Auto merge of rust-lang#11853 - J-ZhengLi:issue11814, r=llogiq

expending lint [`blocks_in_if_conditions`] to check match expr as well

closes: rust-lang#11814

changelog: rename lint `blocks_in_if_conditions` to [`blocks_in_conditions`] and expand it to check blocks in match scrutinees

Author: bors

CHANGELOG.md

@@ -4946,6 +4946,7 @@ Released 2018-09-13
 [`blanket_clippy_restriction_lints`]: https://rust-lang.github.io/rust-clippy/master/index.html#blanket_clippy_restriction_lints
 [`block_in_if_condition_expr`]: https://rust-lang.github.io/rust-clippy/master/index.html#block_in_if_condition_expr
 [`block_in_if_condition_stmt`]: https://rust-lang.github.io/rust-clippy/master/index.html#block_in_if_condition_stmt
+[`blocks_in_conditions`]: https://rust-lang.github.io/rust-clippy/master/index.html#blocks_in_conditions
 [`blocks_in_if_conditions`]: https://rust-lang.github.io/rust-clippy/master/index.html#blocks_in_if_conditions
 [`bool_assert_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#bool_assert_comparison
 [`bool_comparison`]: https://rust-lang.github.io/rust-clippy/master/index.html#bool_comparison

clippy_lints/src/blocks_in_conditions.rs

@@ -0,0 +1,137 @@
+use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
+use clippy_utils::source::snippet_block_with_applicability;
+use clippy_utils::ty::implements_trait;
+use clippy_utils::visitors::{for_each_expr, Descend};
+use clippy_utils::{get_parent_expr, higher};
+use core::ops::ControlFlow;
+use rustc_errors::Applicability;
+use rustc_hir::{BlockCheckMode, Expr, ExprKind, MatchSource};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+use rustc_session::declare_lint_pass;
+use rustc_span::sym;
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for `if` conditions that use blocks containing an
+    /// expression, statements or conditions that use closures with blocks.
+    ///
+    /// ### Why is this bad?
+    /// Style, using blocks in the condition makes it hard to read.
+    ///
+    /// ### Examples
+    /// ```no_run
+    /// # fn somefunc() -> bool { true };
+    /// if { true } { /* ... */ }
+    ///
+    /// if { let x = somefunc(); x } { /* ... */ }
+    /// ```
+    ///
+    /// Use instead:
+    /// ```no_run
+    /// # fn somefunc() -> bool { true };
+    /// if true { /* ... */ }
+    ///
+    /// let res = { let x = somefunc(); x };
+    /// if res { /* ... */ }
+    /// ```
+    #[clippy::version = "1.45.0"]
+    pub BLOCKS_IN_CONDITIONS,
+    style,
+    "useless or complex blocks that can be eliminated in conditions"
+}
+
+declare_lint_pass!(BlocksInConditions => [BLOCKS_IN_CONDITIONS]);
+
+const BRACED_EXPR_MESSAGE: &str = "omit braces around single expression condition";
+
+impl<'tcx> LateLintPass<'tcx> for BlocksInConditions {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if in_external_macro(cx.sess(), expr.span) {
+            return;
+        }
+
+        let Some((cond, keyword, desc)) = higher::If::hir(expr)
+            .map(|hif| (hif.cond, "if", "an `if` condition"))
+            .or(if let ExprKind::Match(match_ex, _, MatchSource::Normal) = expr.kind {
+                Some((match_ex, "match", "a `match` scrutinee"))
+            } else {
+                None
+            })
+        else {
+            return;
+        };
+        let complex_block_message = &format!(
+            "in {desc}, avoid complex blocks or closures with blocks; \
+            instead, move the block or closure higher and bind it with a `let`",
+        );
+
+        if let ExprKind::Block(block, _) = &cond.kind {
+            if block.rules == BlockCheckMode::DefaultBlock {
+                if block.stmts.is_empty() {
+                    if let Some(ex) = &block.expr {
+                        // don't dig into the expression here, just suggest that they remove
+                        // the block
+                        if expr.span.from_expansion() || ex.span.from_expansion() {
+                            return;
+                        }
+                        let mut applicability = Applicability::MachineApplicable;
+                        span_lint_and_sugg(
+                            cx,
+                            BLOCKS_IN_CONDITIONS,
+                            cond.span,
+                            BRACED_EXPR_MESSAGE,
+                            "try",
+                            snippet_block_with_applicability(cx, ex.span, "..", Some(expr.span), &mut applicability)
+                                .to_string(),
+                            applicability,
+                        );
+                    }
+                } else {
+                    let span = block.expr.as_ref().map_or_else(|| block.stmts[0].span, |e| e.span);
+                    if span.from_expansion() || expr.span.from_expansion() {
+                        return;
+                    }
+                    // move block higher
+                    let mut applicability = Applicability::MachineApplicable;
+                    span_lint_and_sugg(
+                        cx,
+                        BLOCKS_IN_CONDITIONS,
+                        expr.span.with_hi(cond.span.hi()),
+                        complex_block_message,
+                        "try",
+                        format!(
+                            "let res = {}; {keyword} res",
+                            snippet_block_with_applicability(cx, block.span, "..", Some(expr.span), &mut applicability),
+                        ),
+                        applicability,
+                    );
+                }
+            }
+        } else {
+            let _: Option<!> = for_each_expr(cond, |e| {
+                if let ExprKind::Closure(closure) = e.kind {
+                    // do not lint if the closure is called using an iterator (see #1141)
+                    if let Some(parent) = get_parent_expr(cx, e)
+                        && let ExprKind::MethodCall(_, self_arg, _, _) = &parent.kind
+                        && let caller = cx.typeck_results().expr_ty(self_arg)
+                        && let Some(iter_id) = cx.tcx.get_diagnostic_item(sym::Iterator)
+                        && implements_trait(cx, caller, iter_id, &[])
+                    {
+                        return ControlFlow::Continue(Descend::No);
+                    }
+
+                    let body = cx.tcx.hir().body(closure.body);
+                    let ex = &body.value;
+                    if let ExprKind::Block(block, _) = ex.kind {
+                        if !body.value.span.from_expansion() && !block.stmts.is_empty() {
+                            span_lint(cx, BLOCKS_IN_CONDITIONS, ex.span, complex_block_message);
+                            return ControlFlow::Continue(Descend::No);
+                        }
+                    }
+                }
+                ControlFlow::Continue(Descend::Yes)
+            });
+        }
+    }
+}

