clarify which names can not be quoted

[maeder]

http://www.haskell.org/ghc/docs/6.12.2/html/users_guide/template-haskell.html#id665813

I suppose a primed identifier like x' or T' can not be quoted, because they would be scanned as character.

Maybe all identifiers containing primes should be disallowed being quoted by one or two leading primes.

In any case, the documentation should match the implementation.

[simonpj]

Any chance you could send a documentation patch? Thanks!

Simon

[maeder]

Add: "Names containing primes can not be quoted if they would become legal haskell character literals."  http://www.haskell.org/onlinelibrary/syntax-iso.html#sect9.2 (char)

Any chance you disallow all names containing primes in the implementation just to increase the gap between a bad literal 'ab' and a difficult to read quote?

[maeder]

for a changed implementation add:

"Names containing primes can not be quoted in order to avoid confusion with character literals."

[maeder]

replace "primes" with "single-quotes"

[maeder]

http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/syntax-extns.html#syntax-stolen wrongly mentions -XPolyKinds in:

'varid
    Stolen by: -XTemplateHaskell and -XPolyKinds 

http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/template-haskell.html

'f has type Name, and names the function f. Similarly 'C has type Name and names the data constructor C. In general 'thing interprets thing in an expression context. 

should be extended: "Names f or C that form (or start with) a legal character if quoted, cannot be quoted."

Prelude> let a' = 1
Prelude> :t 'a'
'a' :: Char
Prelude> let ab' = 1
Prelude> :t 'ab'
'ab' :: Language.Haskell.TH.Syntax.Name
Prelude> let a'' = 1
Prelude> :t 'a''

<interactive>:1:5:
    lexical error in string/character literal at end of input
Prelude> let a'a' = 1
Prelude> :t 'a'a'

<interactive>:1:1:
    The function 'a' is applied to one argument,
    but its type `Char' has none
    In the expression: 'a' a'

[simonpj@…]

commit 0936621a72da0e8811d351be6f03edd5d724f711

Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri Mar 16 16:12:31 2012 +0000

    Fix documentation about TH and kind-promotion single-quote notation (Trac #4197)

 docs/users_guide/glasgow_exts.xml |   31 ++++++++++++++++++-------------
 1 files changed, 18 insertions(+), 13 deletions(-)

[simonpj]

Actually neither TH nor PolyKinds steal 'x or 'T:

• In a character literal 'x', the character literal wins both times.
• If you have just 'x all by itself, it's rejected unless you have PolyKinds or TemplateHaskell.

So the meaning never changes; nothing is stolen. So I will

• Remove the 'varid item from http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/syntax-extns.html#syntax-stolen algother.
• I'll add the clarification you suggest to the TH section.