Introduce a fix/diagnostic when there is a contextual mismatch
between source and destination types of the assignment e.g.:
```swift
var x: Int = 0
x = 4.0 // destination expects an `Int`, but source is a `Double`
```
Some spots of constraint simplification logic are too eager to
fail right away without giving repair logic to run in diagnostic
mode and attempt to fix the problem. Failing early in diagnostic
mode means solver wouldn't be able to reach some possible
solutions which leads to subpar diagnostics.
This only comes into play when all other choices are coming from
constrained extensions, because there is no way to determine upfront
whether any are going to match it's better to be safe and add
key path dynamic member choice to the set too.
Resolves: [SR-11465](https://bugs.swift.org/browse/SR-11465)
Resolves: rdar://problem/55314724
When diagnosing failures in a function builder closure, we were
unnecessarily replacing the closure expression with its body,
destroying the AST and resulting in assertions due to DeclContext
mismatches. Fixes SR-11350 / rdar://problem/54590425.
Now that we associate argument labels for key path
subscript components, remove the special logic for
it. In addition, we can now search for callees
directly by using `getCalleeLocator`, as it should
now be able to find all the correct callees that
`getCalleeDeclAndArgs` does.
By using `getCalleeLocator`, we now also correctly
resolve callees for operator calls, meaning that
we can now use them with function builders. In
addition, we no longer incorrectly resolve callees
for calls made on SubscriptExprs.
Resolves SR-11439 & SR-11440.
Have FailureDiagnostic::getChoiceFor take a ConstraintLocator argument
which is passed through to getAnchormostCalleeLocator, and rename to
getAnchormostChoiceFor to make the semantics clear. In addition, add
a convenience getAnchormostChoice member for the common case of getting
the choice for the anchor of the failure's locator.
This change means we can now resolve callees for failures associated
with key path subscript components.
Resolves SR-11435.
Given we can now find overloads for applies of optional functions,
adjust the logic so we look at the call's direct callee. In addition,
tweak the logic so we don't assert on a ForceTryExpr.
mismatches in function types.
This improves the diagnostic in cases where we have argument-to-parameter
conversion failures or contextual type mismatches due to inout attribute
mismatches.
This helps us to filter out cases like operator overloads where
`Self` type comes from e.g. default for collection element -
`[1, "hello"].map { $0 + 1 }`. Main problem here is that
collection type couldn't be determined without unification to
`Any` and `+` failing for all numeric overloads is just a consequence.
This reinstates the use of direct adjacency information when gathering
constraints, effectively reverting
54bdd7b840.
Fixes the regression that commit caused, which is tracked by
rdar://problem/54274245.
