Merge commit '6eba9cd92c295c5389944f6adda1f1e83b2cb008' as 'subprojects/thiserror'

subprojects/thiserror/impl/src/expand.rs

@@ -0,0 +1,584 @@
+use crate::ast::{Enum, Field, Input, Struct};
+use crate::attr::Trait;
+use crate::fallback;
+use crate::generics::InferredBounds;
+use crate::private;
+use crate::unraw::MemberUnraw;
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use std::collections::BTreeSet as Set;
+use syn::{DeriveInput, GenericArgument, PathArguments, Result, Token, Type};
+
+pub fn derive(input: &DeriveInput) -> TokenStream {
+    match try_expand(input) {
+        Ok(expanded) => expanded,
+        // If there are invalid attributes in the input, expand to an Error impl
+        // anyway to minimize spurious secondary errors in other code that uses
+        // this type as an Error.
+        Err(error) => fallback::expand(input, error),
+    }
+}
+
+fn try_expand(input: &DeriveInput) -> Result<TokenStream> {
+    let input = Input::from_syn(input)?;
+    input.validate()?;
+    Ok(match input {
+        Input::Struct(input) => impl_struct(input),
+        Input::Enum(input) => impl_enum(input),
+    })
+}
+
+fn impl_struct(input: Struct) -> TokenStream {
+    let ty = call_site_ident(&input.ident);
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let mut error_inferred_bounds = InferredBounds::new();
+
+    let source_body = if let Some(transparent_attr) = &input.attrs.transparent {
+        let only_field = &input.fields[0];
+        if only_field.contains_generic {
+            error_inferred_bounds.insert(only_field.ty, quote!(::thiserror::#private::Error));
+        }
+        let member = &only_field.member;
+        Some(quote_spanned! {transparent_attr.span=>
+            ::thiserror::#private::Error::source(self.#member.as_dyn_error())
+        })
+    } else if let Some(source_field) = input.source_field() {
+        let source = &source_field.member;
+        if source_field.contains_generic {
+            let ty = unoptional_type(source_field.ty);
+            error_inferred_bounds.insert(ty, quote!(::thiserror::#private::Error + 'static));
+        }
+        let asref = if type_is_option(source_field.ty) {
+            Some(quote_spanned!(source.span()=> .as_ref()?))
+        } else {
+            None
+        };
+        let dyn_error = quote_spanned! {source_field.source_span()=>
+            self.#source #asref.as_dyn_error()
+        };
+        Some(quote! {
+            ::core::option::Option::Some(#dyn_error)
+        })
+    } else {
+        None
+    };
+    let source_method = source_body.map(|body| {
+        quote! {
+            fn source(&self) -> ::core::option::Option<&(dyn ::thiserror::#private::Error + 'static)> {
+                use ::thiserror::#private::AsDynError as _;
+                #body
+            }
+        }
+    });
+
+    let provide_method = input.backtrace_field().map(|backtrace_field| {
+        let request = quote!(request);
+        let backtrace = &backtrace_field.member;
+        let body = if let Some(source_field) = input.source_field() {
+            let source = &source_field.member;
+            let source_provide = if type_is_option(source_field.ty) {
+                quote_spanned! {source.span()=>
+                    if let ::core::option::Option::Some(source) = &self.#source {
+                        source.thiserror_provide(#request);
+                    }
+                }
+            } else {
+                quote_spanned! {source.span()=>
+                    self.#source.thiserror_provide(#request);
+                }
+            };
+            let self_provide = if source == backtrace {
+                None
+            } else if type_is_option(backtrace_field.ty) {
+                Some(quote! {
+                    if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
+                        #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                    }
+                })
+            } else {
+                Some(quote! {
+                    #request.provide_ref::<::thiserror::#private::Backtrace>(&self.#backtrace);
+                })
+            };
+            quote! {
+                use ::thiserror::#private::ThiserrorProvide as _;
+                #source_provide
+                #self_provide
+            }
+        } else if type_is_option(backtrace_field.ty) {
+            quote! {
+                if let ::core::option::Option::Some(backtrace) = &self.#backtrace {
+                    #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                }
+            }
+        } else {
+            quote! {
+                #request.provide_ref::<::thiserror::#private::Backtrace>(&self.#backtrace);
+            }
+        };
+        quote! {
+            fn provide<'_request>(&'_request self, #request: &mut ::core::error::Request<'_request>) {
