Extend inline_attribute_width to more AST types

src/expr.rs

@@ -416,7 +416,23 @@ pub(crate) fn format_expr(
                 attrs.last().map_or(expr.span.lo(), |attr| attr.span.hi()),
                 expr.span.lo(),
             );
-            combine_strs_with_missing_comments(context, &attrs_str, &expr_str, span, shape, false)
+
+            let allow_extend = if attrs.len() == 1 {
+                let line_len = attrs_str.len() + 1 + expr_str.len();
+                !attrs.first().unwrap().is_doc_comment()
+                    && context.config.inline_attribute_width() >= line_len
+            } else {
+                false
+            };
+
+            combine_strs_with_missing_comments(
+                context,
+                &attrs_str,
+                &expr_str,
+                span,
+                shape,
+                allow_extend,
+            )
         })
 }
 

src/items.rs

@@ -1877,7 +1877,17 @@ pub(crate) fn rewrite_struct_field(
     let prefix = rewrite_struct_field_prefix(context, field)?;
 
     let attrs_str = field.attrs.rewrite(context, shape)?;
-    let attrs_extendable = field.ident.is_none() && is_attributes_extendable(&attrs_str);
+
+    let allow_extend = if field.attrs.len() == 1 {
+        let line_len = attrs_str.len() + 1 + prefix.len();
+        !field.attrs.first().unwrap().is_doc_comment()
+            && context.config.inline_attribute_width() >= line_len
+    } else {
+        false
+    };
+
+    let attrs_extendable =
+        (field.ident.is_none() && is_attributes_extendable(&attrs_str)) || allow_extend;
     let missing_span = if field.attrs.is_empty() {
         mk_sp(field.span.lo(), field.span.lo())
     } else {
@@ -3383,13 +3393,22 @@ impl Rewrite for ast::ForeignItem {
         } else {
             mk_sp(self.attrs[self.attrs.len() - 1].span.hi(), self.span.lo())
         };
+
+        let allow_extend = if self.attrs.len() == 1 {
+            let line_len = attrs_str.len() + 1 + item_str.len();
+            !self.attrs.first().unwrap().is_doc_comment()
+                && context.config.inline_attribute_width() >= line_len
+        } else {
+            false
+        };
+
         combine_strs_with_missing_comments(
             context,
             &attrs_str,
             &item_str,
             missing_span,
             shape,
-            false,
+            allow_extend,
         )
     }
 }

tests/source/issue-3343.rs

@@ -15,6 +15,31 @@ extern crate len_is_50_;
 #[cfg(feature = "alloc")]
 extern crate len_is_51__;
 
+// https://github.com/rust-lang/rustfmt/issues/3343#issuecomment-589945611
+extern "C" {
+    #[no_mangle]
+    fn foo();
+}
+
+fn main() {
+    #[cfg(feature = "alloc")]
+    foo();
+    #[cfg(feature = "alloc")]
+    {
+        foo();
+    }
+    {
+        #[cfg(feature = "alloc")]
+        foo();
+    }
+}
+
+// https://github.com/rust-lang/rustfmt/pull/5538#issuecomment-1272367684
+struct EventConfigWidget {
+    #[widget]
+    menu_delay: Spinner<u32>,
+}
+
 /// this is a comment to test is_sugared_doc property
 use core::convert;
 

tests/target/issue-3343.rs

@@ -12,6 +12,26 @@ use total_len_is::_51___;
 #[cfg(feature = "alloc")]
 extern crate len_is_51__;
 
+// https://github.com/rust-lang/rustfmt/issues/3343#issuecomment-589945611
+extern "C" {
+    #[no_mangle] fn foo();
+}
+
+fn main() {
+    #[cfg(feature = "alloc")] foo();
+    #[cfg(feature = "alloc")] {
+        foo();
+    }
+    {
+        #[cfg(feature = "alloc")] foo();
+    }
+}
+
+// https://github.com/rust-lang/rustfmt/pull/5538#issuecomment-1272367684
+struct EventConfigWidget {
+    #[widget] menu_delay: Spinner<u32>,
+}
+
 /// this is a comment to test is_sugared_doc property
 use core::convert;