provide completion in struct patterns

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(),
     }