4 files changed, 218 insertions, 2 deletions

diff --git a/crates/ra_assists/src/handlers/reorder_fields.rs b/crates/ra_assists/src/handlers/reorder_fields.rs
new file mode 100644
index 000000000..c17c1288c
--- /dev/null
+++ b/crates/ra_assists/src/handlers/reorder_fields.rs
@@ -0,0 +1,207 @@
+use std::collections::HashMap;
+
+use itertools::Itertools;
+
+use hir::{Adt, ModuleDef, PathResolution, Semantics, Struct};
+use ra_ide_db::RootDatabase;
+use ra_syntax::ast::{Name, Pat};
+use ra_syntax::{
+    ast,
+    ast::{Path, RecordField, RecordLit, RecordPat},
+    AstNode,
+};
+
+use crate::{
+    assist_ctx::{Assist, AssistCtx},
+    AssistId,
+};
+
+pub(crate) fn reorder_fields(ctx: AssistCtx) -> Option<Assist> {
+    reorder_struct(ctx.clone()).or_else(|| reorder_struct_pat(ctx))
+}
+
+fn reorder_struct(ctx: AssistCtx) -> Option<Assist> {
+    let record: RecordLit = ctx.find_node_at_offset()?;
+    reorder(ctx, &record, &record.path()?, field_name)
+}
+
+fn field_name(r: &RecordField) -> String {
+    r.name_ref()
+        .map(|name| name.syntax().text())
+        .unwrap_or_else(|| r.expr().unwrap().syntax().text())
+        .to_string()
+}
+
+fn reorder_struct_pat(ctx: AssistCtx) -> Option<Assist> {
+    let record: RecordPat = ctx.find_node_at_offset()?;
+    reorder(ctx, &record, &record.path()?, field_pat_name)
+}
+
+fn field_pat_name(field: &Pat) -> String {
+    field.syntax().children().find_map(Name::cast).map(|n| n.to_string()).unwrap_or_default()
+}
+
+fn reorder<R: AstNode, F: AstNode + Eq + Clone>(
+    ctx: AssistCtx,
+    record: &R,
+    path: &Path,
+    field_name: fn(&F) -> String,
+) -> Option<Assist> {
+    let ranks = compute_fields_ranks(path, &ctx)?;
+    let fields: Vec<F> = get_fields(record);
+    let sorted_fields: Vec<F> =
+        sort_by_rank(&fields, |f| *ranks.get(&field_name(f)).unwrap_or(&usize::max_value()));
+
+    if sorted_fields == fields {
+        return None;
+    }
+
+    ctx.add_assist(AssistId("reorder_fields"), "Reorder record fields", |edit| {
+        for (old, new) in fields.into_iter().zip(sorted_fields) {
+            edit.replace_ast(old, new);
+        }
+        edit.target(record.syntax().text_range())
+    })
+}
+
+fn get_fields<R: AstNode, F: AstNode>(record: &R) -> Vec<F> {
+    record.syntax().children().flat_map(|n1| n1.children()).filter_map(|n3| F::cast(n3)).collect()
+}
+
+fn sort_by_rank<F: AstNode + Clone>(fields: &[F], get_rank: impl FnMut(&F) -> usize) -> Vec<F> {
+    fields.iter().cloned().sorted_by_key(get_rank).collect()
+}
+
+fn struct_definition(path: &ast::Path, sema: &Semantics<RootDatabase>) -> Option<Struct> {
+    match sema.resolve_path(path) {
+        Some(PathResolution::Def(ModuleDef::Adt(Adt::Struct(s)))) => Some(s),
+        _ => None,
+    }
+}
+
+fn compute_fields_ranks(path: &Path, ctx: &AssistCtx) -> Option<HashMap<String, usize>> {
+    Some(
+        struct_definition(path, ctx.sema)?
