Incorrect parsing of declarations

GHC's parser seems to accept incorrect Haskell programs, which leads to very confusing error messages. Here is an example:

f x = T
 
g 1 = 10
g x

data T = T

When trying to compile this GHC reports:

test.hs:1:6: Not in scope: data constructor `T'

This happened in much larger module, where I had forgotten to complete one of the equations for a function, but ended up looking for what is wrong with the (completely unrelated) "data" declaration.

This might be related to Template Haskell because a smaller example---a file containing only the literal 1---results in complaints about some template Haskell type not being in the Num class.

I am compiling the module without any pragmas or flags, so I would not think that TH is enabled.

Trac metadata

Trac field	Value
Version	6.12.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Parser)
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