Previously code completion for 'catch' pattern bound values didn't work
correctly because code completion type checker fails to type check the
value decl in the pattern.
That was because the body of the 'do' statement is not type checked, so
the thrown error is not determined, then falled backed to the default
'Never', which doesn't matches any patterns.
To resolve this, always type check the body when typechecking 'catch'
patterns. Also, pretends 'do {}' throws 'any Error' even without
any throwing expressions in the body.
rdar://126699879
Enabling typed throws has introduced some spurious warnings about error
values of `Never` type on top of the custom "unreachable" diagnostics
for catch clauses, so suppress the new warnings---they aren't helpful.
Unify the duplicate pattern var checking in
pattern resolution such that it is always called
no matter how we end up type-checking the pattern.
This avoids incorrectly allowing duplicate pattern
vars to compile for patterns as a part of
multi-statement closures.
The parser's own re-declaration checking for local declarations has
slightly different behavior than Sema's re-declaration check.
Whereas Sema rejects this:
class C {
let x = 123
func x() {}
}
The parser accepts this:
func f() {
let x = 123
func x() {}
}
With Sema's check now handling both cases, fudge the behavior to
match the parser in the local case.
