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Diffstat (limited to 'docs/design/casting.md')
| -rw-r--r-- | docs/design/casting.md | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/docs/design/casting.md b/docs/design/casting.md index 522e1d707..6c4b119eb 100644 --- a/docs/design/casting.md +++ b/docs/design/casting.md @@ -7,7 +7,7 @@ C++'s built in mechanisms for casting (principally dynamic_cast) is problematic * There are types which we want to 'dynamic_cast' that do not have, and we do not want to have a Vtbl (for example Slang::IRInst). * There are types which a 'dynamic_cast' doesn't do quite what we want (for example casting on Type* derived types typically wants to work on their canonical type) -* We may want to replace use of dynamic_cast in the future for speed/space or other reasons in the future +* We may want to replace use of dynamic_cast in the future for speed/space or other reasons * It is common in the code base when using a 'smart pointer' type to cast it, but still return a smart pointer To deal with these issues we need casting within Slang to follow it's own methodology. In summary it is as follows... @@ -18,6 +18,8 @@ To deal with these issues we need casting within Slang to follow it's own method * If you want to *literally* do a dynamic cast use 'dynamicCast' free function. * This guarantees the returned pointer points to the same object (like normal dynamic_cast) * If you want to return a smart pointer from a cast from a smart pointer use the .as or .dynamicCast *methods* +* If you want to determine if an 'as' cast is possible on a smart pointer use the .is method + * Doing so will produce more efficient code because a new smart pointer does not need to be constructed These functions will also work with types that do not have Vtbl - like IRInst derived types. |