[mlir] Make single value `ValueRange`s memory safer (#121996)

A very common mistake users (and yours truly) make when using
`ValueRange`s is assigning a temporary `Value` to it. Example:
```cpp
ValueRange values = op.getOperand();
apiThatUsesValueRange(values);
```

The issue is caused by the implicit `const Value&` constructor: As per
C++ rules a const reference can be constructed from a temporary and the
address of it taken. After the statement, the temporary goes out of
scope and `stack-use-after-free` error occurs.

This PR fixes that issue by making `ValueRange` capable of owning a
single `Value` instance for that case specifically. While technically a
departure from the other owner types that are non-owning, I'd argue that
this behavior is more intuitive for the majority of users that usually
don't need to care about the lifetime of `Value` instances.

`TypeRange` has similarly been adopted to accept a single `Type`
instance to implement `getTypes`.

0 files changed, 0 insertions, 0 deletions