RE: [sv-bc] implicit casts

Hi, 

> "The existence of casts may enable tools to perform stronger 
> type checking, by providing a mechanism for users to suppress 
> that type checking when desired."

This enables detection of inadvertent type conversion by letting the
user tag deliberate type conversion.

A similar idea is in size-extension. SV has implicit size-extension, but
it can hide errors. For example, if one wrote

a[15:0] = b[16:2]; // LHS = 16 bits, RHS = 15 bits

it is likely that this is an error, and the RHS was supposed to be
either b[16:1] or b[17:2]. By requiring explicit size-extension, such as
{1'b0, b[16:2]}, when one really wants it, this allows detection of
likely errors by implicit size-extension. Otherwise, the implicit
size-extension errors are swamped by the 99% of cases which are not
errors.

By the way, in a similar case I had years ago, the RHS which was really
desired was of the form {b[16:2], 1'b0}.

None of this answers my original question, though. I don't find implicit
casting really described in 6.24.

Shalom

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