bendns' repos / rust-analyzer
Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/ide-assists/src/handlers/convert_nested_function_to_closure.rs')
-rw-r--r--crates/ide-assists/src/handlers/convert_nested_function_to_closure.rs185
1 files changed, 185 insertions, 0 deletions
diff --git a/crates/ide-assists/src/handlers/convert_nested_function_to_closure.rs b/crates/ide-assists/src/handlers/convert_nested_function_to_closure.rs
new file mode 100644
index 0000000000..0524c27890
--- /dev/null
+++ b/crates/ide-assists/src/handlers/convert_nested_function_to_closure.rs
@@ -0,0 +1,185 @@
+use ide_db::assists::{AssistId, AssistKind};
+use syntax::ast::{self, HasGenericParams, HasName};
+use syntax::{AstNode, SyntaxKind};
+
+use crate::assist_context::{AssistContext, Assists};
+
+// Assist: convert_nested_function_to_closure
+//
+// Converts a function that is defined within the body of another function into a closure.
+//
+// ```
+// fn main() {
+// fn fo$0o(label: &str, number: u64) {
+// println!("{}: {}", label, number);
+// }
+//
+// foo("Bar", 100);
+// }
+// ```
+// ->
+// ```
+// fn main() {
+// let foo = |label: &str, number: u64| {
+// println!("{}: {}", label, number);
+// };
+//
+// foo("Bar", 100);
+// }
+// ```
+pub(crate) fn convert_nested_function_to_closure(
+ acc: &mut Assists,
+ ctx: &AssistContext<'_>,
+) -> Option<()> {
+ let name = ctx.find_node_at_offset::<ast::Name>()?;
+ let function = name.syntax().parent().and_then(ast::Fn::cast)?;
+
+ if !is_nested_function(&function) || is_generic(&function) {
+ return None;
+ }
+
+ let target = function.syntax().text_range();
+ let body = function.body()?;
+ let name = function.name()?;
+ let params = function.param_list()?;
+
+ acc.add(
+ AssistId("convert_nested_function_to_closure", AssistKind::RefactorRewrite),
+ "Convert nested function to closure",
+ target,
+ |edit| {
+ let has_semicolon = has_semicolon(&function);
+ let params_text = params.syntax().text().to_string();
+ let params_text_trimmed =
+ params_text.strip_prefix("(").and_then(|p| p.strip_suffix(")"));
+
+ if let Some(closure_params) = params_text_trimmed {
+ let body = body.to_string();
+ let body = if has_semicolon { body } else { format!("{};", body) };
+ edit.replace(target, format!("let {} = |{}| {}", name, closure_params, body));
+ }
+ },
+ )
+}
+
+/// Returns whether the given function is nested within the body of another function.
+fn is_nested_function(function: &ast::Fn) -> bool {
+ function
+ .syntax()
+ .parent()
+ .map(|p| p.ancestors().any(|a| a.kind() == SyntaxKind::FN))
+ .unwrap_or(false)
+}
+
+/// Returns whether the given nested function has generic parameters.
+fn is_generic(function: &ast::Fn) -> bool {
+ function.generic_param_list().is_some()
+}
+
+/// Returns whether the given nested function has a trailing semicolon.
+fn has_semicolon(function: &ast::Fn) -> bool {
+ function
+ .syntax()
+ .next_sibling_or_token()
+ .map(|t| t.kind() == SyntaxKind::SEMICOLON)
+ .unwrap_or(false)
+}
+
+#[cfg(test)]
+mod tests {
+ use crate::tests::{check_assist, check_assist_not_applicable};
+
+ use super::convert_nested_function_to_closure;
+
+ #[test]
+ fn convert_nested_function_to_closure_works() {
+ check_assist(
+ convert_nested_function_to_closure,
+ r#"
+fn main() {
+ fn $0foo(a: u64, b: u64) -> u64 {
+ 2 * (a + b)
+ }
+
+ _ = foo(3, 4);
+}
+ "#,
+ r#"
+fn main() {
+ let foo = |a: u64, b: u64| {
+ 2 * (a + b)
+ };
+
+ _ = foo(3, 4);
+}
+ "#,
+ );
+ }
+
+ #[test]
+ fn convert_nested_function_to_closure_works_with_existing_semicolon() {
+ check_assist(
+ convert_nested_function_to_closure,
+ r#"
+fn main() {
+ fn foo$0(a: u64, b: u64) -> u64 {
+ 2 * (a + b)
+ };
+
+ _ = foo(3, 4);
+}
+ "#,
+ r#"
+fn main() {
+ let foo = |a: u64, b: u64| {
+ 2 * (a + b)
+ };
+
+ _ = foo(3, 4);
+}
+ "#,
+ );
+ }
+
+ #[test]
+ fn convert_nested_function_to_closure_does_not_work_on_top_level_function() {
+ check_assist_not_applicable(
+ convert_nested_function_to_closure,
+ r#"
+fn ma$0in() {}
+ "#,
+ );
+ }
+
+ #[test]
+ fn convert_nested_function_to_closure_does_not_work_when_cursor_off_name() {
+ check_assist_not_applicable(
+ convert_nested_function_to_closure,
+ r#"
+fn main() {
+ fn foo(a: u64, $0b: u64) -> u64 {
+ 2 * (a + b)
+ };
+
+ _ = foo(3, 4);
+}
+ "#,
+ );
+ }
+
+ #[test]
+ fn convert_nested_function_to_closure_does_not_work_if_function_has_generic_params() {
+ check_assist_not_applicable(
+ convert_nested_function_to_closure,
+ r#"
+fn main() {
+ fn fo$0o<S: Into<String>>(s: S) -> String {
+ s.into()
+ };
+
+ _ = foo("hello");
+}
+ "#,
+ );
+ }
+}