Merging upstream version 1.72.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 893 insertions, 560 deletions

diff --git a/vendor/displaydoc/src/attr.rs b/vendor/displaydoc/src/attr.rs
index e14593556..a965d04de 100644
--- a/vendor/displaydoc/src/attr.rs
+++ b/vendor/displaydoc/src/attr.rs
@@ -1,134 +1,137 @@
-use proc_macro2::TokenStream;
-use quote::{quote, ToTokens};
-use syn::{Attribute, LitStr, Meta, Result};
-
-#[derive(Clone)]
-pub(crate) struct Display {
-    pub(crate) fmt: LitStr,
-    pub(crate) args: TokenStream,
-}
-
-pub(crate) struct VariantDisplay {
-    pub(crate) r#enum: Option<Display>,
-    pub(crate) variant: Display,
-}
-
-impl ToTokens for Display {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        let fmt = &self.fmt;
-        let args = &self.args;
-        tokens.extend(quote! {
-            write!(formatter, #fmt #args)
-        });
-    }
-}
-
-impl ToTokens for VariantDisplay {
-    fn to_tokens(&self, tokens: &mut TokenStream) {
-        if let Some(ref r#enum) = self.r#enum {
-            r#enum.to_tokens(tokens);
-            tokens.extend(quote! { ?; write!(formatter, ": ")?; });
-        }
-        self.variant.to_tokens(tokens);
-    }
-}
-
-pub(crate) struct AttrsHelper {
-    ignore_extra_doc_attributes: bool,
-    prefix_enum_doc_attributes: bool,
-}
-
-impl AttrsHelper {
-    pub(crate) fn new(attrs: &[Attribute]) -> Self {
-        let ignore_extra_doc_attributes = attrs
-            .iter()
-            .any(|attr| attr.path.is_ident("ignore_extra_doc_attributes"));
-        let prefix_enum_doc_attributes = attrs
-            .iter()
-            .any(|attr| attr.path.is_ident("prefix_enum_doc_attributes"));
-
-        Self {
-            ignore_extra_doc_attributes,
-            prefix_enum_doc_attributes,
-        }
-    }
-
-    pub(crate) fn display(&self, attrs: &[Attribute]) -> Result<Option<Display>> {
-        let displaydoc_attr = attrs.iter().find(|attr| attr.path.is_ident("displaydoc"));
-
-        if let Some(displaydoc_attr) = displaydoc_attr {
-            let lit = displaydoc_attr
-                .parse_args()
-                .expect("#[displaydoc(\"foo\")] must contain string arguments");
-            let mut display = Display {
-                fmt: lit,
-                args: TokenStream::new(),
-            };
-
-            display.expand_shorthand();
-            return Ok(Some(display));
-        }
-
-        let num_doc_attrs = attrs
-            .iter()
-            .filter(|attr| attr.path.is_ident("doc"))
-            .count();
-
-        if !self.ignore_extra_doc_attributes && num_doc_attrs > 1 {
-            panic!("Multi-line comments are disabled by default by displaydoc. Please consider using block doc comments (/** */) or adding the #[ignore_extra_doc_attributes] attribute to your type next to the derive.");
-        }
-
-        for attr in attrs {
-            if attr.path.is_ident("doc") {
-                let meta = attr.parse_meta()?;
-                let lit = match meta {
-                    Meta::NameValue(syn::MetaNameValue {
-                        lit: syn::Lit::Str(lit),
-                        ..
-                    }) => lit,
-                    _ => unimplemented!(),
-                };
-
-                // Make an attempt and cleaning up multiline doc comments
-                let doc_str = lit
-                    .value()
-                    .lines()
-                    .map(|line| line.trim().trim_start_matches('*').trim())
-                    .collect::<Vec<&str>>()
-                    .join("\n");
-
-                let lit = LitStr::new(doc_str.trim(), lit.span());
-
-                let mut display = Display {
-                    fmt: lit,
-                    args: TokenStream::new(),
-                };
-
-                display.expand_shorthand();
-                return Ok(Some(display));
-            }
-        }
-
-        Ok(None)
-    }
-
-    pub(crate) fn display_with_input(
-        &self,
-        r#enum: &[Attribute],
-        variant: &[Attribute],
-    ) -> Result<Option<VariantDisplay>> {
-        let r#enum = if self.prefix_enum_doc_attributes {
-            let result = self
-                .display(r#enum)?
-                .expect("Missing doc comment on enum with #[prefix_enum_doc_attributes]. Please remove the attribute or add a doc comment to the enum itself.");
-
-            Some(result)
-        } else {
-            None
-        };
-
-        Ok(self
-            .display(variant)?
-            .map(|variant| VariantDisplay { r#enum, variant }))
-    }
-}
+use proc_macro2::TokenStream;

+use quote::{quote, ToTokens};

+use syn::{Attribute, LitStr, Meta, Result};

+

+#[derive(Clone)]

+pub(crate) struct Display {

+    pub(crate) fmt: LitStr,

+    pub(crate) args: TokenStream,

+}

+

+pub(crate) struct VariantDisplay {

+    pub(crate) r#enum: Option<Display>,

+    pub(crate) variant: Display,

+}

+

+impl ToTokens for Display {

+    fn to_tokens(&self, tokens: &mut TokenStream) {

+        let fmt = &self.fmt;

+        let args = &self.args;

+        tokens.extend(quote! {

+            write!(formatter, #fmt #args)

+        });

+    }

+}

+

+impl ToTokens for VariantDisplay {

+    fn to_tokens(&self, tokens: &mut TokenStream) {

+        if let Some(ref r#enum) = self.r#enum {

+            r#enum.to_tokens(tokens);

+            tokens.extend(quote! { ?; write!(formatter, ": ")?; });

+        }

+        self.variant.to_tokens(tokens);

+    }

+}

+

+pub(crate) struct AttrsHelper {

+    ignore_extra_doc_attributes: bool,

+    prefix_enum_doc_attributes: bool,

+}

+

+impl AttrsHelper {

+    pub(crate) fn new(attrs: &[Attribute]) -> Self {

+        let ignore_extra_doc_attributes = attrs

+            .iter()

+            .any(|attr| attr.path().is_ident("ignore_extra_doc_attributes"));

+        let prefix_enum_doc_attributes = attrs

+            .iter()

+            .any(|attr| attr.path().is_ident("prefix_enum_doc_attributes"));

+

+        Self {

+            ignore_extra_doc_attributes,

+            prefix_enum_doc_attributes,

+        }

+    }

+

+    pub(crate) fn display(&self, attrs: &[Attribute]) -> Result<Option<Display>> {

