builder_field_attr, builder_setter_attr: switch to ( ) syntx

As per
  #237 (comment)

derive_builder/src/lib.rs

@@ -565,9 +565,7 @@
 //! #[derive(Builder)]
 //! #[builder(derive(serde::Serialize))]
 //! struct Lorem {
-//!     #[builder_field_attrs(
-//!         #[serde(rename="dolor")]
-//!     )]
+//!     #[builder_field_attrs(serde(rename="dolor"))]
 //!     ipsum: String,
 //! }
 //!

derive_builder/tests/compile-fail/builder_field_attrs.rs

@@ -6,9 +6,7 @@ pub struct Lorem {
     ok: String,
 
     // This foolish repr() attribute generates an unused attribute warning
-    #[builder_field_attrs(
-        #[no_such_attribute]
-    )]
+    #[builder_field_attrs(no_such_attribute)]
     broken: String,
 }
 

derive_builder/tests/compile-fail/builder_field_attrs.stderr

@@ -1,5 +1,5 @@
 error: cannot find attribute `no_such_attribute` in this scope
-  --> tests/compile-fail/builder_field_attrs.rs:10:11
-   |
-10 |         #[no_such_attribute]
-   |           ^^^^^^^^^^^^^^^^^
+ --> tests/compile-fail/builder_field_attrs.rs:9:27
+  |
+9 |     #[builder_field_attrs(no_such_attribute)]
+  |                           ^^^^^^^^^^^^^^^^^

derive_builder/tests/compile-fail/builder_setter_attrs.rs

@@ -8,9 +8,7 @@ pub struct Lorem {
     ok: String,
 
     // This foolish repr() attribute generates an unused attribute warning
-    #[builder_setter_attrs(
-        #[must_use]
-    )]
+    #[builder_setter_attrs(must_use)]
     broken: usize,
 }
 

derive_builder/tests/compile-fail/builder_setter_attrs.stderr

@@ -1,7 +1,7 @@
 error: unused return value of `LoremBuilder::broken` that must be used
-  --> tests/compile-fail/builder_setter_attrs.rs:18:5
+  --> tests/compile-fail/builder_setter_attrs.rs:16:5
    |
-18 |     LoremBuilder::default().broken(42);
+16 |     LoremBuilder::default().broken(42);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: lint level defined here

derive_builder_core/src/macro_options/darling_opts.rs

@@ -4,8 +4,8 @@ use crate::BuildMethod;
 
 use darling::util::{Flag, PathList};
 use darling::{self, FromMeta};
-use proc_macro2::Span;
-use syn::parse::ParseStream;
+use proc_macro2::{Span, TokenStream};
+use syn::parse::{ParseStream, Parser};
 use syn::Meta;
 use syn::{self, spanned::Spanned, Attribute, Generics, Ident, Path, Visibility};
 
@@ -303,9 +303,18 @@ fn unnest_from_one_attribute(attr: syn::Attribute) -> darling::Result<Vec<Attrib
     struct ContainedAttributes(Vec<syn::Attribute>);
     impl syn::parse::Parse for ContainedAttributes {
         fn parse(input: ParseStream) -> syn::Result<Self> {
+            // Strip parentheses, and save the span of the parenthesis token
             let content;
-            let _paren_token = parenthesized!(content in input);
-            let attrs = content.call(syn::Attribute::parse_outer)?;
+            let paren_token = parenthesized!(content in input);
+            let wrap_span = paren_token.span;
+
+            // Wrap up in #[ ] instead.
+            let pound = Token![#](wrap_span); // We can't write a literal # inside quote
+            let content: TokenStream = content.parse()?;
+            let content = quote_spanned!(wrap_span=> #pound [ #content ]);
+
+            let parser = syn::Attribute::parse_outer;
+            let attrs = parser.parse2(content)?;
             Ok(Self(attrs))
         }
     }