clippy_lints/src/blocks_in_if_conditions.rs

@@ -63,7 +63,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::await_holding_invalid::AWAIT_HOLDING_INVALID_TYPE_INFO,
     crate::await_holding_invalid::AWAIT_HOLDING_LOCK_INFO,
     crate::await_holding_invalid::AWAIT_HOLDING_REFCELL_REF_INFO,
-    crate::blocks_in_if_conditions::BLOCKS_IN_IF_CONDITIONS_INFO,
+    crate::blocks_in_conditions::BLOCKS_IN_CONDITIONS_INFO,
     crate::bool_assert_comparison::BOOL_ASSERT_COMPARISON_INFO,
     crate::bool_to_int_with_if::BOOL_TO_INT_WITH_IF_INFO,
     crate::booleans::NONMINIMAL_BOOL_INFO,

clippy_lints/src/declared_lints.rs

@@ -74,7 +74,7 @@ mod assertions_on_result_states;
 mod async_yields_async;
 mod attrs;
 mod await_holding_invalid;
-mod blocks_in_if_conditions;
+mod blocks_in_conditions;
 mod bool_assert_comparison;
 mod bool_to_int_with_if;
 mod booleans;
@@ -654,7 +654,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_late_pass(|_| Box::<significant_drop_tightening::SignificantDropTightening<'_>>::default());
     store.register_late_pass(|_| Box::new(len_zero::LenZero));
     store.register_late_pass(|_| Box::new(attrs::Attributes));
-    store.register_late_pass(|_| Box::new(blocks_in_if_conditions::BlocksInIfConditions));
+    store.register_late_pass(|_| Box::new(blocks_in_conditions::BlocksInConditions));
     store.register_late_pass(|_| Box::new(unicode::Unicode));
     store.register_late_pass(|_| Box::new(uninit_vec::UninitVec));
     store.register_late_pass(|_| Box::new(unit_return_expecting_ord::UnitReturnExpectingOrd));

