New upstream version 1.52.1+dfsg1

[rustc.git] / vendor / thiserror-impl / src / attr.rs

diff --git a/vendor/thiserror-impl/src/attr.rs b/vendor/thiserror-impl/src/attr.rs
new file mode 100644 (file)
index 0000000..1ab1e28
--- /dev/null
+++ b/vendor/thiserror-impl/src/attr.rs
@@ -0,0 +1,190 @@
+use proc_macro2::{Delimiter, Group, Span, TokenStream, TokenTree};
+use quote::{format_ident, quote, ToTokens};
+use std::iter::FromIterator;
+use syn::parse::{Nothing, ParseStream};
+use syn::{
+    braced, bracketed, parenthesized, token, Attribute, Error, Ident, Index, LitInt, LitStr,
+    Result, Token,
+};
+
+pub struct Attrs<'a> {
+    pub display: Option<Display<'a>>,
+    pub source: Option<&'a Attribute>,
+    pub backtrace: Option<&'a Attribute>,
+    pub from: Option<&'a Attribute>,
+    pub transparent: Option<Transparent<'a>>,
+}
+
+#[derive(Clone)]
+pub struct Display<'a> {
+    pub original: &'a Attribute,
+    pub fmt: LitStr,
+    pub args: TokenStream,
+    pub has_bonus_display: bool,
+}
+
+#[derive(Copy, Clone)]
+pub struct Transparent<'a> {
+    pub original: &'a Attribute,
+    pub span: Span,
+}
+
+pub fn get(input: &[Attribute]) -> Result<Attrs> {
+    let mut attrs = Attrs {
+        display: None,
+        source: None,
+        backtrace: None,
+        from: None,
+        transparent: None,
+    };
+
+    for attr in input {
+        if attr.path.is_ident("error") {
+            parse_error_attribute(&mut attrs, attr)?;
+        } else if attr.path.is_ident("source") {
+            require_empty_attribute(attr)?;
+            if attrs.source.is_some() {
+                return Err(Error::new_spanned(attr, "duplicate #[source] attribute"));
+            }
+            attrs.source = Some(attr);
+        } else if attr.path.is_ident("backtrace") {
+            require_empty_attribute(attr)?;
+            if attrs.backtrace.is_some() {
+                return Err(Error::new_spanned(attr, "duplicate #[backtrace] attribute"));
+            }
+            attrs.backtrace = Some(attr);
+        } else if attr.path.is_ident("from") {
+            if !attr.tokens.is_empty() {
+                // Assume this is meant for derive_more crate or something.
+                continue;
+            }
+            if attrs.from.is_some() {
+                return Err(Error::new_spanned(attr, "duplicate #[from] attribute"));
+            }
+            attrs.from = Some(attr);
+        }
+    }
+
+    Ok(attrs)
+}
+
+fn parse_error_attribute<'a>(attrs: &mut Attrs<'a>, attr: &'a Attribute) -> Result<()> {
+    syn::custom_keyword!(transparent);
+
+    attr.parse_args_with(|input: ParseStream| {
+        if let Some(kw) = input.parse::<Option<transparent>>()? {
+            if attrs.transparent.is_some() {
+                return Err(Error::new_spanned(
+                    attr,
+                    "duplicate #[error(transparent)] attribute",
+                ));
+            }
+            attrs.transparent = Some(Transparent {
+                original: attr,
+                span: kw.span,
+            });
+            return Ok(());
+        }
+
+        let display = Display {
+            original: attr,
+            fmt: input.parse()?,
+            args: parse_token_expr(input, false)?,
+            has_bonus_display: false,
+        };
+        if attrs.display.is_some() {
+            return Err(Error::new_spanned(
+                attr,
+                "only one #[error(...)] attribute is allowed",
+            ));
+        }
+        attrs.display = Some(display);
+        Ok(())
+    })
+}
+
+fn parse_token_expr(input: ParseStream, mut begin_expr: bool) -> Result<TokenStream> {
+    let mut tokens = Vec::new();
+    while !input.is_empty() {
+        if begin_expr && input.peek(Token![.]) {
+            if input.peek2(Ident) {
+                input.parse::<Token![.]>()?;
+                begin_expr = false;
+                continue;
+            }
+            if input.peek2(LitInt) {
+                input.parse::<Token![.]>()?;
+                let int: Index = input.parse()?;
+                let ident = format_ident!("_{}", int.index, span = int.span);
+                tokens.push(TokenTree::Ident(ident));
+                begin_expr = false;
+                continue;
+            }
+        }
+
+        begin_expr = input.peek(Token![break])
+            || input.peek(Token![continue])
+            || input.peek(Token![if])
+            || input.peek(Token![in])
+            || input.peek(Token![match])
+            || input.peek(Token![mut])
+            || input.peek(Token![return])
+            || input.peek(Token![while])
+            || input.peek(Token![+])
+            || input.peek(Token![&])
+            || input.peek(Token![!])
+            || input.peek(Token![^])
+            || input.peek(Token![,])
+            || input.peek(Token![/])
+            || input.peek(Token![=])
+            || input.peek(Token![>])
+            || input.peek(Token![<])
+            || input.peek(Token![|])
+            || input.peek(Token![%])
+            || input.peek(Token![;])
+            || input.peek(Token![*])
+            || input.peek(Token![-]);
+
+        let token: TokenTree = if input.peek(token::Paren) {
+            let content;
+            let delimiter = parenthesized!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Parenthesis, nested);
+            group.set_span(delimiter.span);
+            TokenTree::Group(group)
+        } else if input.peek(token::Brace) {
+            let content;
+            let delimiter = braced!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Brace, nested);
+            group.set_span(delimiter.span);
+            TokenTree::Group(group)
+        } else if input.peek(token::Bracket) {
+            let content;
+            let delimiter = bracketed!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Bracket, nested);
+            group.set_span(delimiter.span);
+            TokenTree::Group(group)
+        } else {
+            input.parse()?
+        };
+        tokens.push(token);
+    }
+    Ok(TokenStream::from_iter(tokens))
+}
+
+fn require_empty_attribute(attr: &Attribute) -> Result<()> {
+    syn::parse2::<Nothing>(attr.tokens.clone())?;
+    Ok(())
+}
+
+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)
+        });
+    }
+}