1 files changed, 80 insertions, 0 deletions

diff --git a/crates/ra_ide/src/completion/complete_impl_fn.rs b/crates/ra_ide/src/completion/complete_impl_fn.rs
new file mode 100644
index 000000000..6d464cc1f
--- /dev/null
+++ b/crates/ra_ide/src/completion/complete_impl_fn.rs
@@ -0,0 +1,80 @@
+
+use crate::completion::{CompletionContext, Completions};
+
+use hir::{ self, db::HirDatabase, HasSource };
+
+use ra_syntax::{ ast, ast::AstNode };
+
+pub(crate) fn complete_impl_fn(acc: &mut Completions, ctx: &CompletionContext) {
+    let impl_trait = ast::ItemList::cast(ctx.token.parent())
+        .and_then(|item_list| item_list.syntax().parent())
+        .and_then(|item_list_parent| ast::ImplBlock::cast(item_list_parent))
+        .and_then(|impl_block| resolve_target_trait(ctx.db, &ctx.analyzer, &impl_block));
+
+    if let Some(x) = &impl_trait {
+        for trait_item in x.0.items(ctx.db) {
+            match trait_item {
+                hir::AssocItem::Function(f) => acc.add_function_impl(ctx, f),
+                _ => {}
+            }
+        }
+    }
+}
+
+fn resolve_target_trait(
+    db: &impl HirDatabase,
+    analyzer: &hir::SourceAnalyzer,
+    impl_block: &ast::ImplBlock
+) -> Option<(hir::Trait, ast::TraitDef)> {
+    let ast_path = impl_block
+        .target_trait()
+        .map(|it| it.syntax().clone())
+        .and_then(ast::PathType::cast)?
+        .path()?;
+
+    match analyzer.resolve_path(db, &ast_path) {
+        Some(hir::PathResolution::Def(hir::ModuleDef::Trait(def))) => {
+            Some((def, def.source(db).value))
+        }
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::completion::{do_completion, CompletionItem, CompletionKind};
+    use insta::assert_debug_snapshot;
+
+    fn complete(code: &str) -> Vec<CompletionItem> {
+        do_completion(code, CompletionKind::Reference)
+    }
+
+    #[test]
+    fn single_function() {
+        let completions = complete(
+            r"
+            trait Test {
+                fn foo();
+            }
+
+            struct T1;
+
+            impl Test for T1 {
+                <|>
+            }
+            ",
+        );
+        assert_debug_snapshot!(completions, @r###"
+        [
+            CompletionItem {
+                label: "fn foo()",
+                source_range: [138; 138),
+                delete: [138; 138),
+                insert: "fn foo() { $0 }",
+                kind: Function,
+                lookup: "foo",
+            },
+        ]
+        "###);
+    }
+}
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