+                #body
+            }
+        }
+    });
+
+    let mut display_implied_bounds = Set::new();
+    let display_body = if input.attrs.transparent.is_some() {
+        let only_field = &input.fields[0].member;
+        display_implied_bounds.insert((0, Trait::Display));
+        Some(quote! {
+            ::core::fmt::Display::fmt(&self.#only_field, __formatter)
+        })
+    } else if let Some(display) = &input.attrs.display {
+        display_implied_bounds.clone_from(&display.implied_bounds);
+        let use_as_display = use_as_display(display.has_bonus_display);
+        let pat = fields_pat(&input.fields);
+        Some(quote! {
+            #use_as_display
+            #[allow(unused_variables, deprecated)]
+            let Self #pat = self;
+            #display
+        })
+    } else {
+        None
+    };
+    let display_impl = display_body.map(|body| {
+        let mut display_inferred_bounds = InferredBounds::new();
+        for (field, bound) in display_implied_bounds {
+            let field = &input.fields[field];
+            if field.contains_generic {
+                display_inferred_bounds.insert(field.ty, bound);
+            }
+        }
+        let display_where_clause = display_inferred_bounds.augment_where_clause(input.generics);
+        quote! {
+            #[allow(unused_qualifications)]
+            #[automatically_derived]
+            impl #impl_generics ::core::fmt::Display for #ty #ty_generics #display_where_clause {
+                #[allow(clippy::used_underscore_binding)]
+                fn fmt(&self, __formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                    #body
+                }
+            }
+        }
+    });
+
+    let from_impl = input.from_field().map(|from_field| {
+        let span = from_field.attrs.from.unwrap().span;
+        let backtrace_field = input.distinct_backtrace_field();
+        let from = unoptional_type(from_field.ty);
+        let source_var = Ident::new("source", span);
+        let body = from_initializer(from_field, backtrace_field, &source_var);
+        let from_function = quote! {
+            fn from(#source_var: #from) -> Self {
+                #ty #body
+            }
+        };
+        let from_impl = quote_spanned! {span=>
+            #[automatically_derived]
+            impl #impl_generics ::core::convert::From<#from> for #ty #ty_generics #where_clause {
+                #from_function
+            }
+        };
+        Some(quote! {
+            #[allow(
+                deprecated,
+                unused_qualifications,
+                clippy::elidable_lifetime_names,
+                clippy::needless_lifetimes,
+            )]
+            #from_impl
+        })
+    });
+
+    if input.generics.type_params().next().is_some() {
+        let self_token = <Token![Self]>::default();
+        error_inferred_bounds.insert(self_token, Trait::Debug);
+        error_inferred_bounds.insert(self_token, Trait::Display);
+    }
+    let error_where_clause = error_inferred_bounds.augment_where_clause(input.generics);
+
+    quote! {
+        #[allow(unused_qualifications)]
+        #[automatically_derived]
+        impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #error_where_clause {
+            #source_method
+            #provide_method
+        }
+        #display_impl
+        #from_impl
+    }
+}
+
+fn impl_enum(input: Enum) -> TokenStream {
+    let ty = call_site_ident(&input.ident);
+    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
+    let mut error_inferred_bounds = InferredBounds::new();
+
+    let source_method = if input.has_source() {
+        let arms = input.variants.iter().map(|variant| {
+            let ident = &variant.ident;
+            if let Some(transparent_attr) = &variant.attrs.transparent {
+                let only_field = &variant.fields[0];
+                if only_field.contains_generic {
+                    error_inferred_bounds.insert(only_field.ty, quote!(::thiserror::#private::Error));
+                }
+                let member = &only_field.member;
+                let source = quote_spanned! {transparent_attr.span=>
+                    ::thiserror::#private::Error::source(transparent.as_dyn_error())
+                };
+                quote! {
+                    #ty::#ident {#member: transparent} => #source,
+                }
+            } else if let Some(source_field) = variant.source_field() {
+                let source = &source_field.member;
+                if source_field.contains_generic {
+                    let ty = unoptional_type(source_field.ty);
+                    error_inferred_bounds.insert(ty, quote!(::thiserror::#private::Error + 'static));
+                }
+                let asref = if type_is_option(source_field.ty) {
+                    Some(quote_spanned!(source.span()=> .as_ref()?))
