split from #24198
This is a required refactor for the only good solution I've been able to
think of for #4858 etc. Explanation:
---
`sigmatch` currently [disables
bindings](d6a71a1067/compiler/sigmatch.nim (L1956))
(except for binding to other generic parameters) when matching against
constraints of generic parameters. This is so when the constraint is a
general metatype like `seq`, the type matching will not treat all
following uses of `seq` as the type matched against that generic
parameter.
However to solve #4858 etc we need to bind `or` types with a conversion
match to the type they are supposed to be converted to (i.e. matching
`int literal(123)` against `int8 | int16` should bind `int8`[^1], not
`int`). The generic parameter constraint binding needs some way to keep
track of this so that matching `int literal(123)` against `T: int8 |
int16` also binds `T` to `int8`[^1].
The only good way to do this IMO is to generate a new "binding context"
when matching against constraints, then binding the generic param to
what the constraint was bound to in that context (in #24198 this is
restricted to just `or` types & concrete types with convertible matches,
it doesn't work in general).
---
`semtypinst` already does something similar for bindings of generic
invocations using `LayeredIdTable`, so `LayeredIdTable` is now split
into its own module and used in `sigmatch` for type bindings as well,
rather than a single-layer `TypeMapping`. Other modules which act on
`sigmatch`'s binding map are also updated to use this type instead.
The type is also made into an `object` type rather than a `ref object`
to reduce the pointer indirection when embedding it inside
`TCandidate`/`TReplTypeVars`, but only on arc/orc since there are some
weird aliasing bugs on refc/markAndSweep that cause a segfault when
setting a layer to its previous layer. If we want we can also just
remove the conditional compilation altogether and always use `ref
object` at the cost of some performance.
[^1]: `int8` binding here and not `int16` might seem weird, since they
match equally well. But we need to resolve the ambiguity here, in #24012
I tested disallowing ambiguities like this and it broke many packages
that tries to match int literals to things like `int16 | uint16` or
`int8 | int16`. Instead of making these packages stop working I think
it's better we resolve the ambiguity with a rule like "the earliest `or`
branch with the best match, matches". This is the rule used in #24198.
Move `symFromType` and `symNodeFromType` from `sem`, and `isSelf` and
`makeTypeDesc` from `concepts` into `semdata`.
`makeTypeDesc` was moved out from semdata [when the `concepts` module
was
added](6278b5d89a),
so its old position might have been intended. If not, `isSelf` can also
go in `ast`.
* Add testcase
This tries to use a concept with a doc comment which currently leads to a segfault
* Ignore nil nodes which happen when there are doc comments in new style concept
This was done instead of semming the comments since `semConceptDecl` says it only supports lists of actual statements
* Go with alternative fix: Sem comments but ignore them
Since `nil` could mean anything it is best to not silently ignore it (In case another nil problem happens in future
Also fix test case so it isn't an infinite loop
* refactoring in preparation for better, simpler name mangling that works with IC flawlessly
* use new disamb field
* see if this makes tests green
* make tests green again
* fixes#15210 [backport:1.2]
* make tests green
* make ordinal work
* makes Swapable test compile
* make Indexable example work
* concepts: 'self' is now 'Self'
* concepts: make Dictionary example compile
* document the new concept implementation
* concepts: make typeDesc work properly
* concepts: allow documentation comments (d'oh)
