1 files changed, 148 insertions, 0 deletions

diff --git a/crates/ra_assists/src/handlers/replace_if_let_with_match.rs b/crates/ra_assists/src/handlers/replace_if_let_with_match.rs
new file mode 100644
index 000000000..e6cd50bc1
--- /dev/null
+++ b/crates/ra_assists/src/handlers/replace_if_let_with_match.rs
@@ -0,0 +1,148 @@
+use ra_fmt::unwrap_trivial_block;
+use ra_syntax::{
+    ast::{self, make},
+    AstNode,
+};
+
+use crate::{Assist, AssistCtx, AssistId};
+use ast::edit::IndentLevel;
+
+// Assist: replace_if_let_with_match
+//
+// Replaces `if let` with an else branch with a `match` expression.
+//
+// ```
+// enum Action { Move { distance: u32 }, Stop }
+//
+// fn handle(action: Action) {
+//     <|>if let Action::Move { distance } = action {
+//         foo(distance)
+//     } else {
+//         bar()
+//     }
+// }
+// ```
+// ->
+// ```
+// enum Action { Move { distance: u32 }, Stop }
+//
+// fn handle(action: Action) {
+//     match action {
+//         Action::Move { distance } => foo(distance),
+//         _ => bar(),
+//     }
+// }
+// ```
+pub(crate) fn replace_if_let_with_match(ctx: AssistCtx) -> Option<Assist> {
+    let if_expr: ast::IfExpr = ctx.find_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 = match if_expr.else_branch()? {
+        ast::ElseBranch::Block(it) => it,
+        ast::ElseBranch::IfExpr(_) => return None,
+    };
+
+    ctx.add_assist(AssistId("replace_if_let_with_match"), "Replace with match", |edit| {
+        let match_expr = {
+            let then_arm = {
+                let then_expr = unwrap_trivial_block(then_block);
+                make::match_arm(vec![pat], then_expr)
+            };
+            let else_arm = {
+                let else_expr = unwrap_trivial_block(else_block);
+                make::match_arm(vec![make::placeholder_pat().into()], else_expr)
+            };
+            make::expr_match(expr, make::match_arm_list(vec![then_arm, else_arm]))
+        };
+
+        let match_expr = IndentLevel::from_node(if_expr.syntax()).increase_indent(match_expr);
+
+        edit.target(if_expr.syntax().text_range());
+        edit.set_cursor(if_expr.syntax().text_range().start());
+        edit.replace_ast::<ast::Expr>(if_expr.into(), match_expr.into());
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::helpers::{check_assist, check_assist_target};
+
+    #[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,
+        }
+    }
+}           ",
+        )
+    }
+
+    #[test]
+    fn test_replace_if_let_with_match_doesnt_unwrap_multiline_expressions() {
+        check_assist(
+            replace_if_let_with_match,
+            "
+fn foo() {
+    if <|>let VariantData::Struct(..) = a {
+        bar(
+            123
+        )
+    } else {
+        false
+    }
+}           ",
+            "
+fn foo() {
+    <|>match a {
+        VariantData::Struct(..) => {
+            bar(
+                123
+            )
+        }
+        _ => false,
+    }
+}           ",
+        )
+    }
+
+    #[test]
+    fn replace_if_let_with_match_target() {
+        check_assist_target(
+            replace_if_let_with_match,
+            "
+impl VariantData {
+    pub fn is_struct(&self) -> bool {
+        if <|>let VariantData::Struct(..) = *self {
+            true
+        } else {
+            false
+        }
+    }
+}           ",
+            "if let VariantData::Struct(..) = *self {
+            true
+        } else {
+            false
+        }",
+        );
+    }
+}