diff --git a/Makefile b/Makefile
index 162d86fe3..b2e8268a2 100644
--- a/Makefile
+++ b/Makefile
@@ -381,7 +381,7 @@ ghcid-shake: $(call def-help,ghcid-shake, start ghcid autobuilder on Shake.hs)
 # run default GHCI
 STACKGHCI=$(STACK)
 # run latest GHCI for modern features
-#STACKGHCI=stack --stack-yaml=stack8.10.yaml
+#STACKGHCI=stack --stack-yaml=stack9.2.yaml
 
 # multi-package GHCI prompts
 ghci: $(call def-help,ghci, start ghci REPL on hledger-lib + hledger)
diff --git a/hledger-lib/Hledger/Data/Balancing.hs b/hledger-lib/Hledger/Data/Balancing.hs
index cf4b21a0f..a8582a561 100644
--- a/hledger-lib/Hledger/Data/Balancing.hs
+++ b/hledger-lib/Hledger/Data/Balancing.hs
@@ -903,8 +903,8 @@ tests_Balancing =
               transaction (fromGregorian 2019 01 01) [ vpost' "a" missingamt (balassert (num 1)) ]
             ]}
       assertRight ej
-      let Right j = ej
-      (jtxns j & head & tpostings & head & pamount & amountsRaw) @?= [num 1]
+      case ej of Right j -> (jtxns j & head & tpostings & head & pamount & amountsRaw) @?= [num 1]
+                 Left _  -> error' "balance-assignment test: shouldn't happen"
 
     ,testCase "same-day-1" $ do
       assertRight $ journalBalanceTransactions defbalancingopts $
diff --git a/hledger-lib/Hledger/Data/TransactionModifier.hs b/hledger-lib/Hledger/Data/TransactionModifier.hs
index b6dbe1ec6..3752bc36f 100644
--- a/hledger-lib/Hledger/Data/TransactionModifier.hs
+++ b/hledger-lib/Hledger/Data/TransactionModifier.hs
@@ -83,7 +83,7 @@ transactionModifierToFunction styles refdate TransactionModifier{tmquerytxt, tmp
   q <- simplifyQuery . fst <$> parseQuery refdate tmquerytxt
   let
     fs = map (tmPostingRuleToFunction styles q tmquerytxt) tmpostingrules
-    generatePostings ps = concatMap (\p -> p : map ($p) (if q `matchesPosting` p then fs else [])) ps
+    generatePostings = concatMap (\p -> p : map ($ p) (if q `matchesPosting` p then fs else []))
   Right $ \t@(tpostings -> ps) -> txnTieKnot t{tpostings=generatePostings ps}
 
 -- | Converts a 'TransactionModifier''s posting rule to a 'Posting'-generating function,
diff --git a/hledger-lib/Hledger/Data/Types.hs b/hledger-lib/Hledger/Data/Types.hs
index a8a6e8528..cce06d6f0 100644
--- a/hledger-lib/Hledger/Data/Types.hs
+++ b/hledger-lib/Hledger/Data/Types.hs
@@ -17,13 +17,19 @@ For more detailed documentation on each type, see the corresponding modules.
 -}
 
 -- {-# LANGUAGE DeriveAnyClass #-}  -- https://hackage.haskell.org/package/deepseq-1.4.4.0/docs/Control-DeepSeq.html#v:rnf
+{-# LANGUAGE CPP        #-}
 {-# LANGUAGE DeriveGeneric        #-}
 {-# LANGUAGE FlexibleInstances    #-}
 {-# LANGUAGE OverloadedStrings    #-}
 {-# LANGUAGE RecordWildCards      #-}
 {-# LANGUAGE StandaloneDeriving   #-}
 
-module Hledger.Data.Types
+module Hledger.Data.Types (
+  module Hledger.Data.Types,
+#if MIN_VERSION_time(1,11,0)
+  Year
+#endif
+)
 where
 
 import GHC.Generics (Generic)
@@ -47,6 +53,19 @@ import Text.Megaparsec (SourcePos)
 
 import Hledger.Utils.Regex
 
+-- synonyms for various date-related scalars
+#if MIN_VERSION_time(1,11,0)
+import Data.Time.Calendar (Year)
+#else
+type Year = Integer
+#endif
+type Month = Int     -- 1-12
+type Quarter = Int   -- 1-4
+type YearWeek = Int  -- 1-52
+type MonthWeek = Int -- 1-5
+type YearDay = Int   -- 1-366
+type MonthDay = Int  -- 1-31
+type WeekDay = Int   -- 1-7
 
