These expressions are a little trickier than most because they include an implicit call to an allocator function. The database tells us which function to call, but we have to synthesize the allocation size and alignment arguments ourselves. The alignment argument, if it exists, is always a constant, but the size argument requires multiplication by the element count for most `NewArrayExpr`s. I introduced the new `TranslatedAllocationSize` class to handle this.
The IR avoids having non-trivially-copyable and non-trivially-assignable types in register results, because objects of those types need to exist at a particular memory location. The `InitializeParameter` and `Uninitialized` instructions were violating this restriction because they returned register results, which were then stored into the destination location via a `Store`.
This change makes those two instructions take the destination address as an operand, and return a memory result representing the (un-)initialized memory, removing the need for a separate `Store` instruction.
Casts to `void` did not have a semantic conversion type in the AST, so they also weren't getting generated correctly in the IR. I've added a `VoidConversion` class to the AST, along with tests. I've also added IR translation for such conversions, using a new `ConvertToVoid` opcode. I'm not sure if it's really necessary to generate an instruction to represent this, but it may be useful for detecting values that are explicitly unused (e.g. return value from a call).
I added two new sanity queries for the IR to detect the following:
- IR blocks with no successors, which usually indicates bad IR translation
- Phi instruction without an operand for one of the predecessor blocks.
These sanity queries found another subtle IR translation bug. If an expression that is normally translated as a condition (e.g. `&&`, `||`, or parens in certain contexts) has a constant value, we were not creating a `TranslatedExpr` for the expression at all. I changed it to always treat a constant condition as a non-condition expression.
