Provide completion in struct patterns

crates/ra_hir/src/source_binder.rs

@@ -266,9 +266,14 @@ impl SourceAnalyzer {
         self.infer.as_ref()?.field_resolution(expr_id)
     }
 
-    pub fn resolve_variant(&self, struct_lit: &ast::StructLit) -> Option<crate::VariantDef> {
+    pub fn resolve_struct_literal(&self, struct_lit: &ast::StructLit) -> Option<crate::VariantDef> {
         let expr_id = self.body_source_map.as_ref()?.node_expr(&struct_lit.clone().into())?;
-        self.infer.as_ref()?.variant_resolution(expr_id)
+        self.infer.as_ref()?.variant_resolution_for_expr(expr_id)
+    }
+
+    pub fn resolve_struct_pattern(&self, struct_pat: &ast::StructPat) -> Option<crate::VariantDef> {
+        let pat_id = self.body_source_map.as_ref()?.node_pat(&struct_pat.clone().into())?;
+        self.infer.as_ref()?.variant_resolution_for_pat(pat_id)
     }
 
     pub fn resolve_macro_call(

crates/ra_hir/src/ty.rs

@@ -472,7 +472,7 @@ impl Ty {
 
     /// Returns the type parameters of this type if it has some (i.e. is an ADT
     /// or function); so if `self` is `Option<u32>`, this returns the `u32`.
-    fn substs(&self) -> Option<Substs> {
+    pub fn substs(&self) -> Option<Substs> {
         match self {
             Ty::Apply(ApplicationTy { parameters, .. }) => Some(parameters.clone()),
             _ => None,

crates/ra_hir/src/ty/infer.rs

@@ -113,7 +113,8 @@ pub struct InferenceResult {
     method_resolutions: FxHashMap<ExprId, Function>,
     /// For each field access expr, records the field it resolves to.
     field_resolutions: FxHashMap<ExprId, StructField>,
-    variant_resolutions: FxHashMap<ExprId, VariantDef>,
+    /// For each struct literal, records the variant it resolves to.
+    variant_resolutions: FxHashMap<ExprOrPatId, VariantDef>,
     /// For each associated item record what it resolves to
     assoc_resolutions: FxHashMap<ExprOrPatId, ImplItem>,
     diagnostics: Vec<InferenceDiagnostic>,
@@ -128,8 +129,11 @@ impl InferenceResult {
     pub fn field_resolution(&self, expr: ExprId) -> Option<StructField> {
         self.field_resolutions.get(&expr).copied()
     }
-    pub fn variant_resolution(&self, expr: ExprId) -> Option<VariantDef> {
-        self.variant_resolutions.get(&expr).copied()
+    pub fn variant_resolution_for_expr(&self, id: ExprId) -> Option<VariantDef> {
+        self.variant_resolutions.get(&id.into()).copied()
+    }
+    pub fn variant_resolution_for_pat(&self, id: PatId) -> Option<VariantDef> {
+        self.variant_resolutions.get(&id.into()).copied()
     }
     pub fn assoc_resolutions_for_expr(&self, id: ExprId) -> Option<ImplItem> {
         self.assoc_resolutions.get(&id.into()).copied()
@@ -218,8 +222,8 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.result.field_resolutions.insert(expr, field);
     }
 
-    fn write_variant_resolution(&mut self, expr: ExprId, variant: VariantDef) {
-        self.result.variant_resolutions.insert(expr, variant);
+    fn write_variant_resolution(&mut self, id: ExprOrPatId, variant: VariantDef) {
+        self.result.variant_resolutions.insert(id, variant);
     }
 
     fn write_assoc_resolution(&mut self, id: ExprOrPatId, item: ImplItem) {
@@ -678,8 +682,12 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         subpats: &[FieldPat],
         expected: &Ty,
         default_bm: BindingMode,
+        id: PatId,
     ) -> Ty {
         let (ty, def) = self.resolve_variant(path);
+        if let Some(variant) = def {
+            self.write_variant_resolution(id.into(), variant);
+        }
 
         self.unify(&ty, expected);
 
