Improve make::struct_ field_list whitespace

Example
---
**Before this PR**:

```rust
struct Variant{
    field: u32
}
```

**After this PR**:

```rust
struct Variant {
    field: u32
}
```

crates/ide-assists/src/handlers/extract_struct_from_enum_variant.rs

@@ -478,7 +478,7 @@ macro_rules! foo {
     };
 }
 
-struct TheVariant{ the_field: u8 }
+struct TheVariant { the_field: u8 }
 
 enum TheEnum {
     TheVariant(TheVariant),
@@ -502,7 +502,7 @@ enum Foo {
 }
 "#,
             r#"
-struct Bar{ node: Box<Foo> }
+struct Bar { node: Box<Foo> }
 
 enum Foo {
     Bar(Bar),
@@ -519,7 +519,7 @@ enum Foo {
 }
 "#,
             r#"
-struct Bar{ node: Box<Foo>, a: Arc<Box<Foo>> }
+struct Bar { node: Box<Foo>, a: Arc<Box<Foo>> }
 
 enum Foo {
     Bar(Bar),
@@ -560,7 +560,7 @@ enum A { One(One) }"#,
         check_assist(
             extract_struct_from_enum_variant,
             "enum A { $0One { foo: u32, bar: u32 } }",
-            r#"struct One{ foo: u32, bar: u32 }
+            r#"struct One { foo: u32, bar: u32 }
 
 enum A { One(One) }"#,
         );
@@ -571,7 +571,7 @@ enum A { One(One) }"#,
         check_assist(
             extract_struct_from_enum_variant,
             "enum A { $0One { foo: u32 } }",
-            r#"struct One{ foo: u32 }
+            r#"struct One { foo: u32 }
 
 enum A { One(One) }"#,
         );
@@ -582,7 +582,7 @@ enum A { One(One) }"#,
         check_assist(
             extract_struct_from_enum_variant,
             r"enum En<T> { Var { a: T$0 } }",
-            r#"struct Var<T>{ a: T }
+            r#"struct Var<T> { a: T }
 
 enum En<T> { Var(Var<T>) }"#,
         );
@@ -599,7 +599,7 @@ enum Enum { Variant{ field: u32$0 } }"#,
             r#"
 #[derive(Debug)]
 #[derive(Clone)]
-struct Variant{ field: u32 }
+struct Variant { field: u32 }
 
 #[derive(Debug)]
 #[derive(Clone)]
@@ -618,7 +618,7 @@ enum Enum {
     }
 }"#,
             r#"
-struct Variant{
+struct Variant {
     field: u32
 }
 
@@ -642,7 +642,7 @@ mod indenting {
 }"#,
             r#"
 mod indenting {
-    struct Variant{
+    struct Variant {
         field: u32
     }
 
@@ -668,7 +668,7 @@ enum A {
     }
 }"#,
             r#"
-struct One{
+struct One {
     // leading comment
     /// doc comment
     #[an_attr]
@@ -700,7 +700,7 @@ enum A {
     }
 }"#,
             r#"
-struct One{
+struct One {
     // comment
     /// doc
     #[attr]
@@ -747,7 +747,7 @@ enum A {
 /* comment */
 // other
 /// comment
-struct One{
+struct One {
     a: u32
 }
 
@@ -789,7 +789,7 @@ enum A {
             extract_struct_from_enum_variant,
             "enum A { $0One{ a: u32, pub(crate) b: u32, pub(super) c: u32, d: u32 } }",
             r#"
-struct One{ a: u32, pub(crate) b: u32, pub(super) c: u32, d: u32 }
+struct One { a: u32, pub(crate) b: u32, pub(super) c: u32, d: u32 }
 
 enum A { One(One) }"#,
         );
@@ -850,7 +850,7 @@ pub enum A { One(One) }"#,
             extract_struct_from_enum_variant,
             "pub(in something) enum A { $0One{ a: u32, b: u32 } }",
             r#"
-pub(in something) struct One{ pub(in something) a: u32, pub(in something) b: u32 }
+pub(in something) struct One { pub(in something) a: u32, pub(in something) b: u32 }
 
 pub(in something) enum A { One(One) }"#,
         );
@@ -862,7 +862,7 @@ pub(in something) enum A { One(One) }"#,
             extract_struct_from_enum_variant,
             "pub(crate) enum A { $0One{ a: u32, b: u32, c: u32 } }",
             r#"
-pub(crate) struct One{ pub(crate) a: u32, pub(crate) b: u32, pub(crate) c: u32 }
+pub(crate) struct One { pub(crate) a: u32, pub(crate) b: u32, pub(crate) c: u32 }
 
 pub(crate) enum A { One(One) }"#,
         );
@@ -933,7 +933,7 @@ fn f() {
 }
 "#,
             r#"
-struct V{ i: i32, j: i32 }
+struct V { i: i32, j: i32 }
 