 -- | A possibly incomplete year-month-day date provided by the user, to be
 -- interpreted as either a date or a date span depending on context. Missing
@@ -77,16 +96,6 @@ data DateSpan = DateSpan (Maybe Day) (Maybe Day) deriving (Eq,Ord,Generic)
 
 instance Default DateSpan where def = DateSpan Nothing Nothing
 
--- synonyms for various date-related scalars
-type Year = Integer
-type Month = Int     -- 1-12
-type Quarter = Int   -- 1-4
-type YearWeek = Int  -- 1-52
-type MonthWeek = Int -- 1-5
-type YearDay = Int   -- 1-366
-type MonthDay = Int  -- 1-31
-type WeekDay = Int   -- 1-7
-
 -- Typical report periods (spans of time), both finite and open-ended.
 -- A higher-level abstraction than DateSpan.
 data Period =
diff --git a/hledger-lib/Hledger/Utils/Regex.hs b/hledger-lib/Hledger/Utils/Regex.hs
index 704cf9895..e7c58e7dc 100644
--- a/hledger-lib/Hledger/Utils/Regex.hs
+++ b/hledger-lib/Hledger/Utils/Regex.hs
@@ -192,23 +192,25 @@ regexReplaceUnmemo re repl s = foldM (replaceMatch repl) s (reverse $ match (reC
     -- appropriate for this match. Or return an error message.
     replaceMatch :: Replacement -> String -> MatchText String -> Either RegexError String
     replaceMatch replpat s matchgroups =
-      erepl >>= \repl -> Right $ pre ++ repl ++ post
-      where
-        ((_,(off,len)):_) = elems matchgroups  -- groups should have 0-based indexes, and there should always be at least one, since this is a match
-        (pre, post') = splitAt off s
-        post = drop len post'
-        -- The replacement text: the replacement pattern with all
-        -- numeric backreferences replaced by the appropriate groups
-        -- from this match. Or an error message.
-        erepl = regexReplaceAllByM backrefRegex (lookupMatchGroup matchgroups) replpat
+      case elems matchgroups of 
+        [] -> Right s
+        ((_,(off,len)):_) ->   -- groups should have 0-based indexes, and there should always be at least one, since this is a match
+          erepl >>= \repl -> Right $ pre ++ repl ++ post
           where
-            -- Given some match groups and a numeric backreference,
-            -- return the referenced group text, or an error message.
-            lookupMatchGroup :: MatchText String -> String -> Either RegexError String
-            lookupMatchGroup grps ('\\':s@(_:_)) | all isDigit s =
-              case read s of n | n `elem` indices grps -> Right $ fst (grps ! n)  -- PARTIAL: should not fail, all digits
-                             _                         -> Left $ "no match group exists for backreference \"\\"++s++"\""
-            lookupMatchGroup _ s = Left $ "lookupMatchGroup called on non-numeric-backreference \""++s++"\", shouldn't happen"
+            (pre, post') = splitAt off s
+            post = drop len post'
+            -- The replacement text: the replacement pattern with all
+            -- numeric backreferences replaced by the appropriate groups
+            -- from this match. Or an error message.
+            erepl = regexReplaceAllByM backrefRegex (lookupMatchGroup matchgroups) replpat
+              where
+                -- Given some match groups and a numeric backreference,
+                -- return the referenced group text, or an error message.
+                lookupMatchGroup :: MatchText String -> String -> Either RegexError String
+                lookupMatchGroup grps ('\\':s@(_:_)) | all isDigit s =
+                  case read s of n | n `elem` indices grps -> Right $ fst (grps ! n)  -- PARTIAL: should not fail, all digits
+                                 _                         -> Left $ "no match group exists for backreference \"\\"++s++"\""
+                lookupMatchGroup _ s = Left $ "lookupMatchGroup called on non-numeric-backreference \""++s++"\", shouldn't happen"
     backrefRegex = toRegex' "\\\\[0-9]+"  -- PARTIAL: should not fail
 
