8 files changed, 363 insertions, 74 deletions

diff --git a/crates/completion/src/completions.rs b/crates/completion/src/completions.rs
index 1ef6b5f48..d9fe13485 100644
--- a/crates/completion/src/completions.rs
+++ b/crates/completion/src/completions.rs
@@ -19,9 +19,14 @@ use hir::{ModPath, ScopeDef, Type};
 use crate::{
     item::Builder,
     render::{
-        const_::render_const, enum_variant::render_variant, function::render_fn,
-        macro_::render_macro, render_field, render_resolution, render_tuple_field,
-        type_alias::render_type_alias, RenderContext,
+        const_::render_const,
+        enum_variant::render_variant,
+        function::render_fn,
+        macro_::render_macro,
+        pattern::{render_struct_pat, render_variant_pat},
+        render_field, render_resolution, render_tuple_field,
+        type_alias::render_type_alias,
+        RenderContext,
     },
     CompletionContext, CompletionItem,
 };
@@ -105,6 +110,28 @@ impl Completions {
         self.add(item)
     }
 
+    pub(crate) fn add_variant_pat(
+        &mut self,
+        ctx: &CompletionContext,
+        variant: hir::Variant,
+        local_name: Option<hir::Name>,
+    ) {
+        if let Some(item) = render_variant_pat(RenderContext::new(ctx), variant, local_name) {
+            self.add(item);
+        }
+    }
+
+    pub(crate) fn add_struct_pat(
+        &mut self,
+        ctx: &CompletionContext,
+        strukt: hir::Struct,
+        local_name: Option<hir::Name>,
+    ) {
+        if let Some(item) = render_struct_pat(RenderContext::new(ctx), strukt, local_name) {
+            self.add(item);
+        }
+    }
+
     pub(crate) fn add_const(&mut self, ctx: &CompletionContext, constant: hir::Const) {
         if let Some(item) = render_const(RenderContext::new(ctx), constant) {
             self.add(item);
diff --git a/crates/completion/src/completions/pattern.rs b/crates/completion/src/completions/pattern.rs
index 4d56731ec..eee31098d 100644
--- a/crates/completion/src/completions/pattern.rs
+++ b/crates/completion/src/completions/pattern.rs
@@ -2,9 +2,9 @@
 
 use crate::{CompletionContext, Completions};
 
-/// Completes constats and paths in patterns.
+/// Completes constants and paths in patterns.
 pub(crate) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
-    if !(ctx.is_pat_binding_or_const || ctx.is_irrefutable_let_pat_binding) {
+    if !(ctx.is_pat_binding_or_const || ctx.is_irrefutable_pat_binding) {
         return;
     }
     if ctx.record_pat_syntax.is_some() {
@@ -15,20 +15,21 @@ pub(crate) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
     // suggest variants + auto-imports
     ctx.scope.process_all_names(&mut |name, res| {
         let add_resolution = match &res {
-            hir::ScopeDef::ModuleDef(def) => {
-                if ctx.is_irrefutable_let_pat_binding {
-                    matches!(def, hir::ModuleDef::Adt(hir::Adt::Struct(_)))
-                } else {
-                    matches!(
-                        def,
-                        hir::ModuleDef::Adt(hir::Adt::Enum(..))
-                            | hir::ModuleDef::Adt(hir::Adt::Struct(..))
-                            | hir::ModuleDef::Variant(..)
-                            | hir::ModuleDef::Const(..)
-                            | hir::ModuleDef::Module(..)
-                    )
+            hir::ScopeDef::ModuleDef(def) => match def {
+                hir::ModuleDef::Adt(hir::Adt::Struct(strukt)) => {
+                    acc.add_struct_pat(ctx, strukt.clone(), Some(name.clone()));
+                    true
                 }
-            }
+                hir::ModuleDef::Variant(variant) if !ctx.is_irrefutable_pat_binding => {
+                    acc.add_variant_pat(ctx, variant.clone(), Some(name.clone()));
+                    true
+                }
+                hir::ModuleDef::Adt(hir::Adt::Enum(..))
+                | hir::ModuleDef::Variant(..)
+                | hir::ModuleDef::Const(..)
+                | hir::ModuleDef::Module(..) => !ctx.is_irrefutable_pat_binding,
+                _ => false,
+            },
             hir::ScopeDef::MacroDef(_) => true,
             _ => false,
         };
@@ -42,13 +43,21 @@ pub(crate) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
 mod tests {
     use expect_test::{expect, Expect};
 
