std/crypto: use finer-grained error sets in function signatures
Returning the `crypto.Error` error set for all crypto operations
was very convenient to ensure that errors were used consistently,
and to avoid having multiple error names for the same thing.
The flipside is that callers were forced to always handle all
possible errors, even those that could never be returned by a
function.
This PR makes all functions return union sets of the actual errors
they can return.
The error sets themselves are all limited to a single error.
Larger sets are useful for platform-specific APIs, but we don't have
any of these in `std/crypto`, and I couldn't find any meaningful way
to build larger sets.
This commit also reclaims +2 ZIR instruction tags by moving the
following to `extended`:
* func_var_args
* func_extra
* func_extra_var_args
The following ZIR instruction tag is added:
* func_inferred
These are currently incorrect according to the gitattributes(5) and
gitignore(5) man pages. However, it seems github ended up treating them
as we intended due to a bug until recently when that bug was fixed.
I've run into this footgun enough times, nearly every time I want
`ensureUnusedCapacity`, not `ensureCapacity`. This commit deprecates
`ensureCapacity` in favor of `ensureTotalCapacity` and introduces
`ensureUnusedCapacity`.
* AstGen: represent compile errors in ZIR rather than returning
`error.AnalysisFail`.
* ZIR: remove decl_ref and decl_val instructions. These are replaced by
`decl_ref_named` and `decl_val_named`, respectively, which will
probably get renamed in the future to the instructions that were just
deleted.
* AstGen: implement `@This()`, `@fence()`, `@returnAddress()`, and
`@src()`.
* AstGen: struct_decl improved to support fields_len=0 but have decls.
* AstGen: fix missing null bytes after compile error messages.
* SrcLoc: no longer depend on `Decl`. Instead have an explicit field
`parent_decl_node` which is an absolute AST Node index.
* Module: `failed_files` table can have null value, in which case the
key, which is a `*Scope.File`, will have ZIR errors in it.
* ZIR: implement text rendering of struct decls.
* CLI: introduce debug_usage and `zig astgen` command which is enabled
when the compiler is built in debug mode.