 -- regexReplace' :: Regexp -> Replacement -> String -> String
diff --git a/hledger-lib/hledger-lib.cabal b/hledger-lib/hledger-lib.cabal
index 4c7101d6e..2c5d543cf 100644
--- a/hledger-lib/hledger-lib.cabal
+++ b/hledger-lib/hledger-lib.cabal
@@ -91,7 +91,7 @@ library
       Paths_hledger_lib
   hs-source-dirs:
       ./
-  ghc-options: -Wall -fno-warn-unused-do-bind -fno-warn-name-shadowing -fno-warn-missing-signatures -fno-warn-type-defaults -fno-warn-orphans
+  ghc-options: -Wall -fno-warn-unused-do-bind -fno-warn-name-shadowing -fno-warn-missing-signatures -fno-warn-type-defaults -fno-warn-orphans -fno-warn-incomplete-uni-patterns
   build-depends:
       Decimal >=0.5.1
     , Glob >=0.9
@@ -99,7 +99,7 @@ library
     , aeson-pretty
     , ansi-terminal >=0.9
     , array
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , blaze-markup >=0.5.1
     , bytestring
     , call-stack
@@ -141,7 +141,7 @@ test-suite doctest
   hs-source-dirs:
       ./
       test
-  ghc-options: -Wall -fno-warn-unused-do-bind -fno-warn-name-shadowing -fno-warn-missing-signatures -fno-warn-type-defaults -fno-warn-orphans
+  ghc-options: -Wall -fno-warn-unused-do-bind -fno-warn-name-shadowing -fno-warn-missing-signatures -fno-warn-type-defaults -fno-warn-orphans -fno-warn-incomplete-uni-patterns
   build-depends:
       Decimal >=0.5.1
     , Glob >=0.7
@@ -149,7 +149,7 @@ test-suite doctest
     , aeson-pretty
     , ansi-terminal >=0.9
     , array
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , blaze-markup >=0.5.1
     , bytestring
     , call-stack
@@ -194,7 +194,7 @@ test-suite unittest
   hs-source-dirs:
       ./
       test
-  ghc-options: -Wall -fno-warn-unused-do-bind -fno-warn-name-shadowing -fno-warn-missing-signatures -fno-warn-type-defaults -fno-warn-orphans
+  ghc-options: -Wall -fno-warn-unused-do-bind -fno-warn-name-shadowing -fno-warn-missing-signatures -fno-warn-type-defaults -fno-warn-orphans -fno-warn-incomplete-uni-patterns
   build-depends:
       Decimal >=0.5.1
     , Glob >=0.9
@@ -202,7 +202,7 @@ test-suite unittest
     , aeson-pretty
     , ansi-terminal >=0.9
     , array
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , blaze-markup >=0.5.1
     , bytestring
     , call-stack
diff --git a/hledger-lib/package.yaml b/hledger-lib/package.yaml
index 7ab78aa2f..eb57c2d06 100644
--- a/hledger-lib/package.yaml
+++ b/hledger-lib/package.yaml
@@ -32,7 +32,7 @@ extra-source-files:
 #data-files:
 
 dependencies:
-- base >=4.11 && <4.16
+- base >=4.11 && <4.17
 - aeson >=1
 - aeson-pretty
 - ansi-terminal >=0.9
@@ -84,6 +84,8 @@ ghc-options:
 - -fno-warn-missing-signatures
 - -fno-warn-type-defaults
 - -fno-warn-orphans
+# XXX seems new in 9.2, fix these
+- -fno-warn-incomplete-uni-patterns
 
