Re: Stability of Uniques

Hmm. Thank you for pointing this out, it made me realize things are more subtle than I had thought. The uniques in the typechecked AST correspond to the 'abe_mono' field of ABExport (the monomorphic bindings within a binding group), while the uniques in the renamed AST correspond to the 'abe_poly' fields instead (you can see this in your example too). Edsko PS. Reading that "understanding the True Meaning of [ABExport] could get me a PhD" in the ghc comments was a little frightening :) On Wed, Mar 27, 2013 at 2:37 PM, Simon Peyton-Jones wrote:

Indeed the type checker does not actually clone identifiers. ****

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ghc -c -ddump-rn -ddump-tc -dppr-debug Foo.hs****

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==================== Renamer ====================****

nonrec {Foo.hs:3:1-8}****

main:Foo.f{v r0}****

main:Foo.*f{v r0}*****

= {Foo.hs:3:5-8}****

ghc-prim:GHC.Types.True{(w) d 6u}****

<>****

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TYPE SIGNATURES****

( main:Foo.f{v r0} [lid] :: ghc-prim:GHC.Types.Bool{(w) tc 3c} ) :: ghc-prim:GHC.Types.Bool{(w) tc 3c}****

TYPE CONSTRUCTORS****

COERCION AXIOMS****

Dependent modules: []****

Dependent packages: [base, ghc-prim, integer-gmp]****

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==================== Typechecker ====================****

{Foo.hs:3:1-8}****

AbsBinds****

[]****

[]****

[( main:Foo*.f{v r0}* [lid] :: ghc-prim:GHC.Types.Bool{(w) tc 3c} ) <= ( f{v a9H} [lid] :: ghc-prim:GHC.Types.Bool{(w) tc 3c} )****

<>]****

( main:Foo.f{v r0} [lid] :: ghc-prim:GHC.Types.Bool{(w) tc 3c} )****

:: ghc-prim:GHC.Types.Bool{(w) tc 3c}****

[LclId]****

{Foo.hs:3:1-8}****

( f{v a9H} [lid] :: ghc-prim:GHC.Types.Bool{(w) tc 3c} )****

:: ghc-prim:GHC.Types.Bool{(w) tc 3c}****

[LclId]****

( f{v a9H} [lid] :: ghc-prim:GHC.Types.Bool{(w) tc 3c} )****

= {Foo.hs:3:5-8}****

ghc-prim:GHC.Types.True{(w) v 6v}****

<>****

EvBinds{}****

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*From:* Edsko de Vries [mailto:edskodevries@gmail.com] *Sent:* 27 March 2013 14:04 *To:* Simon Peyton-Jones *Cc:* ghc-devs@haskell.org *Subject:* Re: Stability of Uniques****

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So is there any way that I can see that an identifier in the renamed AST is really the same as an identifier in the typechecked AST?****

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On Wed, Mar 27, 2013 at 1:57 PM, Simon Peyton-Jones wrote:****

Yes, locally-bound uniques change all the time, to maintain scoping hygiene. But top-level things from other modules have uniques that do not change.****

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simon****

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*From:* ghc-devs-bounces@haskell.org [mailto:ghc-devs-bounces@haskell.org] *On Behalf Of *Edsko de Vries *Sent:* 26 March 2013 15:05 *To:* ghc-devs@haskell.org *Subject:* Stability of Uniques****

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Hi all,****

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Consider the very simple test****

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module Test2 where****

f = True****

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When walking the AST after renaming I see that f has unique 1912603236 and True has unique 905969694. However, when walking the typechecked AST f seems to have unique 1627390565 instead. Should I expect that the unique associated with identifiers changes between renaming and typechecking? Or is there something else that I'm missing?

Thanks!

Edsko****

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