+        let displaydoc_attr = attrs.iter().find(|attr| attr.path().is_ident("displaydoc"));

+

+        if let Some(displaydoc_attr) = displaydoc_attr {

+            let lit = displaydoc_attr

+                .parse_args()

+                .expect("#[displaydoc(\"foo\")] must contain string arguments");

+            let mut display = Display {

+                fmt: lit,

+                args: TokenStream::new(),

+            };

+

+            display.expand_shorthand();

+            return Ok(Some(display));

+        }

+

+        let num_doc_attrs = attrs

+            .iter()

+            .filter(|attr| attr.path().is_ident("doc"))

+            .count();

+

+        if !self.ignore_extra_doc_attributes && num_doc_attrs > 1 {

+            panic!("Multi-line comments are disabled by default by displaydoc. Please consider using block doc comments (/** */) or adding the #[ignore_extra_doc_attributes] attribute to your type next to the derive.");

+        }

+

+        for attr in attrs {

+            if attr.path().is_ident("doc") {

+                let lit = match &attr.meta {

+                    Meta::NameValue(syn::MetaNameValue {

+                        value:

+                            syn::Expr::Lit(syn::ExprLit {

+                                lit: syn::Lit::Str(lit),

+                                ..

+                            }),

+                        ..

+                    }) => lit,

+                    _ => unimplemented!(),

+                };

+

+                // Make an attempt at cleaning up multiline doc comments.

+                let doc_str = lit

+                    .value()

+                    .lines()

+                    .map(|line| line.trim().trim_start_matches('*').trim())

+                    .collect::<Vec<&str>>()

+                    .join("\n");

+

+                let lit = LitStr::new(doc_str.trim(), lit.span());

+

+                let mut display = Display {

+                    fmt: lit,

+                    args: TokenStream::new(),

+                };

+

+                display.expand_shorthand();

+                return Ok(Some(display));

+            }

+        }

+

+        Ok(None)

+    }

+

+    pub(crate) fn display_with_input(

+        &self,

+        r#enum: &[Attribute],

+        variant: &[Attribute],

+    ) -> Result<Option<VariantDisplay>> {

+        let r#enum = if self.prefix_enum_doc_attributes {

+            let result = self

+                .display(r#enum)?

+                .expect("Missing doc comment on enum with #[prefix_enum_doc_attributes]. Please remove the attribute or add a doc comment to the enum itself.");

+

+            Some(result)

+        } else {

+            None

+        };

+

+        Ok(self

+            .display(variant)?

+            .map(|variant| VariantDisplay { r#enum, variant }))

+    }

+}

diff --git a/vendor/displaydoc/src/expand.rs b/vendor/displaydoc/src/expand.rs
index 6904cbc8c..8a84390be 100644
--- a/vendor/displaydoc/src/expand.rs
+++ b/vendor/displaydoc/src/expand.rs
@@ -1,145 +1,410 @@
-use super::attr::AttrsHelper;
-use proc_macro2::TokenStream;
-use quote::{format_ident, quote};
-use syn::{Data, DataEnum, DataStruct, DeriveInput, Error, Fields, Result};
-
-pub(crate) fn derive(input: &DeriveInput) -> Result<TokenStream> {
-    let impls = match &input.data {
-        Data::Struct(data) => impl_struct(input, data),
-        Data::Enum(data) => impl_enum(input, data),
-        Data::Union(_) => Err(Error::new_spanned(input, "Unions are not supported")),
-    }?;
-
-    let helpers = specialization();
-    let dummy_const = format_ident!("_DERIVE_Display_FOR_{}", input.ident);
-    Ok(quote! {
-        #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
-        const #dummy_const: () = {
-            #helpers
-            #impls
-        };
-    })
-}
-
-#[cfg(feature = "std")]
-fn specialization() -> TokenStream {
-    quote! {
-        trait DisplayToDisplayDoc {
-            fn __displaydoc_display(&self) -> Self;
-        }
-
-        impl<T: core::fmt::Display> DisplayToDisplayDoc for &T {
-            fn __displaydoc_display(&self) -> Self {
-                self
-            }
-        }
-
-        // If the `std` feature gets enabled we want to ensure that any crate
-        // using displaydoc can still reference the std crate, which is already
-        // being compiled in by whoever enabled the `std` feature in
-        // `displaydoc`, even if the crates using displaydoc are no_std.
-        extern crate std;
-
-        trait PathToDisplayDoc {
-            fn __displaydoc_display(&self) -> std::path::Display<'_>;
-        }
-
-        impl PathToDisplayDoc for std::path::Path {
-            fn __displaydoc_display(&self) -> std::path::Display<'_> {
-                self.display()
-            }
-        }
-
-        impl PathToDisplayDoc for std::path::PathBuf {
-            fn __displaydoc_display(&self) -> std::path::Display<'_> {
-                self.display()
-            }
-        }
-    }
-}
-
-#[cfg(not(feature = "std"))]
-fn specialization() -> TokenStream {
-    quote! {}
-}
-
-fn impl_struct(input: &DeriveInput, data: &DataStruct) -> Result<TokenStream> {
-    let ty = &input.ident;
-    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
-
-    let helper = AttrsHelper::new(&input.attrs);
-
-    let display = helper.display(&input.attrs)?.map(|display| {
-        let pat = match &data.fields {
-            Fields::Named(fields) => {
-                let var = fields.named.iter().map(|field| &field.ident);
-                quote!(Self { #(#var),* })
-            }
-            Fields::Unnamed(fields) => {
-                let var = (0..fields.unnamed.len()).map(|i| format_ident!("_{}", i));
-                quote!(Self(#(#var),*))
-            }
-            Fields::Unit => quote!(_),
-        };
-        quote! {
-            impl #impl_generics core::fmt::Display for #ty #ty_generics #where_clause {
-                fn fmt(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {
-                    #[allow(unused_variables)]
-                    let #pat = self;
-                    #display
-                }
-            }
-        }
-    });
-
-    Ok(quote! { #display })
-}
-
-fn impl_enum(input: &DeriveInput, data: &DataEnum) -> Result<TokenStream> {
-    let ty = &input.ident;
-    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
-
-    let helper = AttrsHelper::new(&input.attrs);
-
-    let displays = data
-        .variants
-        .iter()
-        .map(|variant| helper.display_with_input(&input.attrs, &variant.attrs))
-        .collect::<Result<Vec<_>>>()?;
-
-    if displays.iter().any(Option::is_some) {
-        let arms = data
-            .variants
-            .iter()
-            .zip(displays)
-            .map(|(variant, display)| {
-                let display =
-                    display.ok_or_else(|| Error::new_spanned(variant, "missing doc comment"))?;
-                let ident = &variant.ident;
-                Ok(match &variant.fields {
-                    Fields::Named(fields) => {
-                        let var = fields.named.iter().map(|field| &field.ident);
-                        quote!(#ty::#ident { #(#var),* } => { #display })
-                    }
-                    Fields::Unnamed(fields) => {
-                        let var = (0..fields.unnamed.len()).map(|i| format_ident!("_{}", i));
-                        quote!(#ty::#ident(#(#var),*) => { #display })
-                    }
-                    Fields::Unit => quote!(#ty::#ident => { #display }),
-                })
-            })
-            .collect::<Result<Vec<_>>>()?;
-        Ok(quote! {
-            impl #impl_generics core::fmt::Display for #ty #ty_generics #where_clause {
-                fn fmt(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {
-                    #[allow(unused_variables)]
-                    match self {
-                        #(#arms,)*
-                    }
-                }
-            }
-        })
-    } else {
-        Err(Error::new_spanned(input, "Missing doc comments"))
-    }
-}
+use super::attr::AttrsHelper;

+use proc_macro2::{Span, TokenStream};

+use quote::{format_ident, quote};

+use syn::{

+    punctuated::Punctuated,

+    token::{Colon, Comma, PathSep, Plus, Where},

+    Data, DataEnum, DataStruct, DeriveInput, Error, Fields, Generics, Ident, Path, PathArguments,

+    PathSegment, PredicateType, Result, TraitBound, TraitBoundModifier, Type, TypeParam,

+    TypeParamBound, TypePath, WhereClause, WherePredicate,

+};

+

+use std::collections::HashMap;

+

+pub(crate) fn derive(input: &DeriveInput) -> Result<TokenStream> {

+    let impls = match &input.data {

+        Data::Struct(data) => impl_struct(input, data),

+        Data::Enum(data) => impl_enum(input, data),

+        Data::Union(_) => Err(Error::new_spanned(input, "Unions are not supported")),

+    }?;

+

+    let helpers = specialization();

+    let dummy_const = format_ident!("_DERIVE_Display_FOR_{}", input.ident);

+    Ok(quote! {

+        #[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]

+        const #dummy_const: () = {

+            #helpers

+            #impls

+        };

+    })

+}

+

+#[cfg(feature = "std")]

+fn specialization() -> TokenStream {

+    quote! {

+        trait DisplayToDisplayDoc {

+            fn __displaydoc_display(&self) -> Self;

+        }

+

+        impl<T: core::fmt::Display> DisplayToDisplayDoc for &T {

+            fn __displaydoc_display(&self) -> Self {

+                self

+            }

+        }

+

+        // If the `std` feature gets enabled we want to ensure that any crate

+        // using displaydoc can still reference the std crate, which is already

+        // being compiled in by whoever enabled the `std` feature in

+        // `displaydoc`, even if the crates using displaydoc are no_std.

+        extern crate std;

+

+        trait PathToDisplayDoc {

+            fn __displaydoc_display(&self) -> std::path::Display<'_>;

+        }

+

+        impl PathToDisplayDoc for std::path::Path {

+            fn __displaydoc_display(&self) -> std::path::Display<'_> {

+                self.display()

+            }

+        }

+

+        impl PathToDisplayDoc for std::path::PathBuf {

+            fn __displaydoc_display(&self) -> std::path::Display<'_> {

+                self.display()

+            }

+        }

+    }

+}

+

+#[cfg(not(feature = "std"))]

+fn specialization() -> TokenStream {

+    quote! {}

+}

+

+fn impl_struct(input: &DeriveInput, data: &DataStruct) -> Result<TokenStream> {

+    let ty = &input.ident;

+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();

+    let where_clause = generate_where_clause(&input.generics, where_clause);

+

+    let helper = AttrsHelper::new(&input.attrs);

+

+    let display = helper.display(&input.attrs)?.map(|display| {

+        let pat = match &data.fields {

+            Fields::Named(fields) => {

+                let var = fields.named.iter().map(|field| &field.ident);

+                quote!(Self { #(#var),* })

+            }

+            Fields::Unnamed(fields) => {

+                let var = (0..fields.unnamed.len()).map(|i| format_ident!("_{}", i));

+                quote!(Self(#(#var),*))

+            }

+            Fields::Unit => quote!(_),

+        };

+        quote! {

+            impl #impl_generics core::fmt::Display for #ty #ty_generics #where_clause {

+                fn fmt(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {

+                    // NB: This destructures the fields of `self` into named variables (for unnamed

+                    // fields, it uses _0, _1, etc as above). The `#[allow(unused_variables)]`

+                    // section means it doesn't have to parse the individual field references out of

+                    // the docstring.

+                    #[allow(unused_variables)]

+                    let #pat = self;

+                    #display

+                }

+            }

+        }

+    });

+

+    Ok(quote! { #display })

+}

+

+/// Create a `where` predicate for `ident`, without any [bound][TypeParamBound]s yet.

+fn new_empty_where_type_predicate(ident: Ident) -> PredicateType {

+    let mut path_segments = Punctuated::<PathSegment, PathSep>::new();

+    path_segments.push_value(PathSegment {

+        ident,

+        arguments: PathArguments::None,

+    });

+    PredicateType {

+        lifetimes: None,

+        bounded_ty: Type::Path(TypePath {

+            qself: None,

+            path: Path {

+                leading_colon: None,

+                segments: path_segments,

+            },

+        }),

+        colon_token: Colon {

+            spans: [Span::call_site()],

+        },

+        bounds: Punctuated::<TypeParamBound, Plus>::new(),

+    }

+}

+

+/// Create a `where` clause that we can add [WherePredicate]s to.

+fn new_empty_where_clause() -> WhereClause {

+    WhereClause {

+        where_token: Where {

+            span: Span::call_site(),

+        },

+        predicates: Punctuated::<WherePredicate, Comma>::new(),

+    }

+}

+

+enum UseGlobalPrefix {

+    LeadingColon,

+    #[allow(dead_code)]

+    NoLeadingColon,

+}

+

+/// Create a path with segments composed of [Idents] *without* any [PathArguments].

+fn join_paths(name_segments: &[&str], use_global_prefix: UseGlobalPrefix) -> Path {

+    let mut segments = Punctuated::<PathSegment, PathSep>::new();

+    assert!(!name_segments.is_empty());

+    segments.push_value(PathSegment {

+        ident: Ident::new(name_segments[0], Span::call_site()),

+        arguments: PathArguments::None,

+    });

+    for name in name_segments[1..].iter() {

+        segments.push_punct(PathSep {

+            spans: [Span::call_site(), Span::mixed_site()],

+        });

+        segments.push_value(PathSegment {

+            ident: Ident::new(name, Span::call_site()),

+            arguments: PathArguments::None,

+        });

+    }

+    Path {

+        leading_colon: match use_global_prefix {

+            UseGlobalPrefix::LeadingColon => Some(PathSep {

+                spans: [Span::call_site(), Span::mixed_site()],

+            }),

+            UseGlobalPrefix::NoLeadingColon => None,

+        },

+        segments,

+    }

+}

+

+/// Push `new_type_predicate` onto the end of `where_clause`.

+fn append_where_clause_type_predicate(

+    where_clause: &mut WhereClause,

+    new_type_predicate: PredicateType,

+) {

+    // Push a comma at the end if there are already any `where` predicates.

+    if !where_clause.predicates.is_empty() {

+        where_clause.predicates.push_punct(Comma {

+            spans: [Span::call_site()],

+        });

+    }

+    where_clause

+        .predicates

+        .push_value(WherePredicate::Type(new_type_predicate));

+}

+

+/// Add a requirement for [core::fmt::Display] to a `where` predicate for some type.

+fn add_display_constraint_to_type_predicate(

+    predicate_that_needs_a_display_impl: &mut PredicateType,

+) {

+    // Create a `Path` of `::core::fmt::Display`.

+    let display_path = join_paths(&["core", "fmt", "Display"], UseGlobalPrefix::LeadingColon);

+

+    let display_bound = TypeParamBound::Trait(TraitBound {

+        paren_token: None,

+        modifier: TraitBoundModifier::None,

+        lifetimes: None,

+        path: display_path,

+    });

+    if !predicate_that_needs_a_display_impl.bounds.is_empty() {

+        predicate_that_needs_a_display_impl.bounds.push_punct(Plus {

+            spans: [Span::call_site()],

+        });

+    }

+

+    predicate_that_needs_a_display_impl

+        .bounds

+        .push_value(display_bound);

+}

+

+/// Map each declared generic type parameter to the set of all trait boundaries declared on it.

+///

+/// These boundaries may come from the declaration site:

+///     pub enum E<T: MyTrait> { ... }

+/// or a `where` clause after the parameter declarations:

+///     pub enum E<T> where T: MyTrait { ... }

+/// This method will return the boundaries from both of those cases.

+fn extract_trait_constraints_from_source(

+    where_clause: &WhereClause,

+    type_params: &[&TypeParam],

+) -> HashMap<Ident, Vec<TraitBound>> {

+    // Add trait bounds provided at the declaration site of type parameters for the struct/enum.

+    let mut param_constraint_mapping: HashMap<Ident, Vec<TraitBound>> = type_params

+        .iter()

+        .map(|type_param| {

+            let trait_bounds: Vec<TraitBound> = type_param

+                .bounds

+                .iter()

+                .flat_map(|bound| match bound {

+                    TypeParamBound::Trait(trait_bound) => Some(trait_bound),

+                    _ => None,

+                })

+                .cloned()

+                .collect();

+            (type_param.ident.clone(), trait_bounds)

+        })

+        .collect();

+

+    // Add trait bounds from `where` clauses, which may be type parameters or types containing

+    // those parameters.

+    for predicate in where_clause.predicates.iter() {

+        // We only care about type and not lifetime constraints here.

+        if let WherePredicate::Type(ref pred_ty) = predicate {

+            let ident = match &pred_ty.bounded_ty {

+                Type::Path(TypePath { path, qself: None }) => match path.get_ident() {

+                    None => continue,

+                    Some(ident) => ident,

+                },

+                _ => continue,

+            };

+            // We ignore any type constraints that aren't direct references to type

+            // parameters of the current enum of struct definition. No types can be

+            // constrained in a `where` clause unless they are a type parameter or a generic

+            // type instantiated with one of the type parameters, so by only allowing single

+            // identifiers, we can be sure that the constrained type is a type parameter

+            // that is contained in `param_constraint_mapping`.

+            if let Some((_, ref mut known_bounds)) = param_constraint_mapping

+                .iter_mut()

+                .find(|(id, _)| *id == ident)

+            {

+                for bound in pred_ty.bounds.iter() {

+                    // We only care about trait bounds here.

+                    if let TypeParamBound::Trait(ref bound) = bound {

+                        known_bounds.push(bound.clone());

+                    }

+                }

+            }

+        }

+    }

+

+    param_constraint_mapping

+}

+

+/// Hygienically add `where _: Display` to the set of [TypeParamBound]s for `ident`, creating such

+/// a set if necessary.

+fn ensure_display_in_where_clause_for_type(where_clause: &mut WhereClause, ident: Ident) {

+    for pred_ty in where_clause

+        .predicates

+        .iter_mut()

+        // Find the `where` predicate constraining the current type param, if it exists.

+        .flat_map(|predicate| match predicate {

+            WherePredicate::Type(pred_ty) => Some(pred_ty),

+            // We're looking through type constraints, not lifetime constraints.

+            _ => None,

+        })

+    {

+        // Do a complicated destructuring in order to check if the type being constrained in this

+        // `where` clause is the type we're looking for, so we can use the mutable reference to

+        // `pred_ty` if so.

+        let matches_desired_type = matches!(

+            &pred_ty.bounded_ty,

+            Type::Path(TypePath { path, .. }) if Some(&ident) == path.get_ident());

+        if matches_desired_type {

+            add_display_constraint_to_type_predicate(pred_ty);

+            return;

+        }

+    }

+

+    // If there is no `where` predicate for the current type param, we will construct one.

+    let mut new_type_predicate = new_empty_where_type_predicate(ident);

+    add_display_constraint_to_type_predicate(&mut new_type_predicate);

+    append_where_clause_type_predicate(where_clause, new_type_predicate);

+}

+

+/// For all declared type parameters, add a [core::fmt::Display] constraint, unless the type

+/// parameter already has any type constraint.

+fn ensure_where_clause_has_display_for_all_unconstrained_members(

+    where_clause: &mut WhereClause,

+    type_params: &[&TypeParam],

+) {

+    let param_constraint_mapping = extract_trait_constraints_from_source(where_clause, type_params);

+

+    for (ident, known_bounds) in param_constraint_mapping.into_iter() {

+        // If the type parameter has any constraints already, we don't want to touch it, to avoid

+        // breaking use cases where a type parameter only needs to impl `Debug`, for example.

+        if known_bounds.is_empty() {

+            ensure_display_in_where_clause_for_type(where_clause, ident);

+        }

+    }

+}

+

+/// Generate a `where` clause that ensures all generic type parameters `impl`

+/// [core::fmt::Display] unless already constrained.

+///

+/// This approach allows struct/enum definitions deriving [crate::Display] to avoid hardcoding

+/// a [core::fmt::Display] constraint into every type parameter.

+///

+/// If the type parameter isn't already constrained, we add a `where _: Display` clause to our

+/// display implementation to expect to be able to format every enum case or struct member.

+///

+/// In fact, we would preferably only require `where _: Display` or `where _: Debug` where the

+/// format string actually requires it. However, while [`std::fmt` defines a formal syntax for

+/// `format!()`][format syntax], it *doesn't* expose the actual logic to parse the format string,

+/// which appears to live in [`rustc_parse_format`]. While we use the [`syn`] crate to parse rust

+/// syntax, it also doesn't currently provide any method to introspect a `format!()` string. It

+/// would be nice to contribute this upstream in [`syn`].

+///

+/// [format syntax]: std::fmt#syntax

+/// [`rustc_parse_format`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_parse_format/index.html

+fn generate_where_clause(generics: &Generics, where_clause: Option<&WhereClause>) -> WhereClause {

+    let mut where_clause = where_clause.cloned().unwrap_or_else(new_empty_where_clause);

+    let type_params: Vec<&TypeParam> = generics.type_params().collect();

+    ensure_where_clause_has_display_for_all_unconstrained_members(&mut where_clause, &type_params);

+    where_clause

+}

+

+fn impl_enum(input: &DeriveInput, data: &DataEnum) -> Result<TokenStream> {

+    let ty = &input.ident;

+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();

+    let where_clause = generate_where_clause(&input.generics, where_clause);

+

+    let helper = AttrsHelper::new(&input.attrs);

+

+    let displays = data

+        .variants

+        .iter()

+        .map(|variant| helper.display_with_input(&input.attrs, &variant.attrs))

+        .collect::<Result<Vec<_>>>()?;

+

+    if data.variants.is_empty() {

+        Ok(quote! {

+            impl #impl_generics core::fmt::Display for #ty #ty_generics #where_clause {

+                fn fmt(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {

+                    unreachable!("empty enums cannot be instantiated and thus cannot be printed")

+                }

+            }

+        })

+    } else if displays.iter().any(Option::is_some) {

+        let arms = data

+            .variants

+            .iter()

+            .zip(displays)

+            .map(|(variant, display)| {

+                let display =

+                    display.ok_or_else(|| Error::new_spanned(variant, "missing doc comment"))?;

+                let ident = &variant.ident;

+                Ok(match &variant.fields {

+                    Fields::Named(fields) => {

+                        let var = fields.named.iter().map(|field| &field.ident);

+                        quote!(Self::#ident { #(#var),* } => { #display })

+                    }

+                    Fields::Unnamed(fields) => {

+                        let var = (0..fields.unnamed.len()).map(|i| format_ident!("_{}", i));

+                        quote!(Self::#ident(#(#var),*) => { #display })

+                    }

+                    Fields::Unit => quote!(Self::#ident => { #display }),

+                })

+            })

+            .collect::<Result<Vec<_>>>()?;

+        Ok(quote! {

+            impl #impl_generics core::fmt::Display for #ty #ty_generics #where_clause {

+                fn fmt(&self, formatter: &mut core::fmt::Formatter) -> core::fmt::Result {

+                    #[allow(unused_variables)]

+                    match self {

+                        #(#arms,)*

+                    }

+                }

+            }

+        })

+    } else {

+        Err(Error::new_spanned(input, "Missing doc comments"))

+    }

+}

diff --git a/vendor/displaydoc/src/fmt.rs b/vendor/displaydoc/src/fmt.rs
index 5848557ea..3334a82ff 100644
--- a/vendor/displaydoc/src/fmt.rs
+++ b/vendor/displaydoc/src/fmt.rs
@@ -1,159 +1,159 @@
-use crate::attr::Display;
-use proc_macro2::TokenStream;
-use quote::quote_spanned;
-use syn::{Ident, LitStr};
-
-macro_rules! peek_next {
-    ($read:ident) => {
-        match $read.chars().next() {
-            Some(next) => next,
-            None => return,
-        }
-    };
-}
-
-impl Display {
-    // Transform `"error {var}"` to `"error {}", var`.
-    pub(crate) fn expand_shorthand(&mut self) {
-        let span = self.fmt.span();
-        let fmt = self.fmt.value();
-        let mut read = fmt.as_str();
-        let mut out = String::new();
-        let mut args = TokenStream::new();
-
-        while let Some(brace) = read.find('{') {
-            out += &read[..=brace];
-            read = &read[brace + 1..];
-
-            // skip cases where we find a {{
-            if read.starts_with('{') {
-                out.push('{');
-                read = &read[1..];
-                continue;
-            }
-
-            let next = peek_next!(read);
-
-            let var = match next {
-                '0'..='9' => take_int(&mut read),
-                'a'..='z' | 'A'..='Z' | '_' => take_ident(&mut read),
-                _ => return,
-            };
-
-            let ident = Ident::new(&var, span);
-
-            let next = peek_next!(read);
-
-            let arg = if cfg!(feature = "std") && next == '}' {
-                quote_spanned!(span=> , #ident.__displaydoc_display())
-            } else {
-                quote_spanned!(span=> , #ident)
-            };
-
-            args.extend(arg);
-        }
-
-        out += read;
-        self.fmt = LitStr::new(&out, self.fmt.span());
-        self.args = args;
-    }
-}
-
-fn take_int(read: &mut &str) -> String {
-    let mut int = String::new();
-    int.push('_');
-    for (i, ch) in read.char_indices() {
-        match ch {
-            '0'..='9' => int.push(ch),
-            _ => {
-                *read = &read[i..];
-                break;
-            }
-        }
-    }
-    int
-}
-
-fn take_ident(read: &mut &str) -> String {
-    let mut ident = String::new();
-    for (i, ch) in read.char_indices() {
-        match ch {
-            'a'..='z' | 'A'..='Z' | '0'..='9' | '_' => ident.push(ch),
-            _ => {
-                *read = &read[i..];
-                break;
-            }
-        }
-    }
-    ident
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use pretty_assertions::assert_eq;
-    use proc_macro2::Span;
-
-    fn assert(input: &str, fmt: &str, args: &str) {
-        let mut display = Display {
-            fmt: LitStr::new(input, Span::call_site()),
-            args: TokenStream::new(),
-        };
-        display.expand_shorthand();
-        assert_eq!(fmt, display.fmt.value());
-        assert_eq!(args, display.args.to_string());
-    }
-
-    #[test]
-    fn test_expand() {
-        assert("fn main() {{ }}", "fn main() {{ }}", "");
-    }
-
-    #[test]
-    #[cfg_attr(not(feature = "std"), ignore)]
-    fn test_std_expand() {
-        assert(
-            "{v} {v:?} {0} {0:?}",
-            "{} {:?} {} {:?}",
-            ", v . __displaydoc_display () , v , _0 . __displaydoc_display () , _0",
-        );
-        assert("error {var}", "error {}", ", var . __displaydoc_display ()");
-
-        assert(
-            "error {var1}",
-            "error {}",
-            ", var1 . __displaydoc_display ()",
-        );
-
-        assert(
-            "error {var1var}",
-            "error {}",
-            ", var1var . __displaydoc_display ()",
-        );
-
-        assert(
-            "The path {0}",
-            "The path {}",
-            ", _0 . __displaydoc_display ()",
-        );
-        assert("The path {0:?}", "The path {:?}", ", _0");
-    }
-
-    #[test]
-    #[cfg_attr(feature = "std", ignore)]
-    fn test_nostd_expand() {
-        assert(
-            "{v} {v:?} {0} {0:?}",
-            "{} {:?} {} {:?}",
-            ", v , v , _0 , _0",
-        );
-        assert("error {var}", "error {}", ", var");
-
-        assert("The path {0}", "The path {}", ", _0");
-        assert("The path {0:?}", "The path {:?}", ", _0");
-
-        assert("error {var1}", "error {}", ", var1");
-
-        assert("error {var1var}", "error {}", ", var1var");
-    }
-}
+use crate::attr::Display;

