From 561b4b11ff1d87ea1ff2477dcba6ae1f396573a3 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Fri, 7 Feb 2020 15:53:31 +0100
Subject: Name assist handlers

---
 crates/ra_assists/src/handlers/apply_demorgan.rs | 90 ++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 crates/ra_assists/src/handlers/apply_demorgan.rs

(limited to 'crates/ra_assists/src/handlers/apply_demorgan.rs')

diff --git a/crates/ra_assists/src/handlers/apply_demorgan.rs b/crates/ra_assists/src/handlers/apply_demorgan.rs
new file mode 100644
index 000000000..ba08a8223
--- /dev/null
+++ b/crates/ra_assists/src/handlers/apply_demorgan.rs
@@ -0,0 +1,90 @@
+use super::invert_if::invert_boolean_expression;
+use ra_syntax::ast::{self, AstNode};
+
+use crate::{Assist, AssistCtx, AssistId};
+
+// Assist: apply_demorgan
+//
+// Apply [De Morgan's law](https://en.wikipedia.org/wiki/De_Morgan%27s_laws).
+// This transforms expressions of the form `!l || !r` into `!(l && r)`.
+// This also works with `&&`. This assist can only be applied with the cursor
+// on either `||` or `&&`, with both operands being a negation of some kind.
+// This means something of the form `!x` or `x != y`.
+//
+// ```
+// fn main() {
+//     if x != 4 ||<|> !y {}
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     if !(x == 4 && y) {}
+// }
+// ```
+pub(crate) fn apply_demorgan(ctx: AssistCtx) -> Option<Assist> {
+    let expr = ctx.find_node_at_offset::<ast::BinExpr>()?;
+    let op = expr.op_kind()?;
+    let op_range = expr.op_token()?.text_range();
+    let opposite_op = opposite_logic_op(op)?;
+    let cursor_in_range = ctx.frange.range.is_subrange(&op_range);
+    if !cursor_in_range {
+        return None;
+    }
+
+    let lhs = expr.lhs()?;
+    let lhs_range = lhs.syntax().text_range();
+    let not_lhs = invert_boolean_expression(lhs);
+
+    let rhs = expr.rhs()?;
+    let rhs_range = rhs.syntax().text_range();
+    let not_rhs = invert_boolean_expression(rhs);
+
+    ctx.add_assist(AssistId("apply_demorgan"), "Apply De Morgan's law", |edit| {
+        edit.target(op_range);
+        edit.replace(op_range, opposite_op);
+        edit.replace(lhs_range, format!("!({}", not_lhs.syntax().text()));
+        edit.replace(rhs_range, format!("{})", not_rhs.syntax().text()));
+    })
+}
+
+// Return the opposite text for a given logical operator, if it makes sense
+fn opposite_logic_op(kind: ast::BinOp) -> Option<&'static str> {
+    match kind {
+        ast::BinOp::BooleanOr => Some("&&"),
+        ast::BinOp::BooleanAnd => Some("||"),
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn demorgan_turns_and_into_or() {
+        check_assist(apply_demorgan, "fn f() { !x &&<|> !x }", "fn f() { !(x ||<|> x) }")
+    }
+
+    #[test]
+    fn demorgan_turns_or_into_and() {
+        check_assist(apply_demorgan, "fn f() { !x ||<|> !x }", "fn f() { !(x &&<|> x) }")
+    }
+
+    #[test]
+    fn demorgan_removes_inequality() {
+        check_assist(apply_demorgan, "fn f() { x != x ||<|> !x }", "fn f() { !(x == x &&<|> x) }")
+    }
+
+    #[test]
+    fn demorgan_general_case() {
+        check_assist(apply_demorgan, "fn f() { x ||<|> x }", "fn f() { !(!x &&<|> !x) }")
+    }
+
+    #[test]
+    fn demorgan_doesnt_apply_with_cursor_not_on_op() {
+        check_assist_not_applicable(apply_demorgan, "fn f() { <|> !x || !x }")
+    }
+}
-- 
cgit v1.2.3


From d00add1f1fec59494c3c1a99c27937ae3891458d Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Fri, 7 Feb 2020 15:57:38 +0100
Subject: Introduce assists utils

---
 crates/ra_assists/src/handlers/apply_demorgan.rs | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

(limited to 'crates/ra_assists/src/handlers/apply_demorgan.rs')

diff --git a/crates/ra_assists/src/handlers/apply_demorgan.rs b/crates/ra_assists/src/handlers/apply_demorgan.rs
index ba08a8223..239807e24 100644
--- a/crates/ra_assists/src/handlers/apply_demorgan.rs
+++ b/crates/ra_assists/src/handlers/apply_demorgan.rs
@@ -1,7 +1,6 @@
-use super::invert_if::invert_boolean_expression;
 use ra_syntax::ast::{self, AstNode};
 
-use crate::{Assist, AssistCtx, AssistId};
+use crate::{utils::invert_boolean_expression, Assist, AssistCtx, AssistId};
 
 // Assist: apply_demorgan
 //
-- 
cgit v1.2.3