Aggregate all requirement failures (regardless of kind) that belong
to the same locator and diagnose them as an ambiguity (if there is
more than one overload) or as the singular failure if all solutions
point to the same overload.
If we don't have an associated TypeRepr for a
contextual type in the constraint system, dump the
ASTNode that it's for instead.
Before:
```
Contextual Type: $T2
```
After:
```
Contextual Type: $T2 at DeclRef@/Users/hamish/src/swift-test-arena/swift-test-arena/main.swift:1493:21
```
In some situations `getContextualType` for a contextual type
locator is going to return then empty type. This happens because
e.g. optional-some patterns and patterns with incorrect type don't
have a contextual type for initialization expression but use
a conversion with contextual locator nevertheless to indicate
the purpose. This doesn't affect non-ambiguity diagnostics
because mismatches carry both `from` and `to` types.
Resolves: rdar://problem/103739206
rather than relying on PackElementExprs collected by preCheck.
This handles pack element expressions and pack element type reprs, and enforces that
all packs expanded by a given pack expansion expression all have the same shape.
Once the parser creates PackExpansionExpr directly (based on a dedicated syntax instead
of postfix '...'), the code in preCheck for identifying and creating pack expansions
can simply be deleted.
Rather than set closure discriminators in both the parser (for explicit
closures) and then later as part of contextualizing closures (for
autoclosures), do so via a request that sets all of the discriminators
for a given context.
`getValue` -> `value`
`getValueOr` -> `value_or`
`hasValue` -> `has_value`
`map` -> `transform`
The old API will be deprecated in the rebranch.
To avoid merge conflicts, use the new API already in the main branch.
rdar://102362022
Rather than lookup up the macro by name again during constraint
application, use the overload choice for the macro as recorded in the
constraint system to apply the correct macro.
Although the declaration of macros doesn't appear in Swift source code
that uses macros, they still operate as declarations within the
language. Rework `Macro` as `MacroDecl`, a generic value declaration,
which appropriate models its place in the language.
The vast majority of this change is in extending all of the various
switches on declaration kinds to account for macros.
Instead of checking for unavailability attributes directly in the solver, use `AvailableAttr::isUnavailable` which checks the enclosing extension too, if necessary.
Resolves rdar://92364955
Replace the use of bool and pointer returns for
`walkToXXXPre`/`walkToXXXPost`, and instead use
explicit actions such as `Action::Continue(E)`,
`Action::SkipChildren(E)`, and `Action::Stop()`.
There are also conditional variants, e.g
`Action::SkipChildrenIf`, `Action::VisitChildrenIf`,
and `Action::StopIf`.
There is still more work that can be done here, in
particular:
- SourceEntityWalker still needs to be migrated.
- Some uses of `return false` in pre-visitation
methods can likely now be replaced by
`Action::Stop`.
- We still use bool and pointer returns internally
within the ASTWalker traversal, which could likely
be improved.
But I'm leaving those as future work for now as
this patch is already large enough.
