Introduce assists utils

1 files changed, 27 insertions, 0 deletions

diff --git a/crates/ra_assists/src/utils.rs b/crates/ra_assists/src/utils.rs
new file mode 100644
index 000000000..0d5722295
--- /dev/null
+++ b/crates/ra_assists/src/utils.rs
@@ -0,0 +1,27 @@
+//! Assorted functions shared by several assists.
+
+use ra_syntax::{
+    ast::{self, make},
+    T,
+};
+
+pub(crate) fn invert_boolean_expression(expr: ast::Expr) -> ast::Expr {
+    if let Some(expr) = invert_special_case(&expr) {
+        return expr;
+    }
+    make::expr_prefix(T![!], expr)
+}
+
+fn invert_special_case(expr: &ast::Expr) -> Option<ast::Expr> {
+    match expr {
+        ast::Expr::BinExpr(bin) => match bin.op_kind()? {
+            ast::BinOp::NegatedEqualityTest => bin.replace_op(T![==]).map(|it| it.into()),
+            ast::BinOp::EqualityTest => bin.replace_op(T![!=]).map(|it| it.into()),
+            _ => None,
+        },
+        ast::Expr::PrefixExpr(pe) if pe.op_kind()? == ast::PrefixOp::Not => pe.expr(),
+        // FIXME:
+        // ast::Expr::Literal(true | false )
+        _ => None,
+    }
+}