Possible typo in ProgrammersManual documentation

[sanjoy]

I'm not sure that this is a typo -- the existing doc is probably talking about the shapes of the struct and array types.

[singam-sanjay]

The novice reader would associate shape with only two of the DerivedTypes: VectorType and ArrayType. How could a FunctionType or an IntegerType have a shape ?

In D33332#789882, @sanjoy wrote:

I'm not sure that this is a typo -- the existing doc is probably talking about the shapes of the struct and array types.

Also, I didn't understand what was meant by a struct having a shape.

I raised this patch because I had misinterpreted it the first time I read it.

[sanjoy]

In D33332#848836, @singam-sanjay wrote:

The novice reader would associate shape with only two of the DerivedTypes: VectorType and ArrayType. How could a FunctionType or an IntegerType have a shape ?

In D33332#789882, @sanjoy wrote:

I'm not sure that this is a typo -- the existing doc is probably talking about the shapes of the struct and array types.

Also, I didn't understand what was meant by a struct having a shape.

I raised this patch because I had misinterpreted it the first time I read it.

I see. My problem was that "There exists exactly one instance of a given Type at any one time." sounds like a circular statement. How about "Types in LLVM are interned, and this means pointer equality is the same as type equality".

docs/ProgrammersManual.rst

 ``Type`` is a superclass of all type classes.  Every ``Value`` has a ``Type``.
 ``Type`` cannot be instantiated directly but only through its subclasses.
 Certain primitive types (``VoidType``, ``LabelType``, ``FloatType`` and
 ``DoubleType``) have hidden subclasses.  They are hidden because they offer no
 useful functionality beyond what the ``Type`` class offers except to distinguish
 themselves from other subclasses of ``Type``.
 
 All other types are subclasses of ``DerivedType``.  Types can be named, but this
-is not a requirement.  There exists exactly one instance of a given shape at any
+is not a requirement.  There exists exactly one instance of a given Type at any
 one time.  This allows type equality to be performed with address equality of
 the Type Instance.  That is, given two ``Type*`` values, the types are identical
 if the pointers are identical.
 
 .. _m_Type:
 
 Important Public Methods
 ^^^^^^^^^^^^^^^^^^^^^^^^