#12178: Allow inline pragmas on pattern synonyms -------------------------------------+------------------------------------- Reporter: mpickering | Owner: (none) Type: feature request | Status: new Priority: high | Milestone: 8.8.1 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: | PatternSynonyms, newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
Why would a pattern synonym not get inlined by default, always?
The only disadvantage to inlining is code size; and that applies equally to all inlining decisions, whether for pattern synonyms or any other function. Consider {{{ pattern P a = [[[[a]]]] f x = P (x+1) g y = P (y-1) }}} Here's what it compiles to, without inlining {{{ $bP x = (:) ((:) ((:) ((:) x []) []) []) [] f x = $bP (x+1) g y = $bP (y-1) }}} Yes, we could inline `$bP`: {{{ f x = (:) ((:) ((:) ((:) (x+1) []) []) []) [] g y = (:) ((:) ((:) ((:) (y-1) []) []) []) [] }}} But really nothing much was gained by inlining the builder `$bp`. It's the same for matching. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12178#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler