The derived instance for Read of records wasn't quite right.
Consider
	data T = T1 T | T2 { x::Int }

The string "T1 T2 { x=2 }" should parse correctly as 
	T1 (T2 {x=2})
because of Haskell's odd precedence rules (record construction binds
even more tightly than application), but the derived Read didn't take
account of that.

drvrun020 is the regression test