let-formatting: Insert hardline in front of the '=' instead of behind (#1302)

Fixes #1301.

Author: sjakobi

dhall/src/Dhall/Pretty/Internal.hs

@@ -541,7 +541,7 @@ prettyCharacterSet characterSet expression =
                 <>  Pretty.align
                     (   renderSrc src0 mempty
                     <>  prettyLabel c <> renderSrc src1 Pretty.hardline
-                    <>  colon <> renderSrc src3 space <> prettyExpression d <> space <> equals <> renderSrc src2 Pretty.hardline
+                    <>  colon <> renderSrc src3 space <> prettyExpression d <> Pretty.hardline <> equals <> renderSrc src2 space
                     <>  prettyExpression e
                     )
 

dhall/tests/format/issue1301A.dhall

@@ -0,0 +1,5 @@
+let attribute
+    : Text → Text → { mapKey : Text, mapValue : Text }
+    = λ(key : Text) → λ(value : Text) → { mapKey = key, mapValue = value }
+
+in  attribute

dhall/tests/format/issue1301B.dhall

@@ -0,0 +1,5 @@
+let attribute
+    : Text → Text → { mapKey : Text, mapValue : Text }
+    = λ(key : Text) → λ(value : Text) → { mapKey = key, mapValue = value }
+
+in  attribute

dhall/tests/format/letLongCommentsB.dhall

@@ -1,5 +1,5 @@
 let x
-    {- foo                                        -} : {- bar                                           -} Bool =
-    {- bla                      -} True
+    {- foo                                        -} : {- bar                                           -} Bool
+    = {- bla                      -} True
 
 in  x

dhall/tests/format/letNewlineCommentsB.dhall

@@ -3,7 +3,7 @@ let x = 1
 in  let {- aaaaaaaaaaaaaaaaaaa
         -} y
         : {- bbbbbbbbbbbbbbbbbbbbb
-          -} Natural =
-        {- ddddddddddddddddd -} 2
+          -} Natural
+        = {- ddddddddddddddddd -} 2
 
     in  x