The meaning of
typedef is defined in the standard at n1256 S6.7.7. It says:
A typedef declaration does not introduce a new type, only a
synonym for the type so specified.
In other words, a typedef is complete and meaningful as soon as the declaration is complete. Nothing is left to be analysed later.
Although giving things meanings is part of semantic analysis, this particular action must take place during syntactic analysis, because this information is used later to choose between possibly ambiguous syntactic interpretations. For example S6.7.3:
If the same qualifier appears more than once in the same specifier-qualifier-list, either
directly or via one or more typedefs, the behavior is the same as if it appeared only
So the answer is: during syntax analysis, with the reservation that this might be taken to overlap with semantic analysis.