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use ra_syntax::ast::{self, AstNode};
use crate::{utils::invert_boolean_expression, 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 = op_range.contains_range(ctx.frange.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 }")
}
}
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