+use proc_macro2::TokenStream;

+use quote::quote_spanned;

+use syn::{Ident, LitStr};

+

+macro_rules! peek_next {

+    ($read:ident) => {

+        match $read.chars().next() {

+            Some(next) => next,

+            None => return,

+        }

+    };

+}

+

+impl Display {

+    // Transform `"error {var}"` to `"error {}", var`.

+    pub(crate) fn expand_shorthand(&mut self) {

+        let span = self.fmt.span();

+        let fmt = self.fmt.value();

+        let mut read = fmt.as_str();

+        let mut out = String::new();

+        let mut args = TokenStream::new();

+

+        while let Some(brace) = read.find('{') {

+            out += &read[..=brace];

+            read = &read[brace + 1..];

+

+            // skip cases where we find a {{

+            if read.starts_with('{') {

+                out.push('{');

+                read = &read[1..];

+                continue;

+            }

+

+            let next = peek_next!(read);

+

+            let var = match next {

+                '0'..='9' => take_int(&mut read),

+                'a'..='z' | 'A'..='Z' | '_' => take_ident(&mut read),

+                _ => return,

+            };

+

+            let ident = Ident::new(&var, span);

+

+            let next = peek_next!(read);

+

+            let arg = if cfg!(feature = "std") && next == '}' {

+                quote_spanned!(span=> , #ident.__displaydoc_display())

+            } else {

+                quote_spanned!(span=> , #ident)

+            };

+

+            args.extend(arg);

+        }

+

+        out += read;

+        self.fmt = LitStr::new(&out, self.fmt.span());

+        self.args = args;

+    }

+}

+

+fn take_int(read: &mut &str) -> String {

+    let mut int = String::new();

+    int.push('_');

+    for (i, ch) in read.char_indices() {

+        match ch {

+            '0'..='9' => int.push(ch),

+            _ => {

+                *read = &read[i..];

+                break;

+            }

+        }

+    }

+    int

+}

+

+fn take_ident(read: &mut &str) -> String {

+    let mut ident = String::new();

+    for (i, ch) in read.char_indices() {

+        match ch {

+            'a'..='z' | 'A'..='Z' | '0'..='9' | '_' => ident.push(ch),

+            _ => {

+                *read = &read[i..];

+                break;

+            }

+        }

+    }

+    ident

+}

+

+#[cfg(test)]

+mod tests {

+    use super::*;

+    use pretty_assertions::assert_eq;

+    use proc_macro2::Span;

+

+    fn assert(input: &str, fmt: &str, args: &str) {

+        let mut display = Display {

+            fmt: LitStr::new(input, Span::call_site()),

+            args: TokenStream::new(),

+        };

+        display.expand_shorthand();

+        assert_eq!(fmt, display.fmt.value());

+        assert_eq!(args, display.args.to_string());

+    }

+

+    #[test]

+    fn test_expand() {

+        assert("fn main() {{ }}", "fn main() {{ }}", "");

+    }

+

+    #[test]

+    #[cfg_attr(not(feature = "std"), ignore)]

+    fn test_std_expand() {

+        assert(

+            "{v} {v:?} {0} {0:?}",

+            "{} {:?} {} {:?}",

+            ", v . __displaydoc_display () , v , _0 . __displaydoc_display () , _0",

+        );

+        assert("error {var}", "error {}", ", var . __displaydoc_display ()");

+

+        assert(

+            "error {var1}",

+            "error {}",

+            ", var1 . __displaydoc_display ()",

+        );

+

+        assert(

+            "error {var1var}",

+            "error {}",

+            ", var1var . __displaydoc_display ()",

+        );

+

+        assert(

+            "The path {0}",

+            "The path {}",

+            ", _0 . __displaydoc_display ()",

+        );

+        assert("The path {0:?}", "The path {:?}", ", _0");

+    }

+

+    #[test]

+    #[cfg_attr(feature = "std", ignore)]

+    fn test_nostd_expand() {

+        assert(

+            "{v} {v:?} {0} {0:?}",

+            "{} {:?} {} {:?}",

+            ", v , v , _0 , _0",

+        );

+        assert("error {var}", "error {}", ", var");

+

+        assert("The path {0}", "The path {}", ", _0");

+        assert("The path {0:?}", "The path {:?}", ", _0");

+

+        assert("error {var1}", "error {}", ", var1");

+

+        assert("error {var1var}", "error {}", ", var1var");

