Add comments about ModGuts instance envts (and re-order fields)

diff --git a/compiler/main/HscTypes.lhs b/compiler/main/HscTypes.lhs
index c1882d6..acb47c5 100644 (file)
--- a/compiler/main/HscTypes.lhs
+++ b/compiler/main/HscTypes.lhs
@@ -522,16 +522,9 @@ data ModGuts
        mg_usages    :: ![Usage],        -- Version info for what it needed
 
         mg_rdr_env   :: !GlobalRdrEnv,  -- Top-level lexical environment
        mg_usages    :: ![Usage],        -- Version info for what it needed
 
         mg_rdr_env   :: !GlobalRdrEnv,  -- Top-level lexical environment

-       mg_fix_env   :: !FixityEnv,      -- Fixity env, for things declared in
-                                        --   this module 
-
-       mg_inst_env     :: InstEnv,      -- Class instance enviroment fro
-                                        -- *home-package* modules (including
-                                        -- this one); c.f. tcg_inst_env
-       mg_fam_inst_env :: FamInstEnv,   -- Type-family instance enviroment
-                                        -- for *home-package* modules (including
-                                        -- this one); c.f. tcg_fam_inst_env

 
 

+       -- These fields all describe the things **declared in this module**
+       mg_fix_env   :: !FixityEnv,      -- Fixities

        mg_types     :: !TypeEnv,
        mg_insts     :: ![Instance],     -- Instances 
        mg_fam_insts :: ![FamInst],      -- Instances 
        mg_types     :: !TypeEnv,
        mg_insts     :: ![Instance],     -- Instances 
        mg_fam_insts :: ![FamInst],      -- Instances 

@@ -541,7 +534,19 @@ data ModGuts
        mg_deprecs   :: !Deprecations,   -- Deprecations declared in the module
        mg_hpc_info  :: !HpcInfo,        -- info about coverage tick boxes
         mg_modBreaks :: !ModBreaks,
        mg_deprecs   :: !Deprecations,   -- Deprecations declared in the module
        mg_hpc_info  :: !HpcInfo,        -- info about coverage tick boxes
         mg_modBreaks :: !ModBreaks,

-        mg_vect_info :: !VectInfo        -- Pool of vectorised declarations
+        mg_vect_info :: !VectInfo,        -- Pool of vectorised declarations
+
+       -- The next two fields are unusual, because they give instance
+       -- environments for *all* modules in the home package, including
+       -- this module, rather than for *just* this module.  
+       -- Reason: when looking up an instance we don't want to have to
+       --        look at each module in the home package in turn
+       mg_inst_env     :: InstEnv,      -- Class instance enviroment fro
+                                        -- *home-package* modules (including
+                                        -- this one); c.f. tcg_inst_env
+       mg_fam_inst_env :: FamInstEnv    -- Type-family instance enviroment
+                                        -- for *home-package* modules (including
+                                        -- this one); c.f. tcg_fam_inst_env

     }
 
 -- The ModGuts takes on several slightly different forms:
     }
 
 -- The ModGuts takes on several slightly different forms: