Precedence and associativity rules ignored when mixing infix type and data constructors in a single expression

[pat@…]

The following code:

infixr 5 `Foo`
infixr 6 `Bar`

data a `Foo` b = a `FOO` a `Bar` b
data a `Bar` b = a `BAR` b

fails to compile, ignoring the fixity declarations. It should be parsed as a FOO (a Bar b) but currently the parentheses are required, which misses the point of fixity annotations.

[simonpj]

See also #1702 (fix both at the same time).