+            .fields(ctx.db)
+            .iter()
+            .enumerate()
+            .map(|(idx, field)| (field.name(ctx.db).to_string(), idx))
+            .collect(),
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn not_applicable_if_sorted() {
+        check_assist_not_applicable(
+            reorder_fields,
+            r#"
+        struct Foo {
+            foo: i32,
+            bar: i32,
+        }
+
+        const test: Foo = <|>Foo { foo: 0, bar: 0 };
+        "#,
+        )
+    }
+
+    #[test]
+    fn trivial_empty_fields() {
+        check_assist_not_applicable(
+            reorder_fields,
+            r#"
+        struct Foo {};
+        const test: Foo = <|>Foo {}
+        "#,
+        )
+    }
+
+    #[test]
+    fn reorder_struct_fields() {
+        check_assist(
+            reorder_fields,
+            r#"
+        struct Foo {foo: i32, bar: i32};
+        const test: Foo = <|>Foo {bar: 0, foo: 1}
+        "#,
+            r#"
+        struct Foo {foo: i32, bar: i32};
+        const test: Foo = <|>Foo {foo: 1, bar: 0}
+        "#,
+        )
+    }
+
+    #[test]
+    fn reorder_struct_pattern() {
+        check_assist(
+            reorder_fields,
+            r#"
+        struct Foo { foo: i64, bar: i64, baz: i64 }
+
+        fn f(f: Foo) -> {
+            match f {
+                <|>Foo { baz: 0, ref mut bar, .. } => (),
+                _ => ()
+            }
+        }
+        "#,
+            r#"
+        struct Foo { foo: i64, bar: i64, baz: i64 }
+
+        fn f(f: Foo) -> {
+            match f {
+                <|>Foo { ref mut bar, baz: 0, .. } => (),
+                _ => ()
+            }
+        }
+        "#,
+        )
+    }
+
+    #[test]
+    fn reorder_with_extra_field() {
+        check_assist(
+            reorder_fields,
+            r#"
+            struct Foo {
+                foo: String,
+                bar: String,
+            }
+
+            impl Foo {
+                fn new() -> Foo {
+                    let foo = String::new();
+                    <|>Foo {
+                        bar: foo.clone(),
+                        extra: "Extra field",
+                        foo,
+                    }
+                }
+            }
+            "#,
+            r#"
+            struct Foo {
+                foo: String,
+                bar: String,
+            }
+
+            impl Foo {
+                fn new() -> Foo {
+                    let foo = String::new();
+                    <|>Foo {
+                        foo,
+                        bar: foo.clone(),
+                        extra: "Extra field",
+                    }
+                }
+            }
+            "#,
+        )
+    }
+}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 5ba5254fd..a00136da1 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -129,6 +129,7 @@ mod handlers {
     mod replace_unwrap_with_match;
     mod split_import;
     mod add_from_impl_for_enum;
+    mod reorder_fields;
 
     pub(crate) fn all() -> &'static [AssistHandler] {
         &[
@@ -170,6 +171,7 @@ mod handlers {
             // These are manually sorted for better priorities
             add_missing_impl_members::add_missing_impl_members,
             add_missing_impl_members::add_missing_default_members,
+            reorder_fields::reorder_fields,
         ]
     }
 }
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index b0d71eb3d..80492b733 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -689,9 +689,10 @@ impl ExprCollector<'_> {
                     Pat::Missing
                 }
             }
-
             // FIXME: implement
             ast::Pat::BoxPat(_) | ast::Pat::RangePat(_) | ast::Pat::MacroPat(_) => Pat::Missing,
+            // FIXME: implement
+            ast::Pat::RecordFieldPat(_) => Pat::Missing,
         };
         let ptr = AstPtr::new(&pat);
         self.alloc_pat(pattern, Either::Left(ptr))
diff --git a/crates/ra_syntax/src/ast/generated/nodes.rs b/crates/ra_syntax/src/ast/generated/nodes.rs
index 20f663046..79b225622 100644
--- a/crates/ra_syntax/src/ast/generated/nodes.rs
+++ b/crates/ra_syntax/src/ast/generated/nodes.rs
@@ -3256,6 +3256,7 @@ pub enum Pat {
     RangePat(RangePat),
     LiteralPat(LiteralPat),
     MacroPat(MacroPat),
+    RecordFieldPat(RecordFieldPat),
 }
 impl From<OrPat> for Pat {
     fn from(node: OrPat) -> Pat { Pat::OrPat(node) }
@@ -3302,12 +3303,15 @@ impl From<LiteralPat> for Pat {
 impl From<MacroPat> for Pat {
     fn from(node: MacroPat) -> Pat { Pat::MacroPat(node) }
 }
+impl From<RecordFieldPat> for Pat {
+    fn from(node: RecordFieldPat) -> Pat { Pat::RecordFieldPat(node) }
+}
 impl AstNode for Pat {
     fn can_cast(kind: SyntaxKind) -> bool {
         match kind {
             OR_PAT | PAREN_PAT | REF_PAT | BOX_PAT | BIND_PAT | PLACEHOLDER_PAT | DOT_DOT_PAT
             | PATH_PAT | RECORD_PAT | TUPLE_STRUCT_PAT | TUPLE_PAT | SLICE_PAT | RANGE_PAT
-            | LITERAL_PAT | MACRO_PAT => true,
+            | LITERAL_PAT | MACRO_PAT | RECORD_FIELD_PAT => true,
             _ => false,
         }
     }
@@ -3328,6 +3332,7 @@ impl AstNode for Pat {
             RANGE_PAT => Pat::RangePat(RangePat { syntax }),
             LITERAL_PAT => Pat::LiteralPat(LiteralPat { syntax }),
             MACRO_PAT => Pat::MacroPat(MacroPat { syntax }),
+            RECORD_FIELD_PAT => Pat::RecordFieldPat(RecordFieldPat { syntax }),
             _ => return None,
         };
         Some(res)
@@ -3349,6 +3354,7 @@ impl AstNode for Pat {
             Pat::RangePat(it) => &it.syntax,
             Pat::LiteralPat(it) => &it.syntax,
             Pat::MacroPat(it) => &it.syntax,
+            Pat::RecordFieldPat(it) => &it.syntax,
         }
     }
 }