Repository: pola-rs/polars
File: crates/polars-core/src/datatypes/dtype.rs (Rust)

Code before:
            // We don't allow the other way around, only if our current type is
            // null and the schema isn't we allow it.
            (DataType::Null, _) => Ok(true),
            (l, r) if l == r => Ok(false),
            (l, r) => {
                polars_bail!(SchemaMismatch: "type {:?} is incompatible with expected type {:?}", l, r)
            },
        }
    }

    #[inline]
    pub fn is_unknown(&self) -> bool {
        matches!(self, DataType::Unknown(_))
    }

    pub fn nesting_level(&self) -> usize {
        let mut level = 0;
        let mut slf = self;
        while let Some(inner_dtype) = slf.inner_dtype() {
            level += 1;
            slf = inner_dtype;
        }
        level
    }

    pub fn byte_size(&self) -> Option<usize> {
        match self {
            DataType::Boolean => None,
            DataType::UInt8 => Some(1),
            DataType::UInt16 => Some(2),
            DataType::UInt32 => Some(4),
            DataType::UInt64 => Some(8),
            DataType::Int8 => Some(1),
            DataType::Int16 => Some(2),
            DataType::Int32 => Some(4),
            DataType::Int64 => Some(8),
            DataType::Int128 => Some(16),
            DataType::Float32 => Some(4),
            DataType::Float64 => Some(8),
            #[cfg(feature = "dtype-decimal")]
            DataType::Decimal(_, _) => Some(16),
            DataType::String => None,
            DataType::Binary => None,
            DataType::BinaryOffset => None,
            DataType::Date => Some(4),
            DataType::Datetime(_, _) => Some(8),
            DataType::Duration(_) => Some(8),
            DataType::Time => Some(8),
            #[cfg(feature = "dtype-array")]
            DataType::Array(data_type, size) => data_type.byte_size().map(|v| v * size),
            DataType::List(_) => None,

Review comment (suggestion):
This function should be removed. From what I can see it's used in 2 places:
* In a `polars_ensure!` - it's enough to check that the inner type is a primitive type
* For `element_size`, you can get this from `std::mem::size_of::<T>()` inside the function instead of passing it in.


Code after:
    /// error is returned if the types are incompatible.
    pub fn matches_schema_type(&self, schema_type: &DataType) -> PolarsResult<bool> {
        match (self, schema_type) {
            (DataType::List(l), DataType::List(r)) => l.matches_schema_type(r),
            #[cfg(feature = "dtype-array")]
            (DataType::Array(l, sl), DataType::Array(r, sr)) => {
                Ok(l.matches_schema_type(r)? && sl == sr)
            },
            #[cfg(feature = "dtype-struct")]
            (DataType::Struct(l), DataType::Struct(r)) => {
                if l.len() != r.len() {
                    polars_bail!(SchemaMismatch: "structs have different number of fields: {} vs {}", l.len(), r.len());
                }
                let mut must_cast = false;
                for (l, r) in l.iter().zip(r.iter()) {
                    must_cast |= l.dtype.matches_schema_type(&r.dtype)?;
                }
                Ok(must_cast)
            },
            (DataType::Null, DataType::Null) => Ok(false),
            #[cfg(feature = "dtype-decimal")]
            (DataType::Decimal(_, s1), DataType::Decimal(_, s2)) => Ok(s1 != s2),
            // We don't allow the other way around, only if our current type is
            // null and the schema isn't we allow it.
            (DataType::Null, _) => Ok(true),
            #[cfg(feature = "dtype-categorical")]
            (DataType::Categorical(l, _), DataType::Categorical(r, _)) => {
                ensure_same_categories(l, r)?;
                Ok(false)
            },
            #[cfg(feature = "dtype-categorical")]
            (DataType::Enum(l, _), DataType::Enum(r, _)) => {
                ensure_same_frozen_categories(l, r)?;
                Ok(false)
            },

            (l, r) if l == r => Ok(false),
            (l, r) => {
                polars_bail!(SchemaMismatch: "type {:?} is incompatible with expected type {:?}", l, r)
            },
        }
    }

    #[inline]
    pub fn is_unknown(&self) -> bool {
        matches!(self, DataType::Unknown(_))
    }

    pub fn nesting_level(&self) -> usize {
        let mut level = 0;
        let mut slf = self;