clippy_lints/src/lib.rs

@@ -4,8 +4,9 @@
 pub static RENAMED_LINTS: &[(&str, &str)] = &[
     ("clippy::almost_complete_letter_range", "clippy::almost_complete_range"),
     ("clippy::blacklisted_name", "clippy::disallowed_names"),
-    ("clippy::block_in_if_condition_expr", "clippy::blocks_in_if_conditions"),
-    ("clippy::block_in_if_condition_stmt", "clippy::blocks_in_if_conditions"),
+    ("clippy::block_in_if_condition_expr", "clippy::blocks_in_conditions"),
+    ("clippy::block_in_if_condition_stmt", "clippy::blocks_in_conditions"),
+    ("clippy::blocks_in_if_conditions", "clippy::blocks_in_conditions"),
     ("clippy::box_vec", "clippy::box_collection"),
     ("clippy::const_static_lifetime", "clippy::redundant_static_lifetimes"),
     ("clippy::cyclomatic_complexity", "clippy::cognitive_complexity"),

clippy_lints/src/renamed_lints.rs

@@ -9,7 +9,7 @@
 #![allow(clippy::never_loop)]
 #![allow(clippy::needless_if)]
 #![warn(clippy::excessive_nesting)]
-#![allow(clippy::collapsible_if)]
+#![allow(clippy::collapsible_if, clippy::blocks_in_conditions)]
 
 #[macro_use]
 extern crate proc_macros;

tests/ui-toml/excessive_nesting/excessive_nesting.rs

@@ -1,5 +1,5 @@
 #![deny(clippy::bind_instead_of_map)]
-#![allow(clippy::blocks_in_if_conditions)]
+#![allow(clippy::blocks_in_conditions)]
 
 pub fn main() {
     let _ = Some("42").map(|s| if s.len() < 42 { 0 } else { s.len() });

tests/ui/bind_instead_of_map_multipart.fixed

@@ -1,5 +1,5 @@
 #![deny(clippy::bind_instead_of_map)]
-#![allow(clippy::blocks_in_if_conditions)]
+#![allow(clippy::blocks_in_conditions)]
 
 pub fn main() {
     let _ = Some("42").and_then(|s| if s.len() < 42 { Some(0) } else { Some(s.len()) });

tests/ui/bind_instead_of_map_multipart.rs

@@ -1,4 +1,4 @@
-#![warn(clippy::blocks_in_if_conditions)]
+#![warn(clippy::blocks_in_conditions)]
 #![allow(unused, clippy::let_and_return, clippy::needless_if)]
 #![warn(clippy::nonminimal_bool)]
 
@@ -21,6 +21,7 @@ fn macro_if() {
 
 fn condition_has_block() -> i32 {
     let res = {
+        //~^ ERROR: in an `if` condition, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a `let`
         let x = 3;
         x == 3
     }; if res {
@@ -32,6 +33,7 @@ fn condition_has_block() -> i32 {
 
 fn condition_has_block_with_single_expression() -> i32 {
     if true { 6 } else { 10 }
+    //~^ ERROR: omit braces around single expression condition
 }
 
 fn condition_is_normal() -> i32 {
@@ -61,4 +63,26 @@ fn block_in_assert() {
     );
 }
 
+// issue #11814
+fn block_in_match_expr(num: i32) -> i32 {
+    let res = {
+        //~^ ERROR: in a `match` scrutinee, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a `let`
+        let opt = Some(2);
+        opt
+    }; match res {
+        Some(0) => 1,
+        Some(n) => num * 2,
+        None => 0,
+    };
+
+    match unsafe {
+        let hearty_hearty_hearty = vec![240, 159, 146, 150];
+        String::from_utf8_unchecked(hearty_hearty_hearty).as_str()
+    } {
+        "💖" => 1,
+        "what" => 2,
+        _ => 3,
+    }
+}
+
 fn main() {}