-    use crate::{test_utils::completion_list, CompletionKind};
+    use crate::{
+        test_utils::{check_edit, completion_list},
+        CompletionKind,
+    };
 
     fn check(ra_fixture: &str, expect: Expect) {
         let actual = completion_list(ra_fixture, CompletionKind::Reference);
         expect.assert_eq(&actual)
     }
 
+    fn check_snippet(ra_fixture: &str, expect: Expect) {
+        let actual = completion_list(ra_fixture, CompletionKind::Snippet);
+        expect.assert_eq(&actual)
+    }
+
     #[test]
     fn completes_enum_variants_and_modules() {
         check(
@@ -69,7 +78,7 @@ fn foo() {
                 en E
                 ct Z
                 st Bar
-                ev X   ()
+                ev X
                 md m
             "#]],
         );
@@ -114,4 +123,139 @@ fn foo() {
             "#]],
         );
     }
+
+    #[test]
+    fn completes_in_param() {
+        check(
+            r#"
+enum E { X }
+
+static FOO: E = E::X;
+struct Bar { f: u32 }
+
+fn foo(<|>) {
+}
+"#,
+            expect![[r#"
+                st Bar
+            "#]],
+        );
+    }
+
+    #[test]
+    fn completes_pat_in_let() {
+        check_snippet(
+            r#"
+struct Bar { f: u32 }
+
+fn foo() {
+   let <|>
+}
+"#,
+            expect![[r#"
+                bn Bar Bar { f$1 }$0
+            "#]],
+        );
+    }
+
+    #[test]
+    fn completes_param_pattern() {
+        check_snippet(
+            r#"
+struct Foo { bar: String, baz: String }
+struct Bar(String, String);
+struct Baz;
+fn outer(<|>) {}
+"#,
+            expect![[r#"
+                bn Foo Foo { bar$1, baz$2 }: Foo$0
+                bn Bar Bar($1, $2): Bar$0
+            "#]],
+        )
+    }
+
+    #[test]
+    fn completes_let_pattern() {
+        check_snippet(
+            r#"
+struct Foo { bar: String, baz: String }
+struct Bar(String, String);
+struct Baz;
+fn outer() {
+    let <|>
+}
+"#,
+            expect![[r#"
+                bn Foo Foo { bar$1, baz$2 }$0
+                bn Bar Bar($1, $2)$0
+            "#]],
+        )
+    }
+
+    #[test]
+    fn completes_refutable_pattern() {
+        check_snippet(
+            r#"
+struct Foo { bar: i32, baz: i32 }
+struct Bar(String, String);
+struct Baz;
+fn outer() {
+    match () {
+        <|>
+    }
+}
+"#,
+            expect![[r#"
+                bn Foo Foo { bar$1, baz$2 }$0
+                bn Bar Bar($1, $2)$0
+            "#]],
+        )
+    }
+
+    #[test]
+    fn omits_private_fields_pat() {
+        check_snippet(
+            r#"
+mod foo {
+    pub struct Foo { pub bar: i32, baz: i32 }
+    pub struct Bar(pub String, String);
+    pub struct Invisible(String, String);
+}
+use foo::*;
+
+fn outer() {
+    match () {
+        <|>
+    }
+}
+"#,
+            expect![[r#"
+                bn Foo Foo { bar$1, .. }$0
+                bn Bar Bar($1, ..)$0
+            "#]],
+        )
+    }
+
+    #[test]
+    fn only_shows_ident_completion() {
+        check_edit(
+            "Foo",
+            r#"
+struct Foo(i32);
+fn main() {