+    }

+}

diff --git a/vendor/displaydoc/src/lib.rs b/vendor/displaydoc/src/lib.rs
index 083c61384..e4653d675 100644
--- a/vendor/displaydoc/src/lib.rs
+++ b/vendor/displaydoc/src/lib.rs
@@ -1,122 +1,187 @@
-//! This library provides a convenient derive macro for the standard library's
-//! [`core::fmt::Display`] trait.
-//!
-//! [`core::fmt::Display`]: https://doc.rust-lang.org/std/fmt/trait.Display.html
-//!
-//! ```toml
-//! [dependencies]
-//! displaydoc = "0.2"
-//! ```
-//!
-//! *Compiler support: requires rustc 1.31+*
-//!
-//! <br>
-//!
-//! ## Example
-//!
-//! ```rust
-//! use std::io;
-//! use displaydoc::Display;
-//! use thiserror::Error;
-//!
-//! #[derive(Display, Error, Debug)]
-//! pub enum DataStoreError {
-//!     /// data store disconnected
-//!     Disconnect(#[source] io::Error),
-//!     /// the data for key `{0}` is not available
-//!     Redaction(String),
-//!     /// invalid header (expected {expected:?}, found {found:?})
-//!     InvalidHeader {
-//!         expected: String,
-//!         found: String,
-//!     },
-//!     /// unknown data store error
-//!     Unknown,
-//! }
-//! ```
-//!
-//! <br>
-//!
-//! ## Details
-//!
-//! - A `Display` impl is generated for your type if you provide doc comment
-//!   messages on the struct or each variant of your enum, as shown above in the
-//!   example.
-//!
-//!   The messages support a shorthand for interpolating fields from the error.
-//!
-//!     - `/// {var}` ⟶ `write!("{}", self.var)`
-//!     - `/// {0}` ⟶ `write!("{}", self.0)`
-//!     - `/// {var:?}` ⟶ `write!("{:?}", self.var)`
-//!     - `/// {0:?}` ⟶ `write!("{:?}", self.0)`
-//!
-//! - Two optional attributes can be added to your types next to the derive:
-//!
-//!     - `#[ignore_extra_doc_attributes]` makes the macro ignore any doc
-//!       comment attributes (or `///` lines) after the first. Multi-line
-//!       comments using `///` are otherwise treated as an error, so use this
-//!       attribute or consider switching to block doc comments (`/** */`).
-//!
-//!     - `#[prefix_enum_doc_attributes]` combines the doc comment message on
-//!       your enum itself with the messages for each variant, in the format
-//!       “enum: variant”. When added to an enum, the doc comment on the enum
-//!       becomes mandatory. When added to any other type, it has no effect.
-//!
-//! - In case you want to have an independent doc comment, the
-//!   `#[displaydoc("...")` atrribute may be used on the variant or struct to
-//!   override it.
-//!
-//! <br>
-//!
-//! ## FAQ
-//!
-//! 1. **Is this crate `no_std` compatible?**
-//!     * Yes! This crate implements the `core::fmt::Display` trait not the `std::fmt::Display` trait so it should work in `std` and `no_std` environments. Just add `default-features = false`.
-//!
-//! 2. **Does this crate work with `Path` and `PathBuf` via the `Display` trait?**
-//!     * Yuuup. This crate uses @dtolnay's [autoref specialization technique](https://github.com/dtolnay/case-studies/blob/master/autoref-specialization/README.md) to add a special trait for types to get the display impl, it then specializes for `Path` and `PathBuf` and when either of these types are found it calls `self.display()` to get a `std::path::Display<'_>` type which can be used with the Display format specifier!
-#![doc(html_root_url = "https://docs.rs/displaydoc/0.2.3")]
-#![cfg_attr(docsrs, feature(doc_cfg))]
-#![warn(
-    rust_2018_idioms,
-    unreachable_pub,
-    bad_style,
-    const_err,
-    dead_code,
-    improper_ctypes,
-    non_shorthand_field_patterns,
-    no_mangle_generic_items,
-    overflowing_literals,
-    path_statements,
-    patterns_in_fns_without_body,
-    private_in_public,
-    unconditional_recursion,
-    unused,
-    unused_allocation,
-    unused_comparisons,
-    unused_parens,
-    while_true
-)]
-#![allow(clippy::try_err)]
-
-#[allow(unused_extern_crates)]
-extern crate proc_macro;
-
-mod attr;
-mod expand;
-mod fmt;
-
-use proc_macro::TokenStream;
-use syn::{parse_macro_input, DeriveInput};
-
-/// Derive macro for implementing `Display` via doc comment attributes
-#[proc_macro_derive(
-    Display,
-    attributes(ignore_extra_doc_attributes, prefix_enum_doc_attributes, displaydoc)
-)]
-pub fn derive_error(input: TokenStream) -> TokenStream {
-    let input = parse_macro_input!(input as DeriveInput);
-    expand::derive(&input)
-        .unwrap_or_else(|err| err.to_compile_error())
-        .into()
-}
+//! This library provides a convenient derive macro for the standard library's

+//! [`core::fmt::Display`] trait.

+//!

+//! [`core::fmt::Display`]: https://doc.rust-lang.org/std/fmt/trait.Display.html

+//!

+//! ```toml

+//! [dependencies]

+//! displaydoc = "0.2"

+//! ```

+//!

+//! *Compiler support: requires rustc 1.56+*

+//!

+//! <br>

+//!

+//! ## Example

+//!

+//! *Demonstration alongside the [`Error`][std::error::Error] derive macro from [`thiserror`](https://docs.rs/thiserror/1.0.25/thiserror/index.html),

+//! to propagate source locations from [`io::Error`][std::io::Error] with the `#[source]` attribute:*

+//! ```rust

+//! use std::io;

+//! use displaydoc::Display;

+//! use thiserror::Error;

+//!

+//! #[derive(Display, Error, Debug)]

+//! pub enum DataStoreError {

+//!     /// data store disconnected

+//!     Disconnect(#[source] io::Error),

+//!     /// the data for key `{0}` is not available

+//!     Redaction(String),

+//!     /// invalid header (expected {expected:?}, found {found:?})

+//!     InvalidHeader {

+//!         expected: String,

+//!         found: String,

+//!     },

+//!     /// unknown data store error

+//!     Unknown,

+//! }

+//!

+//! let error = DataStoreError::Redaction("CLASSIFIED CONTENT".to_string());

+//! assert!("the data for key `CLASSIFIED CONTENT` is not available" == &format!("{}", error));

+//! ```

+//! *Note that although [`io::Error`][std::io::Error] implements `Display`, we do not add it to the

+//! generated message for `DataStoreError::Disconnect`, since it is already made available via

+//! `#[source]`. See further context on avoiding duplication in error reports at the rust blog

+//! [here](https://github.com/yaahc/blog.rust-lang.org/blob/master/posts/inside-rust/2021-05-15-What-the-error-handling-project-group-is-working-towards.md#duplicate-information-issue).*

+//!

