use hir::db::HirDatabase; use ra_syntax::ast::{self, AstNode}; use ra_syntax::SyntaxNode; 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 { let expr = ctx.find_node_at_offset::()?; 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()?.syntax().clone(); let lhs_range = lhs.text_range(); let rhs = expr.rhs()?.syntax().clone(); let rhs_range = rhs.text_range(); let not_lhs = undo_negation(lhs)?; let not_rhs = undo_negation(rhs)?; ctx.add_assist(AssistId("apply_demorgan"), "apply demorgan's law", |edit| { edit.target(op_range); edit.replace(op_range, opposite_op); edit.replace(lhs_range, format!("!({}", not_lhs)); edit.replace(rhs_range, format!("{})", not_rhs)); }) } // 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, } } // This function tries to undo unary negation, or inequality fn undo_negation(node: SyntaxNode) -> Option { match ast::Expr::cast(node)? { ast::Expr::BinExpr(bin) => match bin.op_kind()? { ast::BinOp::NegatedEqualityTest => { let lhs = bin.lhs()?.syntax().text(); let rhs = bin.rhs()?.syntax().text(); Some(format!("{} == {}", lhs, rhs)) } _ => None, }, ast::Expr::PrefixExpr(pe) => match pe.op_kind()? { ast::PrefixOp::Not => { let child = pe.expr()?.syntax().text(); Some(String::from(child)) } _ => None, }, _ => 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_doesnt_apply_with_cursor_not_on_op() { check_assist_not_applicable(apply_demorgan, "fn f() { <|> !x || !x }") } #[test] fn demorgan_doesnt_apply_when_operands_arent_negated_already() { check_assist_not_applicable(apply_demorgan, "fn f() { x ||<|> x }") } }