The purpose of the newline is to make it clearer where a given
diagnostic begins and ends, particularly as the first message of a
diagnostic may not be the error.
This is a trivial code change, but ripples edits through test files.
This is an incremental improvement on our diagnostic messages that
simply underlines an entire token if the token is larger than 1 char
(else it points to the single char with a caret like it used to).
This makes the difference between errors and lower-level diagnostics
visible to users, and aligns the toolchain's behavior with the
expectations in `driver_fuzzer.cpp`.
There were two issues contributing to this crash:
- Primarily, the issue is that we queue up diagnostics and don't format
them into a string until we reach the end of compilation. In some code
paths in the driver, we destroyed the Semantics IR object before this
happened. But diagnostics can contain references to Semantics IR
objects, such as strings stored in the string table, which can lead to a
use after destruction bug.
This is fixed by ensuring the diagnotics consumer is flushed before
destroying any of the objects that it can refer to. The current approach
to this is not especially clean, unfortunately, but this requires
fighting C++ as this isn't the order in which it wants to destroy
things.
- This issue was obscured by the Semantics IR's string table holding a
reference to whatever underlying storage it was given rather than its
own string storage, so sometimes it would hold a reference to a string
from the source file, and sometimes a string from the tokenized buffer's
string table. The diagnostics were always flushed before the source file
was destroyed, but not before the tokenized buffer was destroyed. So to
see the issue, you'd need to have a string literal with certain contents
followed by an identifier with a name that matched those contents.
The crash is made more reliable by holding references to the Semantics
IR's string map in its string table, rather than references to someone
else's strings. This also fixes a latent bug where passing a string
temporary to SemanticsIR::AddString would store a dangling reference in
the string table. Incidentally, AddString is also changed to perform
only one hash table lookup rather than two for each added string.
Jon Ross-Perkins
Jacob Schneider
Geoff Romer
Richard Smith