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swift-mirror/validation-test/compiler_crashers_fixed
Hamish Knight c667d2b361 Use DefaultArgumentExpr for caller-side defaults
This commit changes how we represent caller-side
default arguments within the AST. Instead of
directly inserting them into the call-site, use
a DefaultArgumentExpr to refer to them indirectly.

The main goal of this change is to make it such
that the expression type-checker no longer cares
about the difference between caller-side and
callee-side default arguments. In particular, it
no longer cares about whether a caller-side
default argument is well-formed when type-checking
an apply. This is important because any
conversions introduced by the default argument
shouldn't affect the score of the resulting
solution.

Instead, caller-side defaults are now lazily
type-checked when we want to emit them in SILGen.
This is done through introducing a request, and
adjusting the logic in SILGen to be more lenient
with ErrorExprs. Caller-side defaults in primary
files are still also currently checked as a part
of the declaration by `checkDefaultArguments`.

Resolves SR-11085.
Resolves rdar://problem/56144412.
2019-11-20 15:07:32 -08:00
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