+                } else {
+                    None
+                };
+                let varsource = quote!(source);
+                let dyn_error = quote_spanned! {source_field.source_span()=>
+                    #varsource #asref.as_dyn_error()
+                };
+                quote! {
+                    #ty::#ident {#source: #varsource, ..} => ::core::option::Option::Some(#dyn_error),
+                }
+            } else {
+                quote! {
+                    #ty::#ident {..} => ::core::option::Option::None,
+                }
+            }
+        });
+        Some(quote! {
+            fn source(&self) -> ::core::option::Option<&(dyn ::thiserror::#private::Error + 'static)> {
+                use ::thiserror::#private::AsDynError as _;
+                #[allow(deprecated)]
+                match self {
+                    #(#arms)*
+                }
+            }
+        })
+    } else {
+        None
+    };
+
+    let provide_method = if input.has_backtrace() {
+        let request = quote!(request);
+        let arms = input.variants.iter().map(|variant| {
+            let ident = &variant.ident;
+            match (variant.backtrace_field(), variant.source_field()) {
+                (Some(backtrace_field), Some(source_field))
+                    if backtrace_field.attrs.backtrace.is_none() =>
+                {
+                    let backtrace = &backtrace_field.member;
+                    let source = &source_field.member;
+                    let varsource = quote!(source);
+                    let source_provide = if type_is_option(source_field.ty) {
+                        quote_spanned! {source.span()=>
+                            if let ::core::option::Option::Some(source) = #varsource {
+                                source.thiserror_provide(#request);
+                            }
+                        }
+                    } else {
+                        quote_spanned! {source.span()=>
+                            #varsource.thiserror_provide(#request);
+                        }
+                    };
+                    let self_provide = if type_is_option(backtrace_field.ty) {
+                        quote! {
+                            if let ::core::option::Option::Some(backtrace) = backtrace {
+                                #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                            }
+                        }
+                    } else {
+                        quote! {
+                            #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                        }
+                    };
+                    quote! {
+                        #ty::#ident {
+                            #backtrace: backtrace,
+                            #source: #varsource,
+                            ..