@@ -762,7 +770,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 self.infer_tuple_struct_pat(p.as_ref(), subpats, expected, default_bm)
             }
             Pat::Struct { path: ref p, args: ref fields } => {
-                self.infer_struct_pat(p.as_ref(), fields, expected, default_bm)
+                self.infer_struct_pat(p.as_ref(), fields, expected, default_bm, pat)
             }
             Pat::Path(path) => {
                 // FIXME use correct resolver for the surrounding expression
@@ -1064,7 +1072,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             Expr::StructLit { path, fields, spread } => {
                 let (ty, def_id) = self.resolve_variant(path.as_ref());
                 if let Some(variant) = def_id {
-                    self.write_variant_resolution(tgt_expr, variant);
+                    self.write_variant_resolution(tgt_expr.into(), variant);
                 }
 
                 let substs = ty.substs().unwrap_or_else(Substs::empty);

crates/ra_ide_api/src/completion.rs

@@ -4,6 +4,7 @@ mod presentation;
 
 mod complete_dot;
 mod complete_struct_literal;
+mod complete_struct_pattern;
 mod complete_pattern;
 mod complete_fn_param;
 mod complete_keyword;
@@ -65,6 +66,7 @@ pub(crate) fn completions(db: &db::RootDatabase, position: FilePosition) -> Opti
     complete_scope::complete_scope(&mut acc, &ctx);
     complete_dot::complete_dot(&mut acc, &ctx);
     complete_struct_literal::complete_struct_literal(&mut acc, &ctx);
+    complete_struct_pattern::complete_struct_pattern(&mut acc, &ctx);
     complete_pattern::complete_pattern(&mut acc, &ctx);
     complete_postfix::complete_postfix(&mut acc, &ctx);
     Some(acc)

crates/ra_ide_api/src/completion/complete_struct_literal.rs

@@ -1,23 +1,22 @@
-use hir::{Substs, Ty};
+use hir::Substs;
 
 use crate::completion::{CompletionContext, Completions};
 
 /// Complete fields in fields literals.
 pub(super) fn complete_struct_literal(acc: &mut Completions, ctx: &CompletionContext) {
     let (ty, variant) = match ctx.struct_lit_syntax.as_ref().and_then(|it| {
-        Some((ctx.analyzer.type_of(ctx.db, &it.clone().into())?, ctx.analyzer.resolve_variant(it)?))
+        Some((
+            ctx.analyzer.type_of(ctx.db, &it.clone().into())?,
+            ctx.analyzer.resolve_struct_literal(it)?,
+        ))
     }) {
         Some(it) => it,
         _ => return,
     };
-
-    let ty_substs = match ty {
-        Ty::Apply(it) => it.parameters,
-        _ => Substs::empty(),
-    };
+    let substs = &ty.substs().unwrap_or_else(Substs::empty);
 
     for field in variant.fields(ctx.db) {
-        acc.add_field(ctx, field, &ty_substs);
+        acc.add_field(ctx, field, substs);
     }
 }
 

