diff --git a/CHANGELOG.md b/CHANGELOG.md
index 559b560dde4b..0fb96b266c7e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4967,6 +4967,7 @@ Released 2018-09-13
[`try_err`]: https://rust-lang.github.io/rust-clippy/master/index.html#try_err
[`type_complexity`]: https://rust-lang.github.io/rust-clippy/master/index.html#type_complexity
[`type_repetition_in_bounds`]: https://rust-lang.github.io/rust-clippy/master/index.html#type_repetition_in_bounds
+[`unary_parenthesis_followed_by_cast`]: https://rust-lang.github.io/rust-clippy/master/index.html#unary_parenthesis_followed_by_cast
[`unchecked_duration_subtraction`]: https://rust-lang.github.io/rust-clippy/master/index.html#unchecked_duration_subtraction
[`undocumented_unsafe_blocks`]: https://rust-lang.github.io/rust-clippy/master/index.html#undocumented_unsafe_blocks
[`undropped_manually_drops`]: https://rust-lang.github.io/rust-clippy/master/index.html#undropped_manually_drops
diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs
index f24dab627809..61e3c80d2cf2 100644
--- a/clippy_lints/src/declared_lints.rs
+++ b/clippy_lints/src/declared_lints.rs
@@ -610,6 +610,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
crate::types::REDUNDANT_ALLOCATION_INFO,
crate::types::TYPE_COMPLEXITY_INFO,
crate::types::VEC_BOX_INFO,
+ crate::unary_parenthesis_followed_by_cast::UNARY_PARENTHESIS_FOLLOWED_BY_CAST_INFO,
crate::undocumented_unsafe_blocks::UNDOCUMENTED_UNSAFE_BLOCKS_INFO,
crate::undocumented_unsafe_blocks::UNNECESSARY_SAFETY_COMMENT_INFO,
crate::unicode::INVISIBLE_CHARACTERS_INFO,
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index bac82eca8174..0180c37e7b7b 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -298,6 +298,7 @@ mod trailing_empty_array;
mod trait_bounds;
mod transmute;
mod types;
+mod unary_parenthesis_followed_by_cast;
mod undocumented_unsafe_blocks;
mod unicode;
mod uninit_vec;
@@ -960,6 +961,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
store.register_late_pass(|_| Box::new(tests_outside_test_module::TestsOutsideTestModule));
store.register_late_pass(|_| Box::new(manual_slice_size_calculation::ManualSliceSizeCalculation));
store.register_early_pass(|| Box::new(suspicious_doc_comments::SuspiciousDocComments));
+ store.register_early_pass(|| Box::new(unary_parenthesis_followed_by_cast::UnaryParenthesisFollowedByCast));
// add lints here, do not remove this comment, it's used in `new_lint`
}
diff --git a/clippy_lints/src/unary_parenthesis_followed_by_cast.rs b/clippy_lints/src/unary_parenthesis_followed_by_cast.rs
new file mode 100644
index 000000000000..52ca6a965107
--- /dev/null
+++ b/clippy_lints/src/unary_parenthesis_followed_by_cast.rs
@@ -0,0 +1,67 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use rustc_ast::ast::{Expr, ExprKind, Path};
+use rustc_ast::ast_traits::AstDeref;
+use rustc_ast::ptr::P;
+use rustc_lint::{EarlyContext, EarlyLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for cast which argument is parenthesized variable.
+ ///
+ /// ### Why is this bad?
+ /// It's same effect as `variable as Type`, thus you don't need parentheses.
+ ///
+ /// ### Example
+ /// ```rust
+ /// fn no_op(arg_1: f64) {}
+ ///
+ /// let x = (1.0f32) as f64;
+ /// let y = (2.0f32) as f64;
+ /// no_op(y);
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// fn no_op(arg_1: f64) {}
+ ///
+ /// let x = 1.0f32 as f64;
+ /// let y = 2.0f32 as f64;
+ /// no_op(y);
+ /// ```
+ #[clippy::version = "1.70.0"]
+ pub UNARY_PARENTHESIS_FOLLOWED_BY_CAST,
+ complexity,
+ "`as` cast with parenthesized simple argument"
+}
+declare_lint_pass!(UnaryParenthesisFollowedByCast => [UNARY_PARENTHESIS_FOLLOWED_BY_CAST]);
+
+impl EarlyLintPass for UnaryParenthesisFollowedByCast {
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
+ if let ExprKind::Cast(ref expr, _) = expr.kind
+ && let ExprKind::Paren(ref parenthesized) = expr.kind
+ && is_item_path_is_local_and_not_qualified(parenthesized)
+ {
+ span_lint_and_help(
+ cx,
+ UNARY_PARENTHESIS_FOLLOWED_BY_CAST,
+ expr.span,
+ "unnecessary parenthesis",
+ None,
+ "consider remove parenthesis"
+ );
+ }
+ }
+}
+
+fn is_item_path_is_local_and_not_qualified(parenthesized: &P<Expr>) -> bool {
+ if let ExprKind::Path(ref impl_qualifier, ref item_path) = parenthesized.ast_deref().kind
+ && impl_qualifier.is_none()
+ // is item_path local variable?
+ && !item_path.is_global()
+ && let Path { segments, .. } = item_path
+ && segments.len() == 1 {
+ true
+ } else {
+ false
+ }
+}
diff --git a/tests/ui/unary_parenthesis_followed_by_cast.rs b/tests/ui/unary_parenthesis_followed_by_cast.rs
new file mode 100644
index 000000000000..1e7dc367ca52
--- /dev/null
+++ b/tests/ui/unary_parenthesis_followed_by_cast.rs
@@ -0,0 +1,12 @@
+#![allow(unused)]
+#![allow(clippy::unnecessary_cast)]
+#![warn(clippy::unary_parenthesis_followed_by_cast)]
+
+fn hello(arg_1: f64) {}
+
+fn main() {
+ // fire
+ let x = 3.0f32;
+
+ hello((x) as f64);
+}
diff --git a/tests/ui/unary_parenthesis_followed_by_cast.stderr b/tests/ui/unary_parenthesis_followed_by_cast.stderr
new file mode 100644
index 000000000000..3096e614b85e
--- /dev/null
+++ b/tests/ui/unary_parenthesis_followed_by_cast.stderr
@@ -0,0 +1,11 @@
+error: unnecessary parenthesis
+ --> $DIR/unary_parenthesis_followed_by_cast.rs:11:11
+ |
+LL | hello((x) as f64);
+ | ^^^
+ |
+ = help: consider remove parenthesis
+ = note: `-D clippy::unary-parenthesis-followed-by-cast` implied by `-D warnings`
+
+error: aborting due to previous error
+