+                        } => {
+                            use ::thiserror::#private::ThiserrorProvide as _;
+                            #source_provide
+                            #self_provide
+                        }
+                    }
+                }
+                (Some(backtrace_field), Some(source_field))
+                    if backtrace_field.member == source_field.member =>
+                {
+                    let backtrace = &backtrace_field.member;
+                    let varsource = quote!(source);
+                    let source_provide = if type_is_option(source_field.ty) {
+                        quote_spanned! {backtrace.span()=>
+                            if let ::core::option::Option::Some(source) = #varsource {
+                                source.thiserror_provide(#request);
+                            }
+                        }
+                    } else {
+                        quote_spanned! {backtrace.span()=>
+                            #varsource.thiserror_provide(#request);
+                        }
+                    };
+                    quote! {
+                        #ty::#ident {#backtrace: #varsource, ..} => {
+                            use ::thiserror::#private::ThiserrorProvide as _;
+                            #source_provide
+                        }
+                    }
+                }
+                (Some(backtrace_field), _) => {
+                    let backtrace = &backtrace_field.member;
+                    let body = if type_is_option(backtrace_field.ty) {
+                        quote! {
+                            if let ::core::option::Option::Some(backtrace) = backtrace {
+                                #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                            }
+                        }
+                    } else {
+                        quote! {
+                            #request.provide_ref::<::thiserror::#private::Backtrace>(backtrace);
+                        }
+                    };
+                    quote! {
+                        #ty::#ident {#backtrace: backtrace, ..} => {
+                            #body
+                        }
+                    }
+                }
+                (None, _) => quote! {
+                    #ty::#ident {..} => {}
+                },
+            }
+        });
+        Some(quote! {
+            fn provide<'_request>(&'_request self, #request: &mut ::core::error::Request<'_request>) {
+                #[allow(deprecated)]
+                match self {
+                    #(#arms)*
+                }
+            }
+        })
+    } else {
+        None
+    };
+
+    let display_impl = if input.has_display() {
+        let mut display_inferred_bounds = InferredBounds::new();
+        let has_bonus_display = input.variants.iter().any(|v| {
+            v.attrs
+                .display
+                .as_ref()
+                .map_or(false, |display| display.has_bonus_display)
+        });
+        let use_as_display = use_as_display(has_bonus_display);
+        let void_deref = if input.variants.is_empty() {
+            Some(quote!(*))
+        } else {
+            None
+        };
+        let arms = input.variants.iter().map(|variant| {
+            let mut display_implied_bounds = Set::new();
+            let display = if let Some(display) = &variant.attrs.display {
+                display_implied_bounds.clone_from(&display.implied_bounds);
+                display.to_token_stream()
+            } else if let Some(fmt) = &variant.attrs.fmt {
+                let fmt_path = &fmt.path;
+                let vars = variant.fields.iter().map(|field| match &field.member {
+                    MemberUnraw::Named(ident) => ident.to_local(),
+                    MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                });
+                quote!(#fmt_path(#(#vars,)* __formatter))
+            } else {
+                let only_field = match &variant.fields[0].member {
+                    MemberUnraw::Named(ident) => ident.to_local(),
+                    MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                };
+                display_implied_bounds.insert((0, Trait::Display));
+                quote!(::core::fmt::Display::fmt(#only_field, __formatter))
+            };
+            for (field, bound) in display_implied_bounds {
+                let field = &variant.fields[field];
+                if field.contains_generic {
+                    display_inferred_bounds.insert(field.ty, bound);
+                }
+            }
+            let ident = &variant.ident;
+            let pat = fields_pat(&variant.fields);
+            quote! {
+                #ty::#ident #pat => #display
+            }
+        });
+        let arms = arms.collect::<Vec<_>>();
+        let display_where_clause = display_inferred_bounds.augment_where_clause(input.generics);
+        Some(quote! {
+            #[allow(unused_qualifications)]
+            #[automatically_derived]
+            impl #impl_generics ::core::fmt::Display for #ty #ty_generics #display_where_clause {
+                fn fmt(&self, __formatter: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+                    #use_as_display
+                    #[allow(unused_variables, deprecated, clippy::used_underscore_binding)]
+                    match #void_deref self {
+                        #(#arms,)*
+                    }
+                }
+            }
+        })
+    } else {
+        None
+    };
+
+    let from_impls = input.variants.iter().filter_map(|variant| {
+        let from_field = variant.from_field()?;
+        let span = from_field.attrs.from.unwrap().span;
+        let backtrace_field = variant.distinct_backtrace_field();
+        let variant = &variant.ident;
+        let from = unoptional_type(from_field.ty);
+        let source_var = Ident::new("source", span);
+        let body = from_initializer(from_field, backtrace_field, &source_var);
+        let from_function = quote! {
+            fn from(#source_var: #from) -> Self {
+                #ty::#variant #body
+            }
+        };
+        let from_impl = quote_spanned! {span=>
+            #[automatically_derived]
+            impl #impl_generics ::core::convert::From<#from> for #ty #ty_generics #where_clause {
+                #from_function
+            }
+        };
+        Some(quote! {
+            #[allow(
+                deprecated,
+                unused_qualifications,
+                clippy::elidable_lifetime_names,
+                clippy::needless_lifetimes,
+            )]
+            #from_impl
+        })
+    });
+
+    if input.generics.type_params().next().is_some() {
+        let self_token = <Token![Self]>::default();
+        error_inferred_bounds.insert(self_token, Trait::Debug);
+        error_inferred_bounds.insert(self_token, Trait::Display);
+    }
+    let error_where_clause = error_inferred_bounds.augment_where_clause(input.generics);
+
+    quote! {
+        #[allow(unused_qualifications)]
+        #[automatically_derived]
+        impl #impl_generics ::thiserror::#private::Error for #ty #ty_generics #error_where_clause {
+            #source_method
+            #provide_method
+        }
+        #display_impl
+        #(#from_impls)*
+    }
+}
+
+// Create an ident with which we can expand `impl Trait for #ident {}` on a
+// deprecated type without triggering deprecation warning on the generated impl.
