stop linting [blocks_in_conditions] on match with weird attr macro case

Author: J-ZhengLi

clippy_lints/src/blocks_in_conditions.rs

@@ -5,11 +5,11 @@ 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_hir::{Block, 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;
+use rustc_span::{sym, Span};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -88,8 +88,7 @@ impl<'tcx> LateLintPass<'tcx> for BlocksInConditions {
                         );
                     }
                 } 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() {
+                    if block_is_from_expansion(block, expr.span) {
                         return;
                     }
                     // move block higher
@@ -135,3 +134,21 @@ impl<'tcx> LateLintPass<'tcx> for BlocksInConditions {
         }
     }
 }
+
+fn block_is_from_expansion(block: &Block<'_>, block_span: Span) -> bool {
+    let block_expr_span = block.expr.map(|e| e.span);
+    let block_first_stmt_span = block.stmts.first().map(|st| st.span);
+    block_span.from_expansion()
+        || matches!(block_expr_span, Some(sp) if sp.from_expansion())
+        || matches!(block_first_stmt_span, Some(sp) if sp.from_expansion())
+        || {
+            // HACK: When expr and stmt overlaps, assume it was modified by some macro.
+            if let Some(expr_span) = block_expr_span
+                && let Some(stmt_span) = block_first_stmt_span
+            {
+                expr_span.overlaps(stmt_span)
+            } else {
+                false
+            }
+        }
+}

tests/ui/blocks_in_conditions.fixed

@@ -90,7 +90,7 @@ fn block_in_match_expr(num: i32) -> i32 {
 mod issue_12016 {
     #[proc_macro_attr::fake_desugar_await]
     pub async fn await_becomes_block() -> i32 {
-        let res = await; match res {
+        match Some(1).await {
             Some(1) => 2,
             Some(2) => 3,
             _ => 0,

tests/ui/blocks_in_conditions.stderr

@@ -53,11 +53,5 @@ LL +         opt
 LL ~     }; match 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`
-  --> $DIR/blocks_in_conditions.rs:93:9
-   |
-LL |         match Some(1).await {
-   |         ^^^^^^^^^^^^^^^^^^^ help: try: `let res = await; match res`
-
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors