assist to convert if-let to match

1 files changed, 92 insertions, 0 deletions

diff --git a/crates/ra_editor/src/assists/replace_if_let_with_match.rs b/crates/ra_editor/src/assists/replace_if_let_with_match.rs
new file mode 100644
index 000000000..30c371480
--- /dev/null
+++ b/crates/ra_editor/src/assists/replace_if_let_with_match.rs
@@ -0,0 +1,92 @@
+use ra_syntax::{
+    AstNode, SyntaxKind::{L_CURLY, R_CURLY, WHITESPACE},
+    ast,
+};
+
+use crate::assists::{AssistCtx, Assist};
+
+pub fn replace_if_let_with_match(ctx: AssistCtx) -> Option<Assist> {
+    let if_expr: &ast::IfExpr = ctx.node_at_offset()?;
+    let cond = if_expr.condition()?;
+    let pat = cond.pat()?;
+    let expr = cond.expr()?;
+    let then_block = if_expr.then_branch()?;
+    let else_block = if_expr.else_branch()?;
+
+    ctx.build("replace with match", |edit| {
+        let match_expr = build_match_expr(expr, pat, then_block, else_block);
+        edit.replace_node_and_indent(if_expr.syntax(), match_expr);
+        edit.set_cursor(if_expr.syntax().range().start())
+    })
+}
+
+fn build_match_expr(
+    expr: &ast::Expr,
+    pat1: &ast::Pat,
+    arm1: &ast::Block,
+    arm2: &ast::Block,
+) -> String {
+    let mut buf = String::new();
+    buf.push_str(&format!("match {} {{\n", expr.syntax().text()));
+    buf.push_str(&format!(
+        "    {} => {}\n",
+        pat1.syntax().text(),
+        format_arm(arm1)
+    ));
+    buf.push_str(&format!("    _ => {}\n", format_arm(arm2)));
+    buf.push_str("}");
+    buf
+}
+
+fn format_arm(block: &ast::Block) -> String {
+    match extract_expression(block) {
+        None => block.syntax().text().to_string(),
+        Some(e) => format!("{},", e.syntax().text()),
+    }
+}
+
+fn extract_expression(block: &ast::Block) -> Option<&ast::Expr> {
+    let expr = block.expr()?;
+    let non_trivial_children = block.syntax().children().filter(|it| {
+        !(it == &expr.syntax()
+            || it.kind() == L_CURLY
+            || it.kind() == R_CURLY
+            || it.kind() == WHITESPACE)
+    });
+    if non_trivial_children.count() > 0 {
+        return None;
+    }
+    Some(expr)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::assists::check_assist;
+
+    #[test]
+    fn test_replace_if_let_with_match_unwraps_simple_expressions() {
+        check_assist(
+            replace_if_let_with_match,
+            "
+impl VariantData {
+    pub fn is_struct(&self) -> bool {
+        if <|>let VariantData::Struct(..) = *self {
+            true
+        } else {
+            false
+        }
+    }
+}           ",
+            "
+impl VariantData {
+    pub fn is_struct(&self) -> bool {
+        <|>match *self {
+            VariantData::Struct(..) => true,
+            _ => false,
+        }
+    }
+}           ",
+        )
+    }
+}