+    match Foo(92) {
+        <|>(92) => (),
+    }
+}
+"#,
+            r#"
+struct Foo(i32);
+fn main() {
+    match Foo(92) {
+        Foo(92) => (),
+    }
+}
+"#,
+        );
+    }
 }
diff --git a/crates/completion/src/context.rs b/crates/completion/src/context.rs
index 5cd11cf77..41de324d8 100644
--- a/crates/completion/src/context.rs
+++ b/crates/completion/src/context.rs
@@ -51,7 +51,7 @@ pub(crate) struct CompletionContext<'a> {
     /// If a name-binding or reference to a const in a pattern.
     /// Irrefutable patterns (like let) are excluded.
     pub(super) is_pat_binding_or_const: bool,
-    pub(super) is_irrefutable_let_pat_binding: bool,
+    pub(super) is_irrefutable_pat_binding: bool,
     /// A single-indent path, like `foo`. `::foo` should not be considered a trivial path.
     pub(super) is_trivial_path: bool,
     /// If not a trivial path, the prefix (qualifier).
@@ -147,7 +147,7 @@ impl<'a> CompletionContext<'a> {
             active_parameter: ActiveParameter::at(db, position),
             is_param: false,
             is_pat_binding_or_const: false,
-            is_irrefutable_let_pat_binding: false,
+            is_irrefutable_pat_binding: false,
             is_trivial_path: false,
             path_qual: None,
             after_if: false,
@@ -327,14 +327,19 @@ impl<'a> CompletionContext<'a> {
                 if bind_pat.syntax().parent().and_then(ast::RecordPatFieldList::cast).is_some() {
                     self.is_pat_binding_or_const = false;
                 }
-                if let Some(let_stmt) = bind_pat.syntax().ancestors().find_map(ast::LetStmt::cast) {
-                    if let Some(pat) = let_stmt.pat() {
-                        if pat.syntax().text_range().contains_range(bind_pat.syntax().text_range())
-                        {
-                            self.is_pat_binding_or_const = false;
-                            self.is_irrefutable_let_pat_binding = true;
+                if let Some(Some(pat)) = bind_pat.syntax().ancestors().find_map(|node| {
+                    match_ast! {
+                        match node {
+                            ast::LetStmt(it) => Some(it.pat()),
+                            ast::Param(it) => Some(it.pat()),
+                            _ => None,
                         }
                     }
+                }) {
+                    if pat.syntax().text_range().contains_range(bind_pat.syntax().text_range()) {
+                        self.is_pat_binding_or_const = false;
+                        self.is_irrefutable_pat_binding = true;
+                    }
                 }
             }
             if is_node::<ast::Param>(name.syntax()) {
diff --git a/crates/completion/src/render.rs b/crates/completion/src/render.rs
index 1092a4825..1ba7201a1 100644
--- a/crates/completion/src/render.rs
+++ b/crates/completion/src/render.rs
@@ -5,6 +5,7 @@ pub(crate) mod macro_;
 pub(crate) mod function;
 pub(crate) mod enum_variant;
 pub(crate) mod const_;
+pub(crate) mod pattern;
 pub(crate) mod type_alias;
 