 enum E {
     V(V)
@@ -1027,7 +1027,7 @@ fn f() {
 "#,
             r#"
 //- /main.rs
-struct V{ i: i32, j: i32 }
+struct V { i: i32, j: i32 }
 
 enum E {
     V(V)
@@ -1057,7 +1057,7 @@ fn foo() {
 }
 "#,
             r#"
-struct One{ a: u32, b: u32 }
+struct One { a: u32, b: u32 }
 
 enum A { One(One) }
 
@@ -1114,7 +1114,7 @@ enum X<'a, 'b, 'x> {
 }
 "#,
             r#"
-struct A<'a, 'x>{ a: &'a &'x mut () }
+struct A<'a, 'x> { a: &'a &'x mut () }
 
 enum X<'a, 'b, 'x> {
     A(A<'a, 'x>),
@@ -1136,7 +1136,7 @@ enum X<'b, T, V, const C: usize> {
 }
 "#,
             r#"
-struct A<'b, T, const C: usize>{ a: T, b: X<'b>, c: [u8; C] }
+struct A<'b, T, const C: usize> { a: T, b: X<'b>, c: [u8; C] }
 
 enum X<'b, T, V, const C: usize> {
     A(A<'b, T, C>),
@@ -1158,7 +1158,7 @@ enum X<'a, 'b> {
 }
 "#,
             r#"
-struct C{ c: () }
+struct C { c: () }
 
 enum X<'a, 'b> {
     A { a: &'a () },
@@ -1180,7 +1180,7 @@ enum En<T: TraitT, V: TraitV> {
 }
 "#,
             r#"
-struct A<T: TraitT>{ a: T }
+struct A<T: TraitT> { a: T }
 
 enum En<T: TraitT, V: TraitV> {
     A(A<T>),

crates/ide-diagnostics/src/handlers/json_is_not_rust.rs

@@ -233,7 +233,7 @@ mod tests {
             }
 
             #[derive(Serialize)]
-            struct Root1{ bar: f64, bay: i64, baz: (), r#box: bool, foo: String }
+            struct Root1 { bar: f64, bay: i64, baz: (), r#box: bool, foo: String }
 
             "#,
         );
@@ -252,9 +252,9 @@ mod tests {
             }
             "#,
             r#"
-            struct Value1{  }
+            struct Value1 {  }
-            struct Bar1{ kind: String, value: Value1 }
+            struct Bar1 { kind: String, value: Value1 }
-            struct Root1{ bar: Bar1, foo: String }
+            struct Root1 { bar: Bar1, foo: String }
 
             "#,
         );
@@ -284,12 +284,12 @@ mod tests {
             }
             "#,
             r#"
-            struct Address1{ house: i64, street: String }
+            struct Address1 { house: i64, street: String }
-            struct User1{ address: Address1, email: String }
+            struct User1 { address: Address1, email: String }
-            struct AnotherUser1{ user: User1 }
+            struct AnotherUser1 { user: User1 }
-            struct Address2{ house: i64, street: String }
+            struct Address2 { house: i64, street: String }
-            struct User2{ address: Address2, email: String }
+            struct User2 { address: Address2, email: String }
-            struct Root1{ another_user: AnotherUser1, user: User2 }
+            struct Root1 { another_user: AnotherUser1, user: User2 }
 
             "#,
         );
@@ -326,9 +326,9 @@ mod tests {
             use serde::Deserialize;
 
             #[derive(Serialize, Deserialize)]
-            struct OfObject1{ x: i64, y: i64 }
+            struct OfObject1 { x: i64, y: i64 }
             #[derive(Serialize, Deserialize)]
-            struct Root1{ empty: Vec<_>, nested: Vec<Vec<Vec<i64>>>, of_object: Vec<OfObject1>, of_string: Vec<String> }
+            struct Root1 { empty: Vec<_>, nested: Vec<Vec<Vec<i64>>>, of_object: Vec<OfObject1>, of_string: Vec<String> }
 
             "#,
         );

crates/syntax/src/ast/make.rs

@@ -1244,14 +1244,17 @@ pub fn struct_(
     generic_param_list: Option<ast::GenericParamList>,
     field_list: ast::FieldList,
 ) -> ast::Struct {
-    let semicolon = if matches!(field_list, ast::FieldList::TupleFieldList(_)) { ";" } else { "" };
+    let (semicolon, ws) =
+        if matches!(field_list, ast::FieldList::TupleFieldList(_)) { (";", "") } else { ("", " ") };
     let type_params = generic_param_list.map_or_else(String::new, |it| it.to_string());
     let visibility = match visibility {
         None => String::new(),
         Some(it) => format!("{it} "),
     };
 
-    ast_from_text(&format!("{visibility}struct {strukt_name}{type_params}{field_list}{semicolon}",))
+    ast_from_text(&format!(
+        "{visibility}struct {strukt_name}{type_params}{ws}{field_list}{semicolon}"
+    ))
 }
 
 pub fn enum_(