This allows us to eliminate some special casing around things like
parens, and allows the code to work for other code involving expressions
that are semantically neutral.
We now store an entire OverloadChoice in the unviable candidates
list (which is used for error recovery), just like we store them
for viable candidates.
The additional information isn't used, so NFC.
Consider different overload choices for the same location in evaluation
order, this makes overload resolution more predictable because it's going
to follow expression bottom-up, that prevents situations when some
expressions are considered ambigious because choices taken further up
equate the score, instead each level is given distinct weight
based on evaluation order.
Resolves: rdar://problem/31888810
Presence of some constraints (Subtype at least) requires a certain
contextual ranking of the type variables associated with them when
it comes to picking bindings, otherwise it might lead to no or
invalid solutions, because only a set of the bindings for the best
type variable is attempted.
Resolves: rdar://problem/22898292
Presence of some constraints (Subtype at least) requires a certain
contextual ranking of the type variables associated with them when
it comes to picking bindings, otherwise it might lead to no or
invalid solutions, because only a set of the bindings for the best
type variable is attempted.
Resolves: rdar://problem/22898292
For the moment, update the sole caller to not infer Any in cases where
neither argument was Any. This is in part because not all the cases are
handled here and the result of inferring Any will be to miss appropriate
bindings in certain cases. It is also in part because by inferring Any
we may end up deferring diagnostics until later in a function, which may
result in very hard to understand diagnostics for users.
This will be revisted once all the cases are properly handled here.
Currently edge related to the parameter bindings is contracted
without properly checking if newly created equivalence class has
the same inout & l-value requirements. This patch improves the
situation by disallowing contraction of the edges related to parameter
binding constraint where left-hand side has `inout` attribute set.
Such guarantees that parameter can get `inout` type assigned when
argument gets `l-value` type.
Resolves: rdar://problem/33429010
Change the potential binding ranking logic to prefer type variables
which don't have other type variables related to them, but have literal
bindings, over the ones that do have other type variables.
The naming here might not be perfect as it's not the only place that we
bind types to typevars in matchTypes, but it is a step towards cleaning
things up a bit. I'll revisit naming after I get a better idea what
other common code there may be that can get factored out.
When dealing with explicit coercions apply their conversions
early to avoid searching for solutions with incorrect types,
and therefore prune search space.
Move disjunction selection logic one level up from the `solveSimplified`
which allows to simplify its logic and avoid collecting disjunctions
multiple times for each solver step.
Sort constraint components/buckets based on how many disjunctions
they have, that helps to prune some of the branches with incorrect
solutions early which limits overall depth of the search.
Resolves: SR-4714
If we allow the right-hand type to be bound first, it can artificially
limit the options for the left-hand side, so attempt to delay binding of
the right-hand side types until after we've chosen something for the
left-hand side.
The test here will not fail without this change, but will fail without
this change if the ConstraintGraph.cpp changes from @xedin's edge
contraction patch (https://github.com/apple/swift/pull/11118) are
applied.
While shrinking we have to allocate containers for the reduced domains
for some of the candidates, it's currently done using permanent arena
of the `ASTContext` allocator. This patch changes candidate solver to
use arena associated with the parent constraint system, which significantly
limits lifetime of domain containers.
Currently we have a number of unsolved disjunctions hard-coded to 5,
which breaks some existing code by terminating shrinking too early.
This patch makes it a command-line option so users have control over
what that threshold can be.
Resolves: rdar://problem/33433595
The distinction was made between these two because of rdar://25341015,
wherein we needed a diagnostic that could detect the shadowing of
global functions by calls in protocols that don't match any
of the protocol's members.
This used to function by hoping that we had an argument tuple type lying
around after type checking. The expr cleaner would re-write that
type into the AST and we would look up based on it. Now that we write
Type() into the AST on failure, we must instead type check the
component parts of the argument themselves to form a tuple
type to make the lookup.
When we track which expressions we're already in the middle of type
checking, we need to ensure that we also track the constraint system
which has the types for that expression, and then transfer those types
into our current constraint system so that we do not fail to look them up.
Split out the code for selecting potential bindings into a separate file
as a first step before refactoring it for improved clarity and ease of
modification.
In some situations e.g. while trying to shrink domains of the type
variables before attempting search, use a flag to tell constraint
system to retain all of the viable solutions otherwise solver could
loose some of the information required to produce complete solution.
Resolves: rdar://problem/32726044
By default, end expression type checking after the elapsed process time
is more than 60 seconds for the current expression. This threshold can
be overridden by using -solver-expression-time-threshold=<seconds>.
Resolves rdar://problem/32859654