crates/ra_ide_api/src/completion/complete_struct_pattern.rs

@@ -0,0 +1,94 @@
+use hir::Substs;
+
+use crate::completion::{CompletionContext, Completions};
+
+pub(super) fn complete_struct_pattern(acc: &mut Completions, ctx: &CompletionContext) {
+    let (ty, variant) = match ctx.struct_lit_pat.as_ref().and_then(|it| {
+        Some((
+            ctx.analyzer.type_of_pat(ctx.db, &it.clone().into())?,
+            ctx.analyzer.resolve_struct_pattern(it)?,
+        ))
+    }) {
+        Some(it) => it,
+        _ => return,
+    };
+    let substs = &ty.substs().unwrap_or_else(Substs::empty);
+
+    for field in variant.fields(ctx.db) {
+        acc.add_field(ctx, field, substs);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{do_completion, CompletionItem, CompletionKind};
+    use insta::assert_debug_snapshot_matches;
+
+    fn complete(code: &str) -> Vec<CompletionItem> {
+        do_completion(code, CompletionKind::Reference)
+    }
+
+    #[test]
+    fn test_struct_pattern_field() {
+        let completions = complete(
+            r"
+            struct S { foo: u32 }
+
+            fn process(f: S) {
+                match f {
+                    S { f<|>: 92 } => (),
+                }
+            }
+            ",
+        );
+        assert_debug_snapshot_matches!(completions, @r###"
+       ⋮[
+       ⋮    CompletionItem {
+       ⋮        label: "foo",
+       ⋮        source_range: [117; 118),
+       ⋮        delete: [117; 118),
+       ⋮        insert: "foo",
+       ⋮        kind: Field,
+       ⋮        detail: "u32",
+       ⋮    },
+       ⋮]
+        "###);
+    }
+
+    #[test]
+    fn test_struct_pattern_enum_variant() {
+        let completions = complete(
+            r"
+            enum E {
+                S { foo: u32, bar: () }
+            }
+
+            fn process(e: E) {
+                match e {
+                    E::S { <|> } => (),
+                }
+            }
+            ",
+        );
+        assert_debug_snapshot_matches!(completions, @r###"
+       ⋮[
+       ⋮    CompletionItem {
+       ⋮        label: "bar",
+       ⋮        source_range: [161; 161),
+       ⋮        delete: [161; 161),
+       ⋮        insert: "bar",
+       ⋮        kind: Field,
+       ⋮        detail: "()",
+       ⋮    },
+       ⋮    CompletionItem {
+       ⋮        label: "foo",
+       ⋮        source_range: [161; 161),
+       ⋮        delete: [161; 161),
+       ⋮        insert: "foo",
+       ⋮        kind: Field,
+       ⋮        detail: "u32",
+       ⋮    },
+       ⋮]
+        "###);
+    }
+}

crates/ra_ide_api/src/completion/completion_context.rs

@@ -21,6 +21,7 @@ pub(crate) struct CompletionContext<'a> {
     pub(super) function_syntax: Option<ast::FnDef>,
     pub(super) use_item_syntax: Option<ast::UseItem>,
     pub(super) struct_lit_syntax: Option<ast::StructLit>,
+    pub(super) struct_lit_pat: Option<ast::StructPat>,
     pub(super) is_param: bool,
     /// If a name-binding or reference to a const in a pattern.
     /// Irrefutable patterns (like let) are excluded.
@@ -60,6 +61,7 @@ impl<'a> CompletionContext<'a> {
             function_syntax: None,
             use_item_syntax: None,
             struct_lit_syntax: None,
+            struct_lit_pat: None,
             is_param: false,
             is_pat_binding: false,
             is_trivial_path: false,
@@ -106,8 +108,7 @@ impl<'a> CompletionContext<'a> {
         // Otherwise, see if this is a declaration. We can use heuristics to
         // suggest declaration names, see `CompletionKind::Magic`.
         if let Some(name) = find_node_at_offset::<ast::Name>(file.syntax(), offset) {
-            if is_node::<ast::BindPat>(name.syntax()) {
-                let bind_pat = name.syntax().ancestors().find_map(ast::BindPat::cast).unwrap();
+            if let Some(bind_pat) = name.syntax().ancestors().find_map(ast::BindPat::cast) {
                 let parent = bind_pat.syntax().parent();
                 if parent.clone().and_then(ast::MatchArm::cast).is_some()
                     || parent.and_then(ast::Condition::cast).is_some()
@@ -119,6 +120,10 @@ impl<'a> CompletionContext<'a> {
                 self.is_param = true;
                 return;
             }
+            if name.syntax().ancestors().find_map(ast::FieldPatList::cast).is_some() {
+                self.struct_lit_pat =
+                    find_node_at_offset(original_parse.tree().syntax(), self.offset);
+            }
         }
     }
 
@@ -235,7 +240,7 @@ fn find_node_with_range<N: AstNode>(syntax: &SyntaxNode, range: TextRange) -> Op
 }
 
 fn is_node<N: AstNode>(node: &SyntaxNode) -> bool {
-    match node.ancestors().filter_map(N::cast).next() {
+    match node.ancestors().find_map(N::cast) {
         None => false,
         Some(n) => n.syntax().text_range() == node.text_range(),
     }