From 9ecf6684526a0f82476234ee8feea56a442f6c0e Mon Sep 17 00:00:00 2001
From: Vincent Ambo <mail@tazj.in>
Date: Mon, 23 Jan 2023 20:28:53 +0300
Subject: chore(tvix/eval): delete "useless parenthesis" warning/optimisation

Two main reasons:

1. Traversing the structure to do this optimisation is
   actually *slower* than not optimising it.

2. There are literally hundreds of thousands of incidences of this in
   nixpkgs, and with some of the weird code there some of
   these (functionally) useless parens are actually required for
   readability reasons.

Change-Id: I1044b1c5f9fe20df4b6085851fc3b191277c65dc
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7917
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>
---
 tvix/eval/src/compiler/optimiser.rs | 26 --------------------------
 tvix/eval/src/warnings.rs           |  4 ----
 2 files changed, 30 deletions(-)

(limited to 'tvix/eval')

diff --git a/tvix/eval/src/compiler/optimiser.rs b/tvix/eval/src/compiler/optimiser.rs
index ace5335d6835..4c28b79a851e 100644
--- a/tvix/eval/src/compiler/optimiser.rs
+++ b/tvix/eval/src/compiler/optimiser.rs
@@ -9,7 +9,6 @@ use ast::Expr;
 pub(super) fn optimise_expr(c: &mut Compiler, slot: LocalIdx, expr: ast::Expr) -> ast::Expr {
     match expr {
         Expr::BinOp(_) => optimise_bin_op(c, slot, expr),
-        Expr::Paren(_) => optimise_paren(c, expr),
         _ => expr.to_owned(),
     }
 }
@@ -124,28 +123,3 @@ fn optimise_bin_op(c: &mut Compiler, slot: LocalIdx, expr: ast::Expr) -> ast::Ex
 
     expr
 }
-
-/// Detect useless parenthesis around primitive expressions.
-fn optimise_paren(c: &mut Compiler, expr: ast::Expr) -> ast::Expr {
-    if let Expr::Paren(inner) = &expr {
-        let inner = inner.expr().unwrap();
-
-        if let Expr::Paren(_) = &inner {
-            c.emit_warning(&expr, WarningKind::UselessParens);
-            return optimise_paren(c, inner);
-        }
-
-        if let Expr::Literal(_)
-        | Expr::Str(_)
-        | Expr::Select(_)
-        | Expr::List(_)
-        | Expr::AttrSet(_)
-        | Expr::Ident(_) = &inner
-        {
-            c.emit_warning(&expr, WarningKind::UselessParens);
-            return inner;
-        }
-    }
-
-    expr
-}
diff --git a/tvix/eval/src/warnings.rs b/tvix/eval/src/warnings.rs
index 5395fc20b9c8..aa567f302755 100644
--- a/tvix/eval/src/warnings.rs
+++ b/tvix/eval/src/warnings.rs
@@ -17,7 +17,6 @@ pub enum WarningKind {
     DeadCode,
     EmptyInherit,
     EmptyLet,
-    UselessParens,
 
     /// Tvix internal warning for features triggered by users that are
     /// not actually implemented yet, but do not cause runtime failures.
@@ -101,8 +100,6 @@ impl EvalWarning {
 
             WarningKind::EmptyLet => "this `let`-expression contains no bindings".to_string(),
 
-            WarningKind::UselessParens => "these parenthesis can be removed".to_string(),
-
             WarningKind::NotImplemented(what) => {
                 format!("feature not yet implemented in tvix: {}", what)
             }
@@ -123,7 +120,6 @@ impl EvalWarning {
             WarningKind::DeadCode => "W008",
             WarningKind::EmptyInherit => "W009",
             WarningKind::EmptyLet => "W010",
-            WarningKind::UselessParens => "W011",
 
             WarningKind::NotImplemented(_) => "W999",
         }
-- 
cgit 1.4.1