Add StringPrimL to template-haskell

[ekmett]

In designing a template haskell lexer, you cannot get the same performance as alex, due to the fact that you cannot encode a "string"# literal to house the lookup tables for the encoded lexer.

Proposal: add "string"# literals to template-haskell as StringPrimL (or another suitable constructor) to Lit.

Then the quasiquoter can emit a data type that contains Addr# references to the link-time-locatable "string"#s permitting constant folding and inlining away the particular link time choice of Addr#.

[simonpj]

Done. One patch for GHC:

Fri Jul 30 14:19:22 BST 2010  simonpj@microsoft.com
  * * Add StringPrimL as a constructor for Template Haskell (Trac #4168)
    
  There are already constructors for IntPrim, FloatPrim etc,
  so this makes it more uniform.
    
  There's a corresponding patch for the TH library

and one for the template-haskell library:

Fri Jul 30 14:15:50 BST 2010  simonpj@microsoft.com
  * Add a StringPrimL constructor to the Lit type (fix Trac #4168)
  
  There's a corresponding patch in the main compiler

It's all very simple and uniform, but I have not tested it thoroughly. Would you like to? Meanwhile I'll mark it as fixed.

Simon