Since we have -Wswitch, this forces the developer to update all relevant
switches when an enum case is added.
Places where the default is just a FIXME are left alone.
This node type will be deleted (again) once the hlsl->vsir->tpf
translation is complete. It serves the purpose of allowing to keep
both real hlsl_ir_nodes and vsir_instructions in the hlsl_block,
until all the former can be translated into the latter.
We need users of a value to be freed before the value itself is.
Due to copy propagation or use of the pre-allocated error instruction,
static_initializers can contain values that will be used in function blocks.
Currently, if an expression successfully parses according to the bison grammar,
but for one reason or another cannot generate a meaningful IR instruction, we
abort parsing with YYABORT. This includes, for example, an undefined variable or
function, invalid swizzle or field reference, or a constructor with a complex or
non-numeric data type.
Aborting parsing is unfortunate, however, because it means that any further
errors in the program cannot be caught by the programmer, increasing the number
of times they will need to fix errors and recompile.
The idea of this patch is that any such expression will instead generate an IR
node whose data type is of HLSL_CLASS_ERROR. Any further expression which would
consume an "error" typed instruction will instead immediately return an
expression of type "error" (probably the same one) instead of aborting or doing
any other type-checking.
Currently these "error" instructions should not pass the parsing stage, since
hlsl_compile_shader() will immediately notice that compilation has failed and
skip any optimization, lowering, or bytecode-writing.
A further direction to take this is to pre-allocate one "error" expression
immediately when creating the HLSL parser, and return that expression when we
fail to allocate an hlsl_ir_node of any type. This means we do not need to
handle allocation errors when constructing nodes, saving us quite a lot of error
handling (which is not only tedious but currently often broken, if nothing else
by virtue of neglecting cleanup of local variables).