+pub(crate) fn call_site_ident(ident: &Ident) -> Ident {
+    let mut ident = ident.clone();
+    ident.set_span(ident.span().resolved_at(Span::call_site()));
+    ident
+}
+
+fn fields_pat(fields: &[Field]) -> TokenStream {
+    let mut members = fields.iter().map(|field| &field.member).peekable();
+    match members.peek() {
+        Some(MemberUnraw::Named(_)) => quote!({ #(#members),* }),
+        Some(MemberUnraw::Unnamed(_)) => {
+            let vars = members.map(|member| match member {
+                MemberUnraw::Unnamed(index) => format_ident!("_{}", index),
+                MemberUnraw::Named(_) => unreachable!(),
+            });
+            quote!((#(#vars),*))
+        }
+        None => quote!({}),
+    }
+}
+
+fn use_as_display(needs_as_display: bool) -> Option<TokenStream> {
+    if needs_as_display {
+        Some(quote! {
+            use ::thiserror::#private::AsDisplay as _;
+        })
+    } else {
+        None
+    }
+}
+
+fn from_initializer(
+    from_field: &Field,
+    backtrace_field: Option<&Field>,
+    source_var: &Ident,
+) -> TokenStream {
+    let from_member = &from_field.member;
+    let some_source = if type_is_option(from_field.ty) {
+        quote!(::core::option::Option::Some(#source_var))
+    } else {
+        quote!(#source_var)
+    };
+    let backtrace = backtrace_field.map(|backtrace_field| {
+        let backtrace_member = &backtrace_field.member;
+        if type_is_option(backtrace_field.ty) {
+            quote! {
+                #backtrace_member: ::core::option::Option::Some(::thiserror::#private::Backtrace::capture()),
+            }
+        } else {
+            quote! {
+                #backtrace_member: ::core::convert::From::from(::thiserror::#private::Backtrace::capture()),
+            }
+        }
+    });
+    quote!({
+        #from_member: #some_source,
+        #backtrace
+    })
+}
+
+fn type_is_option(ty: &Type) -> bool {
+    type_parameter_of_option(ty).is_some()
+}
+
+fn unoptional_type(ty: &Type) -> TokenStream {
+    let unoptional = type_parameter_of_option(ty).unwrap_or(ty);
+    quote!(#unoptional)
+}
+
+fn type_parameter_of_option(ty: &Type) -> Option<&Type> {
+    let path = match ty {
+        Type::Path(ty) => &ty.path,
+        _ => return None,
+    };
+
+    let last = path.segments.last().unwrap();
+    if last.ident != "Option" {
+        return None;
+    }
+
+    let bracketed = match &last.arguments {
+        PathArguments::AngleBracketed(bracketed) => bracketed,
+        _ => return None,
+    };
+
+    if bracketed.args.len() != 1 {
+        return None;
+    }
+
+    match &bracketed.args[0] {
+        GenericArgument::Type(arg) => Some(arg),
+        _ => None,
+    }
+}