+//! <br>

+//!

+//! ## Details

+//!

+//! - A `fmt::Display` impl is generated for your enum if you provide

+//!   a docstring comment on each variant as shown above in the example. The

+//!   `Display` derive macro supports a shorthand for interpolating fields from

+//!   the error:

+//!     - `/// {var}` ⟶ `write!("{}", self.var)`

+//!     - `/// {0}` ⟶ `write!("{}", self.0)`

+//!     - `/// {var:?}` ⟶ `write!("{:?}", self.var)`

+//!     - `/// {0:?}` ⟶ `write!("{:?}", self.0)`

+//! - This also works with structs and [generic types][crate::Display#generic-type-parameters]:

+//! ```rust

+//! # use displaydoc::Display;

+//! /// oh no, an error: {0}

+//! #[derive(Display)]

+//! pub struct Error<E>(pub E);

+//!

+//! let error: Error<&str> = Error("muahaha i am an error");

+//! assert!("oh no, an error: muahaha i am an error" == &format!("{}", error));

+//! ```

+//!

+//! - Two optional attributes can be added to your types next to the derive:

+//!

+//!     - `#[ignore_extra_doc_attributes]` makes the macro ignore any doc

+//!       comment attributes (or `///` lines) after the first. Multi-line

+//!       comments using `///` are otherwise treated as an error, so use this

+//!       attribute or consider switching to block doc comments (`/** */`).

+//!

+//!     - `#[prefix_enum_doc_attributes]` combines the doc comment message on

+//!       your enum itself with the messages for each variant, in the format

+//!       “enum: variant”. When added to an enum, the doc comment on the enum

+//!       becomes mandatory. When added to any other type, it has no effect.

+//!

+//! - In case you want to have an independent doc comment, the

+//!   `#[displaydoc("...")` atrribute may be used on the variant or struct to

+//!   override it.

+//!

+//! <br>

+//!

+//! ## FAQ

+//!

+//! 1. **Is this crate `no_std` compatible?**

+//!     * Yes! This crate implements the [`core::fmt::Display`] trait, not the [`std::fmt::Display`] trait, so it should work in `std` and `no_std` environments. Just add `default-features = false`.

+//!

+//! 2. **Does this crate work with `Path` and `PathBuf` via the `Display` trait?**

+//!     * Yuuup. This crate uses @dtolnay's [autoref specialization technique](https://github.com/dtolnay/case-studies/blob/master/autoref-specialization/README.md) to add a special trait for types to get the display impl. It then specializes for `Path` and `PathBuf`, and when either of these types are found, it calls `self.display()` to get a `std::path::Display<'_>` type which can be used with the `Display` format specifier!

+#![doc(html_root_url = "https://docs.rs/displaydoc/0.2.3")]

+#![cfg_attr(docsrs, feature(doc_cfg))]

+#![warn(

+    rust_2018_idioms,

+    unreachable_pub,

+    bad_style,

+    dead_code,

+    improper_ctypes,

+    non_shorthand_field_patterns,

+    no_mangle_generic_items,

+    overflowing_literals,

+    path_statements,

+    patterns_in_fns_without_body,

+    private_in_public,

+    unconditional_recursion,

+    unused,

+    unused_allocation,

+    unused_comparisons,

+    unused_parens,

+    while_true

+)]

+#![allow(clippy::try_err)]

+

+#[allow(unused_extern_crates)]

+extern crate proc_macro;

+

+mod attr;

+mod expand;

+mod fmt;

+

+use proc_macro::TokenStream;

+use syn::{parse_macro_input, DeriveInput};

+

+/// [Custom `#[derive(...)]` macro](https://doc.rust-lang.org/edition-guide/rust-2018/macros/custom-derive.html)

+/// for implementing [`fmt::Display`][core::fmt::Display] via doc comment attributes.

+///

+/// ### Generic Type Parameters

+///

+/// Type parameters to an enum or struct using this macro should *not* need to

+/// have an explicit `Display` constraint at the struct or enum definition

+/// site. A `Display` implementation for the `derive`d struct or enum is

+/// generated assuming each type parameter implements `Display`, but that should

+/// be possible without adding the constraint to the struct definition itself:

+/// ```rust

+/// use displaydoc::Display;

+///

+/// /// oh no, an error: {0}

+/// #[derive(Display)]

+/// pub struct Error<E>(pub E);

+///

+/// // No need to require `E: Display`, since `displaydoc::Display` adds that implicitly.

+/// fn generate_error<E>(e: E) -> Error<E> { Error(e) }

+///

+/// assert!("oh no, an error: muahaha" == &format!("{}", generate_error("muahaha")));

+/// ```

+///

+/// ### Using [`Debug`][core::fmt::Debug] Implementations with Type Parameters

+/// However, if a type parameter must instead be constrained with the

+/// [`Debug`][core::fmt::Debug] trait so that some field may be printed with

+/// `{:?}`, that constraint must currently still also be specified redundantly

+/// at the struct or enum definition site. If a struct or enum field is being

+/// formatted with `{:?}` via [`displaydoc`][crate], and a generic type

+/// parameter must implement `Debug` to do that, then that struct or enum

+/// definition will need to propagate the `Debug` constraint to every type

+/// parameter it's instantiated with:

+/// ```rust

+/// use core::fmt::Debug;

+/// use displaydoc::Display;

+///

+/// /// oh no, an error: {0:?}

+/// #[derive(Display)]

+/// pub struct Error<E: Debug>(pub E);

+///

+/// // `E: Debug` now has to propagate to callers.

+/// fn generate_error<E: Debug>(e: E) -> Error<E> { Error(e) }

+///

+/// assert!("oh no, an error: \"cool\"" == &format!("{}", generate_error("cool")));

+///

+/// // Try this with a struct that doesn't impl `Display` at all, unlike `str`.

+/// #[derive(Debug)]

+/// pub struct Oh;

+/// assert!("oh no, an error: Oh" == &format!("{}", generate_error(Oh)));

+/// ```

+#[proc_macro_derive(

+    Display,

+    attributes(ignore_extra_doc_attributes, prefix_enum_doc_attributes, displaydoc)

+)]

+pub fn derive_error(input: TokenStream) -> TokenStream {

+    let input = parse_macro_input!(input as DeriveInput);

+    expand::derive(&input)

+        .unwrap_or_else(|err| err.to_compile_error())

+        .into()

+}