Why is TyCtxt required for borrow checking?

compiler
1

I’m studying rustc and am currently looking into the rustc_borrowck crate. I noticed that the mir_borrowck function takes a TyCtxt object as an argument. Likewise, the do_mir_borrowck function receives a BorrowCheckRootCtxt, which also contains a TyCtxt.

Why does the borrow-checker need access to a TyCtxt? Isn’t it possible to perform borrow checking using only the MIR body (Body) of the function being checked?

2

Borrow checking needs to invoke the trait solver among other things, which needs the TyCtxt.

3

Thank you for your reply!

If I understand your comment correctly, TyCtxt is required for MIR typeck, right? Do you know why this type checking is performed inside the mir_borrowck function? I am interested in the reason why borrowck is not defined only for the MIR body.

4

Borrowck does MIR typeck to collect all outlives constraints between lifetimes. Among other things borrowck checks if all outlives constraints are satisfiable.

5

I see. Thank you very much!