 source-dirs: 
 #- other/ledger-parse
diff --git a/hledger-ui/hledger-ui.cabal b/hledger-ui/hledger-ui.cabal
index b364fdbdb..d8071f29b 100644
--- a/hledger-ui/hledger-ui.cabal
+++ b/hledger-ui/hledger-ui.cabal
@@ -67,7 +67,7 @@ executable hledger-ui
   build-depends:
       ansi-terminal >=0.9
     , async
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , brick >=0.23
     , cmdargs >=0.8
     , containers >=0.5.9
diff --git a/hledger-ui/package.yaml b/hledger-ui/package.yaml
index a03ec62e8..279e8ad6a 100644
--- a/hledger-ui/package.yaml
+++ b/hledger-ui/package.yaml
@@ -45,7 +45,7 @@ dependencies:
 - hledger >=1.24.99 && <1.25
 - ansi-terminal >=0.9
 - async
-- base >=4.11 && <4.16
+- base >=4.11 && <4.17
 - cmdargs >=0.8
 - containers >=0.5.9
 - data-default
diff --git a/hledger-web/hledger-web.cabal b/hledger-web/hledger-web.cabal
index 6e3041c53..e0b79b361 100644
--- a/hledger-web/hledger-web.cabal
+++ b/hledger-web/hledger-web.cabal
@@ -155,7 +155,7 @@ library
   build-depends:
       Decimal >=0.5.1
     , aeson >=1
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , base64
     , blaze-html
     , blaze-markup
diff --git a/hledger-web/package.yaml b/hledger-web/package.yaml
index ea542dc86..362139c51 100644
--- a/hledger-web/package.yaml
+++ b/hledger-web/package.yaml
@@ -102,7 +102,7 @@ library:
   - hledger-lib >=1.24.99 && <1.25
   - hledger >=1.24.99 && <1.25
   - aeson >=1
-  - base >=4.11 && <4.16
+  - base >=4.11 && <4.17
   - base64
   - blaze-html
   - blaze-markup
diff --git a/hledger/hledger.cabal b/hledger/hledger.cabal
index 264101226..4a491ba82 100644
--- a/hledger/hledger.cabal
+++ b/hledger/hledger.cabal
@@ -142,7 +142,7 @@ library
     , Diff
     , aeson >=1
     , ansi-terminal >=0.9
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , bytestring
     , cmdargs >=0.10
     , containers >=0.5.9
@@ -192,7 +192,7 @@ executable hledger
       Decimal >=0.5.1
     , aeson >=1
     , ansi-terminal >=0.9
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , bytestring
     , cmdargs >=0.10
     , containers >=0.5.9
@@ -242,7 +242,7 @@ test-suite unittest
       Decimal >=0.5.1
     , aeson >=1
     , ansi-terminal >=0.9
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , bytestring
     , cmdargs >=0.10
     , containers >=0.5.9
@@ -289,7 +289,7 @@ benchmark bench
       Decimal >=0.5.1
     , aeson >=1
     , ansi-terminal >=0.9
-    , base >=4.11 && <4.16
+    , base >=4.11 && <4.17
     , bytestring
     , cmdargs >=0.10
     , containers >=0.5.9
diff --git a/hledger/package.yaml b/hledger/package.yaml
index 482e250bd..07741d7f8 100644
--- a/hledger/package.yaml
+++ b/hledger/package.yaml
@@ -99,7 +99,7 @@ dependencies:
 - hledger-lib >=1.24.99 && <1.25
 - aeson >=1
 - ansi-terminal >=0.9
-- base >=4.11 && <4.16
+- base >=4.11 && <4.17
 - bytestring
 - cmdargs >=0.10
 - containers >=0.5.9
diff --git a/stack9.2.yaml b/stack9.2.yaml
new file mode 100644
index 000000000..42477e7fe