 mod builder_ext;
@@ -159,6 +160,12 @@ impl<'a> Render<'a> {
                 let item = render_fn(self.ctx, import_to_add, Some(local_name), *func);
                 return Some(item);
             }
+            ScopeDef::ModuleDef(Variant(_))
+                if self.ctx.completion.is_pat_binding_or_const
+                    | self.ctx.completion.is_irrefutable_pat_binding =>
+            {
+                CompletionItemKind::EnumVariant
+            }
             ScopeDef::ModuleDef(Variant(var)) => {
                 let item = render_variant(self.ctx, import_to_add, Some(local_name), *var, None);
                 return Some(item);
diff --git a/crates/completion/src/render/builder_ext.rs b/crates/completion/src/render/builder_ext.rs
index ce8718bd5..d053a988b 100644
--- a/crates/completion/src/render/builder_ext.rs
+++ b/crates/completion/src/render/builder_ext.rs
@@ -34,7 +34,6 @@ impl Builder {
             return false;
         }
         if ctx.is_pattern_call {
-            mark::hit!(dont_duplicate_pattern_parens);
             return false;
         }
         if ctx.is_call {
diff --git a/crates/completion/src/render/enum_variant.rs b/crates/completion/src/render/enum_variant.rs
index 7176fd9b3..732e139ec 100644
--- a/crates/completion/src/render/enum_variant.rs
+++ b/crates/completion/src/render/enum_variant.rs
@@ -126,50 +126,5 @@ fn main() -> Option<i32> {
 }
 "#,
         );
-        check_edit(
-            "Some",
-            r#"
-enum Option<T> { Some(T), None }
-use Option::*;
-fn main(value: Option<i32>) {
-    match value {
-        Som<|>
-    }
-}
-"#,
-            r#"
-enum Option<T> { Some(T), None }
-use Option::*;
-fn main(value: Option<i32>) {
-    match value {
-        Some($0)
-    }
-}
-"#,
-        );
-    }
-
-    #[test]
-    fn dont_duplicate_pattern_parens() {
-        mark::check!(dont_duplicate_pattern_parens);
-        check_edit(
-            "Var",
-            r#"
-enum E { Var(i32) }
-fn main() {
-    match E::Var(92) {
-        E::<|>(92) => (),
-    }
-}
-"#,
-            r#"
-enum E { Var(i32) }
-fn main() {
-    match E::Var(92) {
-        E::Var(92) => (),
-    }
-}
-"#,
-        );
     }
 }
diff --git a/crates/completion/src/render/pattern.rs b/crates/completion/src/render/pattern.rs
new file mode 100644
index 000000000..a3b6a3cac
--- /dev/null
+++ b/crates/completion/src/render/pattern.rs
@@ -0,0 +1,148 @@
+//! Renderer for patterns.
+
+use hir::{db::HirDatabase, HasAttrs, HasVisibility, Name, StructKind};
+use itertools::Itertools;
+
+use crate::{
+    config::SnippetCap, item::CompletionKind, render::RenderContext, CompletionItem,
+    CompletionItemKind,
+};
+
+fn visible_fields(
+    ctx: &RenderContext<'_>,
+    fields: &[hir::Field],
+    item: impl HasAttrs,
+) -> Option<(Vec<hir::Field>, bool)> {
+    let module = ctx.completion.scope.module()?;
+    let n_fields = fields.len();
+    let fields = fields
+        .into_iter()
+        .filter(|field| field.is_visible_from(ctx.db(), module))
+        .copied()
+        .collect::<Vec<_>>();
+
+    let fields_omitted =
+        n_fields - fields.len() > 0 || item.attrs(ctx.db()).by_key("non_exhaustive").exists();
+    Some((fields, fields_omitted))
+}
+
+pub(crate) fn render_struct_pat(
+    ctx: RenderContext<'_>,
+    strukt: hir::Struct,
+    local_name: Option<Name>,
+) -> Option<CompletionItem> {
+    let _p = profile::span("render_struct_pat");
+
+    let fields = strukt.fields(ctx.db());
+    let (visible_fields, fields_omitted) = visible_fields(&ctx, &fields, strukt)?;
+
+    if visible_fields.is_empty() {
+        // Matching a struct without matching its fields is pointless, unlike matching a Variant without its fields
+        return None;
+    }
