Wrong diagnostics for ternary expression when only the colon is missing

[whiteio]

Description

When diagnostics are generated for ternary expressions where the : is missing but both of the first and second choice expressions are present, the incorrect diagnostic message is used and the wrong Fix-It is applied.

Steps to Reproduce

Example:

foo ? 1 2

This results in the following diagnostic message and Fix-It:

expected ':' and expression after '? ...' in ternary expression

foo ? 1 : <#expression#>2

As the expression isn't missing in the example I expected the following diagnostic message and Fix-It:

expected ':' after '? ...' in ternary expression

foo ? 1 : 2

[ahoppen]

Tracked in Apple’s issue tracker as rdar://108750446