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use fxhash::FxHashMap;
use rnode::{Fold, FoldWith};
use stc_ts_types::{Id, Type};

#[derive(Debug)]
pub struct TypeParamReplacer {
    pub inferred: FxHashMap<Id, Type>,
    /// `true` means we should replace type parameters with other type
    /// parameter.
    pub include_type_params: bool,
}

impl Fold<Type> for TypeParamReplacer {
    fn fold(&mut self, mut ty: Type) -> Type {
        ty = ty.fold_children_with(self);

        if let Type::Param(ref param) = ty.normalize() {
            if let Some(mapped) = self.inferred.get(&param.name) {
                match mapped.normalize() {
                    Type::Param(..) if !self.include_type_params => return ty,
                    _ => {}
                }
                return mapped.clone();
            }
        }

        ty
    }
}