+
+    let name = local_name.unwrap_or_else(|| strukt.name(ctx.db())).to_string();
+    let pat = render_pat(&ctx, &name, strukt.kind(ctx.db()), &visible_fields, fields_omitted)?;
+
+    Some(build_completion(ctx, name, pat, strukt))
+}
+
+pub(crate) fn render_variant_pat(
+    ctx: RenderContext<'_>,
+    variant: hir::Variant,
+    local_name: Option<Name>,
+) -> Option<CompletionItem> {
+    let _p = profile::span("render_variant_pat");
+
+    let fields = variant.fields(ctx.db());
+    let (visible_fields, fields_omitted) = visible_fields(&ctx, &fields, variant)?;
+
+    let name = local_name.unwrap_or_else(|| variant.name(ctx.db())).to_string();
+    let pat = render_pat(&ctx, &name, variant.kind(ctx.db()), &visible_fields, fields_omitted)?;
+
+    Some(build_completion(ctx, name, pat, variant))
+}
+
+fn build_completion(
+    ctx: RenderContext<'_>,
+    name: String,
+    pat: String,
+    item: impl HasAttrs + Copy,
+) -> CompletionItem {
+    let completion = CompletionItem::new(CompletionKind::Snippet, ctx.source_range(), name)
+        .kind(CompletionItemKind::Binding)
+        .set_documentation(ctx.docs(item))
+        .set_deprecated(ctx.is_deprecated(item))
+        .detail(&pat);
+    let completion = if let Some(snippet_cap) = ctx.snippet_cap() {
+        completion.insert_snippet(snippet_cap, pat)
+    } else {
+        completion.insert_text(pat)
+    };
+    completion.build()
+}
+
+fn render_pat(
+    ctx: &RenderContext<'_>,
+    name: &str,
+    kind: StructKind,
+    fields: &[hir::Field],
+    fields_omitted: bool,
+) -> Option<String> {
+    let mut pat = match kind {
+        StructKind::Tuple if ctx.snippet_cap().is_some() => {
+            render_tuple_as_pat(&fields, &name, fields_omitted)
+        }
+        StructKind::Record => {
+            render_record_as_pat(ctx.db(), ctx.snippet_cap(), &fields, &name, fields_omitted)
+        }
+        _ => return None,
+    };
+
+    if ctx.completion.is_param {
+        pat.push(':');
+        pat.push(' ');
+        pat.push_str(&name);
+    }
+    if ctx.snippet_cap().is_some() {
+        pat.push_str("$0");
+    }
+    Some(pat)
+}
+
+fn render_record_as_pat(
+    db: &dyn HirDatabase,
+    snippet_cap: Option<SnippetCap>,
+    fields: &[hir::Field],
+    name: &str,
+    fields_omitted: bool,
+) -> String {
+    let fields = fields.iter();
+    if snippet_cap.is_some() {
+        format!(
+            "{name} {{ {}{} }}",
+            fields
+                .enumerate()
+                .map(|(idx, field)| format!("{}${}", field.name(db), idx + 1))
+                .format(", "),
+            if fields_omitted { ", .." } else { "" },
+            name = name
+        )
+    } else {
+        format!(
+            "{name} {{ {}{} }}",
+            fields.map(|field| field.name(db)).format(", "),
+            if fields_omitted { ", .." } else { "" },
+            name = name
+        )
+    }
+}
+
+fn render_tuple_as_pat(fields: &[hir::Field], name: &str, fields_omitted: bool) -> String {
+    format!(
+        "{name}({}{})",
+        fields.iter().enumerate().map(|(idx, _)| format!("${}", idx + 1)).format(", "),
+        if fields_omitted { ", .." } else { "" },
+        name = name
+    )
+}
diff --git a/crates/hir/src/code_model.rs b/crates/hir/src/code_model.rs
index 73ca6ba9f..1d7e5ddd7 100644
--- a/crates/hir/src/code_model.rs
+++ b/crates/hir/src/code_model.rs
@@ -511,6 +511,10 @@ impl Struct {
         db.struct_data(self.id).repr.clone()
     }
 
+    pub fn kind(self, db: &dyn HirDatabase) -> StructKind {
+        self.variant_data(db).kind()
+    }
+
     fn variant_data(self, db: &dyn HirDatabase) -> Arc<VariantData> {
         db.struct_data(self.id).variant_data.clone()
     }