--- /dev/null
+++ b/stack9.2.yaml
@@ -0,0 +1,272 @@
+# stack build plan using GHC 9.2.1
+# XXX This is WIP; some deps like shakespeare don't build yet. hledger-lib builds.
+
+nix:
+  pure: false
+  packages: [perl gmp ncurses zlib]
+
+resolver: ghc-9.2.1
+
+packages:
+- hledger-lib
+- hledger
+- hledger-ui
+- hledger-web
+
+# for https://github.com/yesodweb/shakespeare/issues/261, eg
+allow-newer: true
+
+extra-deps:
+# for hledger-lib:
+- Decimal-0.5.2
+- Glob-0.10.2
+- OneTuple-0.3.1
+- Only-0.1
+- StateVar-1.2.2
+- aeson-2.0.2.0
+- aeson-pretty-0.8.9
+- ansi-terminal-0.11.1
+- ansi-wl-pprint-0.6.9
+- assoc-1.0.2
+- attoparsec-0.14.2
+- base-compat-0.12.1
+- base-compat-batteries-0.12.1
+- base-orphans-0.8.6
+- bifunctors-5.5.11
+- blaze-builder-0.4.2.2
+- blaze-markup-0.8.2.8
+- cabal-doctest-1.0.9
+- call-stack-0.4.0
+- case-insensitive-1.2.1.0
+- cassava-0.5.2.0
+- cassava-megaparsec-2.0.4
+- clock-0.8.2
+- cmdargs-0.10.21
+- colour-2.3.6
+- comonad-5.0.8
+- contravariant-1.5.5
+- csv-0.1.2
+- data-default-0.7.1.1
+- data-default-class-0.1.2.0
+- data-default-instances-containers-0.0.1
+- data-default-instances-dlist-0.0.1
+- data-default-instances-old-locale-0.0.1
+- data-fix-0.3.2
+- distributive-0.6.2.1
+- dlist-1.0
+- doclayout-0.3.1.1
+- emojis-0.1.2
+- extra-1.7.10
+- file-embed-0.0.15.0
+- hashable-1.4.0.1
+- hashtables-1.3
+- html-1.0.1.2
+- indexed-traversable-0.1.2
+- indexed-traversable-instances-0.1.1
+- integer-logarithms-1.0.3.1
+- megaparsec-9.2.0
+- microlens-0.4.12.0
+- microlens-th-0.4.3.10
+- old-locale-1.0.0.7
+- optparse-applicative-0.16.1.0
+- parser-combinators-1.3.0
+- pretty-simple-4.0.0.0
+- prettyprinter-1.7.1
+- prettyprinter-ansi-terminal-1.1.3
+- primitive-0.7.3.0
+- random-1.2.1
+- regex-base-0.94.0.2
+- regex-tdfa-1.3.1.1
+- safe-0.3.19
+- scientific-0.3.7.0
+- semialign-1.2.0.1
+- semigroupoids-5.3.6
+- splitmix-0.1.0.4
+- strict-0.4.0.1
+- tabular-0.2.2.8
+- tagged-0.8.6.1
+- tasty-1.4.2.1
+- tasty-hunit-0.10.0.3
+- text-short-0.1.4
+- th-abstraction-0.4.3.0
+- these-1.1.1.1
+- time-compat-1.9.6.1
+- timeit-2.0
+- transformers-compat-0.6.1.6
+- uglymemo-0.1.0.1
+- unbounded-delays-0.1.1.1
+- unordered-containers-0.2.16.0
+- utf8-string-1.0.2
+- uuid-types-1.0.5
+- vector-0.12.3.1
+- wcwidth-0.0.2
+- witherable-0.4.2
+# for hledger:
+- Diff-0.4.0
+- blaze-html-0.9.1.2
+- control-monad-free-0.6.2
+- githash-0.1.6.2
+- lucid-2.11.0
+- math-functions-0.3.4.2
+- mmorph-1.2.0
+- shakespeare-2.0.25
+- split-0.2.3.4
+- temporary-1.3
+- th-compat-0.1.3
+- th-lift-0.8.2
+- utility-ht-0.0.16
+- wizards-1.0.3
+# for hledger-ui:
+- QuickCheck-2.14.2
+- async-2.2.4
+- brick-0.65
+- cereal-0.5.8.2
+- config-ini-0.2.4.0
+- data-clist-0.1.2.3
+- fsnotify-0.3.0.1
+- hfsevents-0.1.6
+- microlens-ghc-0.4.13.1
+- microlens-mtl-0.2.0.1
+- microlens-platform-0.4.2.1
+- parallel-3.2.2.0
+- text-zipper-0.11
+- unix-compat-0.5.3
+- vty-5.33
+- word-wrap-0.5
+# for hledger-web:
+- HUnit-1.6.2.0
+- alex-3.2.6
+- appar-0.1.8
+- asn1-encoding-0.9.6
+- asn1-parse-0.9.5
+- asn1-types-0.3.4
+- attoparsec-iso8601-1.0.2.0
+- auto-update-0.1.6
+- base-unicode-symbols-0.2.4.2
+- base64-0.4.2.3
+- base64-bytestring-1.2.1.0
+- basement-0.0.12
+- bsb-http-chunked-0.0.0.4
+- byteable-0.1.1
+- byteorder-1.0.4
+- cipher-aes-0.2.11
+- clientsession-0.9.1.2
+- conduit-1.3.4.2
+- conduit-extra-1.3.5
+- connection-0.3.1
+- cookie-0.4.5
+- cprng-aes-0.6.1
+- crypto-api-0.13.3
+- crypto-cipher-types-0.0.9
+- crypto-random-0.0.9
+- cryptonite-0.29
+- cryptonite-conduit-0.2.2
+- css-text-0.1.3.0
+- easy-file-0.2.2
+- email-validate-2.3.2.15
+- entropy-0.4.1.7
+- fast-logger-3.0.5
+- ghc-byteorder-4.11.0.0.10
+- happy-1.20.0
+- haskell-lexer-1.1
+- hjsmin-0.2.0.4
+- hourglass-0.2.12
+- hspec-2.9.3
+- hspec-core-2.9.3
+- hspec-discover-2.9.3
+- hspec-expectations-0.8.2
+- html-conduit-1.3.2.2
+- http-api-data-0.4.3
+- http-client-0.7.9
+- http-client-tls-0.3.5.3
+- http-conduit-2.3.8
+- http-date-0.0.11
+- http-types-0.12.3
+- http2-3.0.2
+- iproute-1.7.12
+- language-javascript-0.7.1.0
+- libyaml-0.1.2
+- lift-type-0.1.0.1
+- lifted-base-0.2.3.12
+- memory-0.16.0
+- mime-types-0.1.0.9
+- monad-control-1.0.3.1
+- monad-logger-0.3.36
+- monad-loops-0.4.3
+- mono-traversable-1.0.15.3
+- network-3.1.2.5
+- network-byte-order-0.1.6
+- network-uri-2.6.4.1
+- old-time-1.1.0.3
+- path-pieces-0.2.1
+- pem-0.2.4
+- persistent-2.13.2.1
+- persistent-template-2.12.0.0
+- pretty-show-1.10
+- psqueues-0.2.7.3
+- quickcheck-io-0.2.0
+- resource-pool-0.2.3.2
+- resourcet-1.2.4.3
+- securemem-0.1.10
+- setenv-0.1.1.3
+- silently-1.2.5.2
+- simple-sendfile-0.2.30
+- skein-1.0.9.4
+- socks-0.6.1
+- stm-chans-3.0.0.6
+- streaming-commons-0.2.2.3
+- tagsoup-0.14.8
+- tf-random-0.5
+- th-lift-instances-0.1.18
+- time-manager-0.0.0
+- tls-1.5.5
+- transformers-base-0.4.6
+- typed-process-0.2.8.0
+- unix-time-0.4.7
+- unliftio-0.2.20
+- unliftio-core-0.2.0.1
+- vault-0.3.1.5
+- vector-algorithms-0.8.0.4
+- wai-3.2.3
+- wai-app-static-3.1.7.2
+- wai-cors-0.2.7
+- wai-extra-3.1.7
+- wai-handler-launch-3.0.3.1
+- wai-logger-2.3.6
+- warp-3.3.18
+- word8-0.1.3
+- x509-1.7.5
+- x509-store-1.6.7
+- x509-system-1.6.6
+- x509-validation-1.6.11
+- xml-conduit-1.9.1.1
+- xml-types-0.3.8
+- xss-sanitize-0.3.7
+- yaml-0.11.7.0
+- yesod-1.6.1.2
+- yesod-core-1.6.21.0
+- yesod-form-1.7.0
+- yesod-persistent-1.6.0.7
+- yesod-static-1.6.1.0
+- yesod-test-1.6.12
+- zlib-0.6.2.3
+
+
+# for Shake.hs:
+
+#allow-newer: true
+
+# for precise profiling, per https://www.tweag.io/posts/2020-01-30-haskell-profiling.html:
+# apply-ghc-options: everything
+# rebuild-ghc-options: true
+# stack build --profile --ghc-options="-fno-prof-auto"
+
+# tell GHC to write hie files, eg for weeder. Rumoured to be slow.
+# ghc-options:
+#   "$locals": -fwrite-ide-info
+
+# ghc-options:
+#   "$locals": -ddump-timings
+#  "$targets": -Werror
+#  "$everything": -O2
+#  some-package: -DSOME_CPP_FLAG