94 lines
2.7 KiB
Rust
94 lines
2.7 KiB
Rust
use ra_syntax::ast::{self, AstNode};
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use crate::{utils::invert_boolean_expression, AssistContext, AssistId, AssistKind, Assists};
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// Assist: apply_demorgan
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//
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// Apply [De Morgan's law](https://en.wikipedia.org/wiki/De_Morgan%27s_laws).
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// This transforms expressions of the form `!l || !r` into `!(l && r)`.
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// This also works with `&&`. This assist can only be applied with the cursor
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// on either `||` or `&&`, with both operands being a negation of some kind.
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// This means something of the form `!x` or `x != y`.
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//
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// ```
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// fn main() {
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// if x != 4 ||<|> !y {}
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// }
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// ```
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// ->
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// ```
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// fn main() {
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// if !(x == 4 && y) {}
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// }
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// ```
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pub(crate) fn apply_demorgan(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
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let expr = ctx.find_node_at_offset::<ast::BinExpr>()?;
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let op = expr.op_kind()?;
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let op_range = expr.op_token()?.text_range();
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let opposite_op = opposite_logic_op(op)?;
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let cursor_in_range = op_range.contains_range(ctx.frange.range);
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if !cursor_in_range {
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return None;
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}
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let lhs = expr.lhs()?;
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let lhs_range = lhs.syntax().text_range();
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let not_lhs = invert_boolean_expression(lhs);
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let rhs = expr.rhs()?;
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let rhs_range = rhs.syntax().text_range();
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let not_rhs = invert_boolean_expression(rhs);
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acc.add(
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AssistId("apply_demorgan", AssistKind::RefactorRewrite),
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"Apply De Morgan's law",
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op_range,
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|edit| {
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edit.replace(op_range, opposite_op);
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edit.replace(lhs_range, format!("!({}", not_lhs.syntax().text()));
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edit.replace(rhs_range, format!("{})", not_rhs.syntax().text()));
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},
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)
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}
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// Return the opposite text for a given logical operator, if it makes sense
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fn opposite_logic_op(kind: ast::BinOp) -> Option<&'static str> {
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match kind {
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ast::BinOp::BooleanOr => Some("&&"),
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ast::BinOp::BooleanAnd => Some("||"),
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_ => None,
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use crate::tests::{check_assist, check_assist_not_applicable};
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#[test]
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fn demorgan_turns_and_into_or() {
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check_assist(apply_demorgan, "fn f() { !x &&<|> !x }", "fn f() { !(x || x) }")
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}
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#[test]
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fn demorgan_turns_or_into_and() {
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check_assist(apply_demorgan, "fn f() { !x ||<|> !x }", "fn f() { !(x && x) }")
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}
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#[test]
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fn demorgan_removes_inequality() {
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check_assist(apply_demorgan, "fn f() { x != x ||<|> !x }", "fn f() { !(x == x && x) }")
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}
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#[test]
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fn demorgan_general_case() {
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check_assist(apply_demorgan, "fn f() { x ||<|> x }", "fn f() { !(!x && !x) }")
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}
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#[test]
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fn demorgan_doesnt_apply_with_cursor_not_on_op() {
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check_assist_not_applicable(apply_demorgan, "fn f() { <|> !x || !x }")
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}
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}
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