Support data types with infix & multi-line declarations

Fix the bug where data types with infix names & names layed out over multiple lines get incorrectly formatted. Specifically, reuse `p_infixDefHelper` to easily take care of this behavior.

data/examples/declaration/data/multiline-names-out.hs

@@ -0,0 +1,29 @@
+data
+  Foo
+    a
+    b
+  = Foo a b
+
+data a :-> b = Arrow (a -> b)
+
+data (f :* g) a = f a :* g a
+
+data
+  ( f :+
+    g
+  )
+    a
+  = L (f a)
+  | R (g a)
+
+data a `Arrow` b = Arrow' (a -> b)
+
+data (f `Product` g) a = f a `Product` g a
+
+data
+  ( f `Sum`
+    g
+  )
+    a
+  = L' (f a)
+  | R' (g a)

data/examples/declaration/data/multiline-names.hs

@@ -0,0 +1,23 @@
+data Foo a
+         b
+  = Foo a b
+
+data a :-> b = Arrow (a -> b)
+
+data (f :* g) a = f a :* g a
+
+data (f
+      :+
+      g)
+  a = L (f a)
+    | R (g a)
+
+data a `Arrow` b = Arrow' (a -> b)
+
+data (f `Product` g) a = f a `Product` g a
+
+data (f
+      `Sum`
+      g)
+  a = L' (f a)
+    | R' (g a)

data/examples/declaration/instance/associated-data-out.hs

@@ -6,7 +6,9 @@ instance Foo Int where
 
 instance Foo Double where
 
-  newtype Bar Double
+  newtype
+    Bar
+      Double
     = DoubleBar
         Double
         Double

data/examples/declaration/instance/data-family-instances-out.hs

@@ -3,7 +3,9 @@
 
 data instance Foo Int = FooInt Int
 
-data instance Foo [Int]
+data instance
+  Foo
+    [Int]
   = IntListFoo
       ( Int
       , Int

src/Ormolu/Printer/Meat/Declaration.hs

@@ -66,7 +66,12 @@ p_tyClDecl style = \case
   FamDecl NoExt x -> p_famDecl style x
   SynDecl {..} -> p_synDecl tcdLName tcdTyVars tcdRhs
   DataDecl {..} ->
-    p_dataDecl Associated tcdLName (tyVarsToTypes tcdTyVars) tcdDataDefn
+    p_dataDecl
+      Associated
+      tcdLName
+      (tyVarsToTypes tcdTyVars)
+      tcdFixity
+      tcdDataDefn
   ClassDecl {..} ->
     p_classDecl
       tcdCtxt

src/Ormolu/Printer/Meat/Declaration/Data.hs

@@ -24,18 +24,24 @@ p_dataDecl
   :: FamilyStyle                -- ^ Whether to format as data family
   -> Located RdrName            -- ^ Type constructor
   -> [LHsType GhcPs]            -- ^ Type patterns
+  -> LexicalFixity              -- ^ Lexical fixity
   -> HsDataDefn GhcPs           -- ^ Data definition
   -> R ()
-p_dataDecl style name tpats HsDataDefn {..} = do
+p_dataDecl style name tpats fixity HsDataDefn {..} = do
+  let combinedSpans = combineSrcSpans' (getLoc name :| (getLoc <$> tpats))
   txt $ case dd_ND of
-    NewType -> "newtype "
-    DataType -> "data "
+    NewType -> "newtype"
+    DataType -> "data"
   txt $ case style of
     Associated -> mempty
-    Free -> "instance "
-  p_rdrName name
-  unless (null tpats) space
-  spaceSep (located' p_hsType) tpats
+    Free -> " instance"
+  switchLayout combinedSpans $ do
+    breakpoint
+    inci $ p_infixDefHelper
+      (isInfix fixity)
+      inci
+      (p_rdrName name)
+      (located' p_hsType <$> tpats)
   case dd_kindSig of
     Nothing -> return ()
     Just k -> do
@@ -58,7 +64,7 @@ p_dataDecl style name tpats HsDataDefn {..} = do
   newline
   inci . located dd_derivs $ \xs ->
     forM_ xs (line . located' p_hsDerivingClause)
-p_dataDecl _ _ _ (XHsDataDefn NoExt) = notImplemented "XHsDataDefn"
+p_dataDecl _ _ _ _ (XHsDataDefn NoExt) = notImplemented "XHsDataDefn"
 
 p_conDecl :: ConDecl GhcPs -> R ()
 p_conDecl = \case
@@ -165,3 +171,11 @@ p_hsDerivingClause HsDerivingClause {..} = do
       ViaStrategy (XHsImplicitBndrs NoExt) ->
         notImplemented "XHsImplicitBndrs"
 p_hsDerivingClause (XHsDerivingClause NoExt) = notImplemented "XHsDerivingClause"
+
+----------------------------------------------------------------------------
+-- Helpers
+
+isInfix :: LexicalFixity -> Bool
+isInfix = \case
+  Infix -> True
+  Prefix -> False

src/Ormolu/Printer/Meat/Declaration/Instance.hs

@@ -112,7 +112,7 @@ p_dataFamInstDecl style = \case
   DataFamInstDecl {..} -> do
     let HsIB {..} = dfid_eqn
         FamEqn {..} = hsib_body
-    p_dataDecl style feqn_tycon feqn_pats feqn_rhs
+    p_dataDecl style feqn_tycon feqn_pats feqn_fixity feqn_rhs
 
 match_overlap_mode :: Maybe (Located OverlapMode) -> R () -> R ()
 match_overlap_mode overlap_mode layoutStrategy =