diff --git a/derive_builder_core/src/block.rs b/derive_builder_core/src/block.rs
index 86b4b808..a1ce0576 100644
--- a/derive_builder_core/src/block.rs
+++ b/derive_builder_core/src/block.rs
@@ -13,7 +13,7 @@ use syn;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # #[macro_use]
 /// # extern crate quote;
 /// # extern crate derive_builder_core;
diff --git a/derive_builder_core/src/build_method.rs b/derive_builder_core/src/build_method.rs
index d9507054..26d7c4fe 100644
--- a/derive_builder_core/src/build_method.rs
+++ b/derive_builder_core/src/build_method.rs
@@ -1,4 +1,4 @@
-use doc_comment::doc_comment_from;
+use doc_comment_from;
 use proc_macro2::{Span, TokenStream};
 use quote::{ToTokens, TokenStreamExt};
 use syn;
@@ -14,7 +14,7 @@ use DEFAULT_STRUCT_NAME;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # extern crate proc_macro2;
 /// # #[macro_use]
 /// # extern crate quote;
diff --git a/derive_builder_core/src/builder.rs b/derive_builder_core/src/builder.rs
index 40ccb056..ef1b3aea 100644
--- a/derive_builder_core/src/builder.rs
+++ b/derive_builder_core/src/builder.rs
@@ -3,7 +3,7 @@ use quote::{format_ident, ToTokens, TokenStreamExt};
 use syn::punctuated::Punctuated;
 use syn::{self, Path, TraitBound, TraitBoundModifier, TypeParamBound};
 
-use doc_comment::doc_comment_from;
+use doc_comment_from;
 use BuildMethod;
 use BuilderField;
 use BuilderPattern;
@@ -16,7 +16,7 @@ use Setter;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # extern crate proc_macro2;
 /// # #[macro_use]
 /// # extern crate quote;
@@ -481,7 +481,7 @@ mod tests {
                             unimplemented!()
                         }
                     }
-                    
+
                     impl<'a, T: Debug + ::derive_builder::export::core::clone::Clone> ::derive_builder::export::core::default::Default for FooBuilder<'a, T> where T: PartialEq {
                         fn default() -> Self {
                             Self {
@@ -573,7 +573,7 @@ mod tests {
                             unimplemented!()
                         }
                     }
-                    
+
                     impl<'a, T: 'a + Default + ::derive_builder::export::core::clone::Clone> ::derive_builder::export::core::default::Default for FooBuilder<'a, T> where T: PartialEq {
                         fn default() -> Self {
                             Self {
@@ -662,7 +662,7 @@ mod tests {
                             unimplemented!()
                         }
                     }
-                    
+
                     impl<'a, T: Debug> ::derive_builder::export::core::default::Default for FooBuilder<'a, T>
                     where T: PartialEq {
                         fn default() -> Self {
diff --git a/derive_builder_core/src/builder_field.rs b/derive_builder_core/src/builder_field.rs
index c5489719..ee4a0c03 100644
--- a/derive_builder_core/src/builder_field.rs
+++ b/derive_builder_core/src/builder_field.rs
@@ -8,7 +8,7 @@ use syn;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # extern crate proc_macro2;
 /// # #[macro_use]
 /// # extern crate quote;
diff --git a/derive_builder_core/src/deprecation_notes.rs b/derive_builder_core/src/deprecation_notes.rs
index 1d53c464..92a20a40 100644
--- a/derive_builder_core/src/deprecation_notes.rs
+++ b/derive_builder_core/src/deprecation_notes.rs
@@ -12,7 +12,7 @@ use syn;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # #[macro_use]
 /// # extern crate quote;
 /// # extern crate derive_builder_core;
@@ -55,17 +55,11 @@ impl ToTokens for DeprecationNotes {
 
 impl DeprecationNotes {
     /// Appends a note to the collection.
+    #[cfg(test)]
     pub fn push(&mut self, note: String) {
         self.0.push(note)
     }
 
