cache-distribution.diff

diff --git a/src/core/CompUnit/Repository/FileSystem.pm6 b/src/core/CompUnit/Repository/FileSystem.pm6
index 5e17734af..ce7748463 100644
--- a/src/core/CompUnit/Repository/FileSystem.pm6
+++ b/src/core/CompUnit/Repository/FileSystem.pm6
@@ -3,6 +3,7 @@ class CompUnit::Repository::FileSystem does CompUnit::Repository::Locally does C
     has %!seen;   # cache distribution lookup for self!matching-dist(...)
     has $!precomp;
     has $!id;
+    has $!distribution;
     has $!precomp-stores;
     has $!precomp-store;
 
@@ -211,31 +212,42 @@ class CompUnit::Repository::FileSystem does CompUnit::Repository::Locally does C
 
     method !distribution {
         # Path contains a META6.json file, so only use paths/modules explicitly declared therein ( -I ./ )
-        my $dist = $!prefix.add('META6.json').f
-            ?? Distribution::Path.new($!prefix)
-            !! do {
-                # Path does not contain a META6.json file so grep for files to be used to map to arbitrary module names later ( -I ./lib )
-                # This is considered a developmental mode of library inclusion -- technically a Distribution, but probably a poorly formed one.
-                my &ls := { Rakudo::Internals.DIR-RECURSE($_).map({ .IO.relative(self!files-prefix).subst(:g, '\\', '/') }) };
-                Distribution::Hash.new(:prefix(self!files-prefix), %(
-                    name      => ~$!prefix, # must make up a name when using -Ilib / use lib 'lib'
-                    ver       => '*',
-                    api       => '*',
-                    auth      => '',
-                    files     => (my %files = %( # files is a non-spec internal field used by CompUnit::Repository::Installation included to make cross CUR install easier
-                        &ls(self!files-prefix.child('bin').absolute).map({ $_ => $_ }).Slip,
-                        &ls(self!files-prefix.child('resources').absolute).map({
-                            $_ ~~ m/^resources\/libraries\/(.*)/
-                                ?? ('resources/libraries/' ~ ($0.IO.dirname eq '.'??''!!$0.IO.dirname~"/") ~ $0.IO.basename.subst(/^lib/, '').subst(/\..*/, '') => $_)
-                                !! ($_ => $_)
-                        }).Slip,
-                    )),
-                    resources => %files.keys.grep(*.starts-with('resources/')).map(*.substr(10)).List, # already grepped resources/ for %files, so reuse that information
-                    provides  => &ls($!prefix.absolute).grep(*.ends-with(any(@extensions))).map({ $_.subst(:g, /\//, "::").subst(:g, /\:\:+/, '::').subst(/^.*?'::'/, '').subst(/\..*/, '') => $_ }).hash,
-                ));
-            };
-
-        return CompUnit::Repository::Distribution.new($dist);
+        $!distribution //= do {
+            my $dist = $!prefix.add('META6.json').f
+                ?? Distribution::Path.new($!prefix)
+                !! do {
+                    # Path does not contain a META6.json file so grep for files to be used to map to arbitrary module names later ( -I ./lib )
+                    # This is considered a developmental mode of library inclusion -- technically a Distribution, but probably a poorly formed one.
+                    my &ls := { Rakudo::Internals.DIR-RECURSE($_).map({ .IO.relative(self!files-prefix).subst(:g, '\\', '/') }) };
+                    Distribution::Hash.new(:prefix(self!files-prefix), %(
+                        name      => ~$!prefix, # must make up a name when using -Ilib / use lib 'lib'
+                        ver       => '*',
+                        api       => '*',
+                        auth      => '',
+                        files     => (my %files = %( # files is a non-spec internal field used by CompUnit::Repository::Installation included to make cross CUR install easier
+                            &ls(self!files-prefix.child('bin').absolute).map({ $_ => $_ }).Slip,
+                            &ls(self!files-prefix.child('resources').absolute).map({
+                                $_ ~~ m/^resources\/libraries\/(.*)/
+                                    ?? ('resources/libraries/' ~ ($0.IO.dirname eq '.'??''!!$0.IO.dirname~"/") ~ $0.IO.basename.subst(/^lib/, '').subst(/\..*/, '') => $_)
+                                    !! ($_ => $_)
+                            }).Slip,
+                        )),
+                        resources => %files.keys.grep(*.starts-with('resources/')).map(*.substr(10)).List, # already grepped resources/ for %files, so reuse that information
+                        provides  => &ls($!prefix.absolute)
+                            .grep(*.ends-with(any(@extensions)))
+                            .map({
+                                $_.subst(:g, /\//, "::")
+                                    .subst(:g, /\:\:+/, '::')
+                                    .subst(/^.*?'::'/, '')
+                                    .subst(/\..*/, '')
+                                 => $_
+                             })
+                            .hash,
+                    ));
+                };
+
+            CompUnit::Repository::Distribution.new($dist);
+        }
     }
 
     method resource($dist-id, $key) {