Avoid fingerprinting the absolute path to the source file

This change aims to make source files relocatable w.r.t. to the interface files produced by the compiler.
This is so that we can download interface files produced by a cloud build system and then reuse them in a local ghcide session

catch another case of implicit includes

actually use the implicit quote includes

add another missing case

recomp020

test that .hi files are reused even if .hs files are moved to a new location

Added recomp021 to record behaviour with non implicit includes

add a note

additional pointer to the note

Mention  #16956 in Note

1 files changed, 8 insertions, 5 deletions

diff --git a/compiler/GHC/Driver/Pipeline.hs b/compiler/GHC/Driver/Pipeline.hs
index 54221c4847..307499887d 100644
--- a/compiler/GHC/Driver/Pipeline.hs
+++ b/compiler/GHC/Driver/Pipeline.hs
@@ -291,7 +291,7 @@ compileOne' m_tc_result mHscMessage
          = (Interpreter, dflags2 { backend = Interpreter })
          | otherwise
          = (backend dflags, dflags2)
-       dflags  = dflags3 { includePaths = addQuoteInclude old_paths [current_dir] }
+       dflags  = dflags3 { includePaths = addImplicitQuoteInclude old_paths [current_dir] }
        hsc_env = hsc_env0 {hsc_dflags = dflags}
 
        -- -fforce-recomp should also work with --make
@@ -1234,7 +1234,7 @@ runPhase (RealPhase (Hsc src_flavour)) input_fn
   -- the .hs files resides) to the include path, since this is
   -- what gcc does, and it's probably what you want.
         let current_dir = takeDirectory basename
-            new_includes = addQuoteInclude paths [current_dir]
+            new_includes = addImplicitQuoteInclude paths [current_dir]
             paths = includePaths dflags0
             dflags = dflags0 { includePaths = new_includes }
 
@@ -1525,7 +1525,8 @@ runPhase (RealPhase cc_phase) input_fn
         let include_paths_global = foldr (\ x xs -> ("-I" ++ x) : xs) []
               (includePathsGlobal cmdline_include_paths ++ pkg_include_dirs)
         let include_paths_quote = foldr (\ x xs -> ("-iquote" ++ x) : xs) []
-              (includePathsQuote cmdline_include_paths)
+              (includePathsQuote cmdline_include_paths ++
+               includePathsQuoteImplicit cmdline_include_paths)
         let include_paths = include_paths_quote ++ include_paths_global
 
         -- pass -D or -optP to preprocessor when compiling foreign C files
@@ -1670,7 +1671,8 @@ runPhase (RealPhase (As with_cpp)) input_fn
         let global_includes = [ GHC.SysTools.Option ("-I" ++ p)
                               | p <- includePathsGlobal cmdline_include_paths ]
         let local_includes = [ GHC.SysTools.Option ("-iquote" ++ p)
-                             | p <- includePathsQuote cmdline_include_paths ]
+                             | p <- includePathsQuote cmdline_include_paths ++
+                                includePathsQuoteImplicit cmdline_include_paths]
         let runAssembler inputFilename outputFilename
               = liftIO $
                   withAtomicRename outputFilename $ \temp_outputFilename ->
@@ -1938,7 +1940,8 @@ doCpp logger tmpfs dflags unit_env raw input_fn output_fn = do
     let include_paths_global = foldr (\ x xs -> ("-I" ++ x) : xs) []
           (includePathsGlobal cmdline_include_paths ++ pkg_include_dirs)
     let include_paths_quote = foldr (\ x xs -> ("-iquote" ++ x) : xs) []
-          (includePathsQuote cmdline_include_paths)
+          (includePathsQuote cmdline_include_paths ++
+           includePathsQuoteImplicit cmdline_include_paths)
     let include_paths = include_paths_quote ++ include_paths_global
 
     let verbFlags = getVerbFlags dflags