        "#,
-        );
-    }
 }