-    /// Extend this collection with all values from another collection.
-    pub fn extend(&mut self, other: &Self) {
-        for x in &other.0 {
-            self.0.push(x.to_owned())
-        }
-    }
-
     /// Create a view of these deprecation notes that can annotate a struct.
     pub const fn as_item(&self) -> DeprecationNotesAsItem {
         DeprecationNotesAsItem(self)
diff --git a/derive_builder_core/src/doc_comment.rs b/derive_builder_core/src/doc_comment.rs
index cc7d20b7..b23ad8ce 100644
--- a/derive_builder_core/src/doc_comment.rs
+++ b/derive_builder_core/src/doc_comment.rs
@@ -6,7 +6,7 @@ use syn::Attribute;
 ///
 /// Will expand to something like the following (depending on inner value):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # #[macro_use]
 /// # extern crate quote;
 /// # extern crate syn;
diff --git a/derive_builder_core/src/initializer.rs b/derive_builder_core/src/initializer.rs
index 08e341bd..8cfe52fd 100644
--- a/derive_builder_core/src/initializer.rs
+++ b/derive_builder_core/src/initializer.rs
@@ -13,7 +13,7 @@ use DEFAULT_STRUCT_NAME;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # extern crate proc_macro2;
 /// # #[macro_use]
 /// # extern crate quote;
diff --git a/derive_builder_core/src/lib.rs b/derive_builder_core/src/lib.rs
index 09daeb6f..2970593b 100644
--- a/derive_builder_core/src/lib.rs
+++ b/derive_builder_core/src/lib.rs
@@ -4,20 +4,13 @@
 //!
 //! * You are probably looking for the [`derive_builder`] crate,
 //!   which wraps this crate and is much more ergonomic to use.
-//! * The API of this crate might **change frequently** in the near future.
-//!   The [`derive_builder`] crate also provides a much more stable API.
 //!
 //! ## Purpose
 //!
-//! This is an internal helper library of [`derive_builder`]. Its purpose is to
-//! allow [`derive_builder`] to use its own code generation technique, if
-//! needed.
+//! This is an internal helper library of [`derive_builder`], which allows for
+//! all the logic of builder creation to be decoupled from the proc-macro entry
+//! point.
 //!
-//! [`derive_builder_core`] might also be used in crates that
-//! [`derive_builder`] depends on - again to break a dependency cycle.
-//!
-//! If [`derive_builder`] does not itself depend on _your_ crate, then you
-//! should consider using [`derive_builder`] instead of [`derive_builder_core`].
 //!
 //! [`derive_builder`]: https://!crates.io/crates/derive_builder
 //! [`derive_builder_core`]: https://!crates.io/crates/derive_builder_core
@@ -49,16 +42,16 @@ mod macro_options;
 mod options;
 mod setter;
 
-pub use block::Block;
-pub use build_method::BuildMethod;
-pub use builder::Builder;
-pub use builder_field::BuilderField;
+pub(crate) use block::Block;
+pub(crate) use build_method::BuildMethod;
+pub(crate) use builder::Builder;
+pub(crate) use builder_field::BuilderField;
 use darling::FromDeriveInput;
-pub use deprecation_notes::DeprecationNotes;
-pub use doc_comment::doc_comment_from;
-pub use initializer::Initializer;
-pub use options::BuilderPattern;
-pub use setter::Setter;
+pub(crate) use deprecation_notes::DeprecationNotes;
+pub(crate) use doc_comment::doc_comment_from;
+pub(crate) use initializer::Initializer;
+pub(crate) use options::BuilderPattern;
+pub(crate) use setter::Setter;
 
 const DEFAULT_STRUCT_NAME: &str = "__default";
 
diff --git a/derive_builder_core/src/setter.rs b/derive_builder_core/src/setter.rs
index 31995fb3..3f8fcb04 100644
--- a/derive_builder_core/src/setter.rs
+++ b/derive_builder_core/src/setter.rs
@@ -13,7 +13,7 @@ use DeprecationNotes;
 ///
 /// Will expand to something like the following (depending on settings):
 ///
-/// ```rust
+/// ```rust,ignore
 /// # extern crate proc_macro2;
 /// # #[macro_use]
 /// # extern crate quote;