This commit is the result of auditing the following files:
* StringBuffer.swift
* StringCharacterView.swift
* StringCore.swift
* StringInterpolation.swift.gyb
* StringLegacy.swift
`FixedPoint.swift.gyb` generates a massive amount of assertions:
one for each `Int` type (such as `UInt8` and `Int64`) as a source,
to one of each `Int` type as a destination, for each of 27 bit
patterns. By my math that's 8 * 8 * 27 == 1728 assertions.
As a result, when one of those assertions fails, it's difficult to
tell what went wrong.
Split each assertion into its own test case. This makes the test
take a little longer to run, but it produces much more valuable
output when it fails.
Previously, type checking arguments worked fine if the entire arg was
UnresolvedType, but if the type just contained UnresolvedType, the
constraint system always failed via explicitly constraining to
unresolved.
Now in TypeCheckConstraints, if the solution allows for free variables
that are UnresolvedType, then also convert any incoming UnresolvedTypes
into variables. At worst, in the solution these just get converted back
into the same Unresolved that they started with.
This change allows for incorrect tuple/function type possibilities to
make it back out to CSDiag, where they can be more precisely diagnosed
with callee info. The rest of the changes are to correctly figure
out the failure info when evaluating more types of Types.
New diagnosis for a partial part of an arg type not confroming. Tests
added for that. Expected errors changed in several places where we
now get real types in the diagnosis instead of '(_)' unresolved.
Silence Swift 3 migration warnings:
- Replace `--` and `++` with `-= 1` and `+= 1`.
- Replace screaming snake case identifiers with `#file` and `#line`.
Correctly determine callee closeness for func/ops that include generics
as part of more complicated parameters, i.e. tuple or closure args
containing generics as elements or args/results. Still only handling
single archetypes.
Also added code to check generic substitutions already made in the callee
parameters, which further helps diagnosis.
