1 files changed, 303 insertions, 0 deletions

diff --git a/crates/completion/src/render/function.rs b/crates/completion/src/render/function.rs
new file mode 100644
index 000000000..4fa6eafd7
--- /dev/null
+++ b/crates/completion/src/render/function.rs
@@ -0,0 +1,303 @@
+//! Renderer for function calls.
+
+use hir::{HasSource, Type};
+use syntax::{ast::Fn, display::function_declaration};
+
+use crate::{
+    item::{CompletionItem, CompletionItemKind, CompletionKind},
+    render::{builder_ext::Params, RenderContext},
+};
+
+pub(crate) fn render_fn<'a>(
+    ctx: RenderContext<'a>,
+    local_name: Option<String>,
+    fn_: hir::Function,
+) -> CompletionItem {
+    FunctionRender::new(ctx, local_name, fn_).render()
+}
+
+#[derive(Debug)]
+struct FunctionRender<'a> {
+    ctx: RenderContext<'a>,
+    name: String,
+    fn_: hir::Function,
+    ast_node: Fn,
+}
+
+impl<'a> FunctionRender<'a> {
+    fn new(
+        ctx: RenderContext<'a>,
+        local_name: Option<String>,
+        fn_: hir::Function,
+    ) -> FunctionRender<'a> {
+        let name = local_name.unwrap_or_else(|| fn_.name(ctx.db()).to_string());
+        let ast_node = fn_.source(ctx.db()).value;
+
+        FunctionRender { ctx, name, fn_, ast_node }
+    }
+
+    fn render(self) -> CompletionItem {
+        let params = self.params();
+        CompletionItem::new(CompletionKind::Reference, self.ctx.source_range(), self.name.clone())
+            .kind(self.kind())
+            .set_documentation(self.ctx.docs(self.fn_))
+            .set_deprecated(self.ctx.is_deprecated(self.fn_))
+            .detail(self.detail())
+            .add_call_parens(self.ctx.completion, self.name, params)
+            .build()
+    }
+
+    fn detail(&self) -> String {
+        function_declaration(&self.ast_node)
+    }
+
+    fn add_arg(&self, arg: &str, ty: &Type) -> String {
+        if let Some(derefed_ty) = ty.remove_ref() {
+            for (name, local) in self.ctx.completion.locals.iter() {
+                if name == arg && local.ty(self.ctx.db()) == derefed_ty {
+                    let mutability = if ty.is_mutable_reference() { "&mut " } else { "&" };
+                    return format!("{}{}", mutability, arg);
+                }
+            }
+        }
+        arg.to_string()
+    }
+
+    fn params(&self) -> Params {
+        let params_ty = self.fn_.params(self.ctx.db());
+        let params = self
+            .ast_node
+            .param_list()
+            .into_iter()
+            .flat_map(|it| it.params())
+            .zip(params_ty)
+            .flat_map(|(it, param_ty)| {
+                if let Some(pat) = it.pat() {
+                    let name = pat.to_string();
+                    let arg = name.trim_start_matches("mut ").trim_start_matches('_');
+                    return Some(self.add_arg(arg, param_ty.ty()));
+                }
+                None
+            })
+            .collect();
+        Params::Named(params)
+    }
+
+    fn kind(&self) -> CompletionItemKind {
+        if self.fn_.self_param(self.ctx.db()).is_some() {
+            CompletionItemKind::Method
+        } else {
+            CompletionItemKind::Function
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::mark;
+
+    use crate::{
+        test_utils::{check_edit, check_edit_with_config},
+        CompletionConfig,
+    };
+
+    #[test]
+    fn inserts_parens_for_function_calls() {
+        mark::check!(inserts_parens_for_function_calls);
+        check_edit(
+            "no_args",
+            r#"
+fn no_args() {}
+fn main() { no_<|> }
+"#,
+            r#"
+fn no_args() {}
+fn main() { no_args()$0 }
+"#,
+        );
+
+        check_edit(
+            "with_args",
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_<|> }
+"#,
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_args(${1:x}, ${2:y})$0 }
+"#,
+        );
+
+        check_edit(
+            "foo",
+            r#"
+struct S;
+impl S {
+    fn foo(&self) {}
+}
+fn bar(s: &S) { s.f<|> }
+"#,
+            r#"
+struct S;
+impl S {
+    fn foo(&self) {}
+}
+fn bar(s: &S) { s.foo()$0 }
+"#,
+        );
+
+        check_edit(
+            "foo",
+            r#"
+struct S {}
+impl S {
+    fn foo(&self, x: i32) {}
+}
+fn bar(s: &S) {
+    s.f<|>
+}
+"#,
+            r#"
+struct S {}
+impl S {
+    fn foo(&self, x: i32) {}
+}
+fn bar(s: &S) {
+    s.foo(${1:x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn suppress_arg_snippets() {
+        mark::check!(suppress_arg_snippets);
+        check_edit_with_config(
+            CompletionConfig { add_call_argument_snippets: false, ..CompletionConfig::default() },
+            "with_args",
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_<|> }
+"#,
+            r#"
+fn with_args(x: i32, y: String) {}
+fn main() { with_args($0) }
+"#,
+        );
+    }
+
+    #[test]
+    fn strips_underscores_from_args() {
+        check_edit(
+            "foo",
+            r#"
+fn foo(_foo: i32, ___bar: bool, ho_ge_: String) {}
+fn main() { f<|> }
+"#,
+            r#"
+fn foo(_foo: i32, ___bar: bool, ho_ge_: String) {}
+fn main() { foo(${1:foo}, ${2:bar}, ${3:ho_ge_})$0 }
+"#,
+        );
+    }
+
+    #[test]
+    fn insert_ref_when_matching_local_in_scope() {
+        check_edit(
+            "ref_arg",
+            r#"
+struct Foo {}
+fn ref_arg(x: &Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_ar<|>
+}
+"#,
+            r#"
+struct Foo {}
+fn ref_arg(x: &Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_arg(${1:&x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn insert_mut_ref_when_matching_local_in_scope() {
+        check_edit(
+            "ref_arg",
+            r#"
+struct Foo {}
+fn ref_arg(x: &mut Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_ar<|>
+}
+"#,
+            r#"
+struct Foo {}
+fn ref_arg(x: &mut Foo) {}
+fn main() {
+    let x = Foo {};
+    ref_arg(${1:&mut x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn insert_ref_when_matching_local_in_scope_for_method() {
+        check_edit(
+            "apply_foo",
+            r#"
+struct Foo {}
+struct Bar {}
+impl Bar {
+    fn apply_foo(&self, x: &Foo) {}
+}
+
+fn main() {
+    let x = Foo {};
+    let y = Bar {};
+    y.<|>
+}
+"#,
+            r#"
+struct Foo {}
+struct Bar {}
+impl Bar {
+    fn apply_foo(&self, x: &Foo) {}
+}
+
+fn main() {
+    let x = Foo {};
+    let y = Bar {};
+    y.apply_foo(${1:&x})$0
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn trim_mut_keyword_in_func_completion() {
+        check_edit(
+            "take_mutably",
+            r#"
+fn take_mutably(mut x: &i32) {}
+
+fn main() {
+    take_m<|>
+}
+"#,
+            r#"
+fn take_mutably(mut x: &i32) {}
+
+fn main() {
+    take_mutably(${1:x})$0
+}
+"#,
+        );
+    }
+}