* `Value.toType` accepts a buffer parameter instead of an allocator
parameter and can no longer fail.
* Module: remove the unused `mod: *Module` parameter from various
functions.
* `Value.compare` now accepts a `Type` parameter which indicates the
type of both operands. There is also a `Value.compareHetero` which
accepts only Value parameters and supports comparing mixed types.
Likewise, `Value.eql` requires a `Type` parameter.
* `Value.hash` is removed; instead the hash map context structs now
have a `ty: Type` field, and the hash function lives there, where it
has access to a Value's Type when it computes a hash.
- This allowed the hash function to be greatly simplified and sound
in the sense that the same Values, even with different
representations, always hash to the same thing.
* Sema: Fix source location of zirCmp when an operand is runtime known
but needs to be comptime known.
* Remove unused target parameter from `Value.floatCast`.
AstGen is now completely independent from the rest of the compiler. It
ingests an AST tree and produces ZIR code as the output, without
depending on any of the glue code of the compiler.
The logic for putting ranges into the else prong is moved from AstGen to
Sema. However, logic to emit multi-items the same as single-items cannot
be done until TZIR supports mapping multiple items to the same block of
code. This will be simple to represent when we do the upcoming TZIR memory
layout changes.
Not yet implemented in this commit is the validation of duplicate
values. The trick is going to be emitting error messages with accurate
source locations, without adding extra source nodes to the ZIR
switch instruction.
This will be done by computing the respective AST node based on the
switch node (which we do have available), only when a compile error
occurs and we need to know the source location to attach the message to.
