Do not add or remove block from closure body inside macro

Author: topecongiro

src/expr.rs

@@ -2299,6 +2299,10 @@ fn rewrite_last_closure(
         if prefix.contains('\n') {
             return None;
         }
+        // If we are inside macro, we do not want to add or remove block from closure body.
+        if context.inside_macro {
+            return expr.rewrite(context, shape);
+        }
 
         let body_shape = try_opt!(shape.offset_left(extra_offset));
 
@@ -2365,15 +2369,7 @@ where
             ast::ExprKind::Closure(..) => {
                 // If the argument consists of multiple closures, we do not overflow
                 // the last closure.
-                if args.len() > 1 &&
-                    args.iter()
-                        .rev()
-                        .skip(1)
-                        .filter_map(|arg| arg.to_expr())
-                        .any(|expr| match expr.node {
-                            ast::ExprKind::Closure(..) => true,
-                            _ => false,
-                        }) {
+                if args_has_many_closure(args) {
                     None
                 } else {
                     rewrite_last_closure(context, expr, shape)
@@ -2394,6 +2390,22 @@ where
     }
 }
 
+fn args_has_many_closure<T>(args: &[&T]) -> bool
+where
+    T: ToExpr,
+{
+    args.iter()
+        .filter(|arg| {
+            arg.to_expr()
+                .map(|e| match e.node {
+                    ast::ExprKind::Closure(..) => true,
+                    _ => false,
+                })
+                .unwrap_or(false)
+        })
+        .count() > 1
+}
+
 fn can_be_overflowed<'a, T>(context: &RewriteContext, args: &[&T]) -> bool
 where
     T: Rewrite + Spanned + ToExpr + 'a,

tests/source/closure-block-inside-macro.rs

@@ -0,0 +1,11 @@
+// rustfmt-fn_call_style: Block
+
+// #1547
+fuzz_target!(|data: &[u8]| if let Some(first) = data.first() {
+    let index = *first as usize;
+    if index >= ENCODINGS.len() {
+        return;
+    }
+    let encoding = ENCODINGS[index];
+    dispatch_test(encoding, &data[1..]);
+});

tests/target/closure-block-inside-macro.rs

@@ -1,12 +1,10 @@
 // rustfmt-fn_call_style: Block
 
 // #1547
-fuzz_target!(|data: &[u8]| {
-    if let Some(first) = data.first() {
-        let index = *first as usize;
-        if index >= ENCODINGS.len() {
-            return;
-        }
+fuzz_target!(|data: &[u8]| if let Some(first) = data.first() {
+    let index = *first as usize;
+    if index >= ENCODINGS.len() {
+        return;
     }
     let encoding = ENCODINGS[index];
     dispatch_test(encoding, &data[1..]);