educe 0.8.0

This crate offers procedural macros designed to facilitate the swift implementation of Rust's built-in traits.
Documentation 
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use quote::{ToTokens, quote};
use syn::{Expr, Lit, Meta, PathArguments, Type, TypePath};

use super::path::path_to_string;

const INT_TYPES: [&str; 12] =
    ["u8", "u16", "u32", "u64", "u128", "usize", "i8", "i16", "i32", "i64", "i128", "isize"];

const FLOAT_TYPES: [&str; 2] = ["f32", "f64"];

fn primitive_type_name(ty: &TypePath) -> String {
    let segments = &ty.path.segments;

    if ty.qself.is_none()
        && segments.len() == 3
        && (segments[0].ident == "core" || segments[0].ident == "std")
        && segments[1].ident == "primitive"
        && segments.iter().all(|segment| matches!(segment.arguments, PathArguments::None))
    {
        segments[2].ident.to_string()
    } else {
        ty.to_token_stream().to_string()
    }
}

#[inline]
pub(crate) fn meta_2_expr(meta: &Meta) -> syn::Result<Expr> {
    match &meta {
        Meta::NameValue(name_value) => Ok(name_value.value.clone()),
        Meta::List(list) => list.parse_args::<Expr>(),
        Meta::Path(path) => Err(syn::Error::new_spanned(
            path,
            format!("expected `{path} = Expr` or `{path}(Expr)`", path = path_to_string(path)),
        )),
    }
}

#[inline]
pub(crate) fn auto_adjust_expr(expr: Expr, ty: Option<&Type>) -> Expr {
    match &expr {
        Expr::Lit(lit) => {
            match &lit.lit {
                Lit::Int(lit) => {
                    if let Some(Type::Path(ty)) = ty {
                        let ty_string = primitive_type_name(ty);

                        if lit.suffix() == ty_string || INT_TYPES.contains(&ty_string.as_str()) {
                            // don't call into
                            return expr;
                        }
                    }
                },
                Lit::Float(lit) => {
                    if let Some(Type::Path(ty)) = ty {
                        let ty_string = primitive_type_name(ty);

                        if lit.suffix() == ty_string || FLOAT_TYPES.contains(&ty_string.as_str()) {
                            // don't call into
                            return expr;
                        }
                    }
                },
                Lit::Str(_) => {
                    if let Some(Type::Reference(ty)) = ty
                        && let Type::Path(ty) = ty.elem.as_ref()
                    {
                        let ty_string = primitive_type_name(ty);

                        if ty_string == "str" {
                            // don't call into
                            return expr;
                        }
                    }
                },
                Lit::Bool(_) => {
                    if let Some(Type::Path(ty)) = ty {
                        let ty_string = primitive_type_name(ty);

                        if ty_string == "bool" {
                            // don't call into
                            return expr;
                        }
                    }
                },
                Lit::Char(_) => {
                    if let Some(Type::Path(ty)) = ty {
                        let ty_string = primitive_type_name(ty);

                        if ty_string == "char" {
                            // don't call into
                            return expr;
                        }
                    }
                },
                Lit::Byte(_) => {
                    if let Some(Type::Path(ty)) = ty {
                        let ty_string = primitive_type_name(ty);

                        if ty_string == "u8" {
                            // don't call into
                            return expr;
                        }
                    }
                },
                Lit::ByteStr(_) => {
                    if let Some(Type::Reference(ty)) = ty
                        && let Type::Array(ty) = ty.elem.as_ref()
                        && let Type::Path(ty) = ty.elem.as_ref()
                    {
                        let ty_string = primitive_type_name(ty);

                        if ty_string == "u8" {
                            // don't call into
                            return expr;
                        }
                    }
                },
                _ => (),
            }

            syn::parse2(quote!(::core::convert::Into::into(#expr))).unwrap()
        },
        _ => expr,
    }
}