Merge new reinterpret with essentials.jl reinterpret

base/essentials.jl

@@ -543,21 +543,41 @@ unsafe_convert(::Type{T}, x::T) where {T<:Ptr} = x  # to resolve ambiguity with
 unsafe_convert(::Type{P}, x::Ptr) where {P<:Ptr} = convert(P, x)
 
 """
-    reinterpret(type, x)
+    reinterpret(::Type{Out}, x::In)
 
-Change the type-interpretation of the binary data in the primitive value `x`
-to that of the primitive type `type`.
-The size of `type` has to be the same as that of the type of `x`.
+Change the type-interpretation of the binary data in the isbits value `x`
+to that of the isbits type `type`.
+The size (ignoring padding) of `type` has to be the same as that of the type of `x`.
 For example, `reinterpret(Float32, UInt32(7))` interprets the 4 bytes corresponding to `UInt32(7)` as a
 [`Float32`](@ref).
 
-# Examples
 ```jldoctest
 julia> reinterpret(Float32, UInt32(7))
 1.0f-44
+
+julia> reinterpret(NTuple{2, UInt8}, 0x1234)
+(0x34, 0x12)
+
+julia> reinterpret(UInt16, (0x34, 0x12))
+0x1234
+
+julia> reinterpret(Tuple{UInt16, UInt8}, (0x01, 0x0203))
+(0x0301, 0x02)
 ```
+
+!!! warning
+
+    Use caution if some combinations of bits in `Out` are not considered valid and would
+    otherwise be prevented by the type's constructors and methods. Unexpected behavior
+    may result without additional validation.
 """
-reinterpret(::Type{T}, x) where {T} = bitcast(T, x)
+function reinterpret(Out::Type, x::In) where {In}
+    if isprimitivetype(Out) && isprimitivetype(In)
+        return bitcast(Out, x)
+    end
+    # only available when Base is fully loaded.
+    return _reinterpret(Out, x)
+end
 
 """
     sizeof(T::DataType)

base/reinterpretarray.jl

@@ -795,42 +795,10 @@ function _copyfrompacked!(ptr_out::Ptr{Out}, ptr_in::Ptr{In}) where {Out, In}
     end
 end
 
-"""
-    reinterpret(::Type{Out}, x::In)
-
-Reinterpret the valid non-padding bytes of an isbits value `x` as isbits type `Out`.
-
-Both types must have the same amount of non-padding bytes. This operation is guaranteed
-to be reversible.
-
-```jldoctest
-julia> reinterpret(NTuple{2, UInt8}, 0x1234)
-(0x34, 0x12)
-
-julia> reinterpret(UInt16, (0x34, 0x12))
-0x1234
-
-julia> reinterpret(Tuple{UInt16, UInt8}, (0x01, 0x0203))
-(0x0301, 0x02)
-```
-
-!!! warning
-
-    Use caution if some combinations of bits in `Out` are not considered valid and would
-    otherwise be prevented by the type's constructors and methods. Unexpected behavior
-    may result without additional validation.
-"""
-@inline function reinterpret(::Type{Out}, x::In) where {Out, In}
+@inline function _reinterpret(::Type{Out}, x::In) where {Out, In}
+    # handle non-primitive types
     isbitstype(Out) || throw(ArgumentError("Target type for `reinterpret` must be isbits"))
     isbitstype(In) || throw(ArgumentError("Source type for `reinterpret` must be isbits"))
-    if isprimitivetype(Out) && isprimitivetype(In)
-        outsize = sizeof(Out)
-        insize = sizeof(In)
-        outsize == insize ||
-            throw(ArgumentError("Sizes of types $Out and $In do not match; got $outsize \
-                and $insize, respectively."))
-        return bitcast(Out, x)
-    end
     inpackedsize = packedsize(In)
     outpackedsize = packedsize(Out)
     inpackedsize == outpackedsize ||