Add support for SynExpr.LibraryOnlyStaticOptimization. Fixes #1769. (#…

…1788)

src/Fantomas.Tests/Fantomas.Tests.fsproj

@@ -89,6 +89,7 @@
     <Compile Include="ColMultilineItemTests.fs" />
     <Compile Include="BarBeforeDiscriminatedUnionDeclarationTests.fs" />
     <Compile Include="SpaceBeforeColonTests.fs" />
+    <Compile Include="LibraryOnlySynExprTests.fs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Fantomas.Extras\Fantomas.Extras.fsproj" />

src/Fantomas.Tests/LibraryOnlySynExprTests.fs

@@ -0,0 +1,22 @@
+module Fantomas.Tests.LibraryOnlySynExprTests
+
+open NUnit.Framework
+open FsUnit
+open Fantomas.Tests.TestHelper
+
+[<Test>]
+let ``SynExpr.LibraryOnlyStaticOptimization`` () =
+    formatSourceString
+        false
+        """
+     let FromZero () : 'T =
+                (get32 0 :?> 'T) when 'T : BigInteger = BigInteger.Zero
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+let FromZero () : 'T =
+    (get32 0 :?> 'T) when 'T: BigInteger = BigInteger.Zero
+"""

src/Fantomas/CodePrinter.fs

@@ -2426,6 +2426,13 @@ and genExpr astContext synExpr ctx =
                     r.EndLine
                     (r.EndColumn + 1)
             )
+
+        | LibraryOnlyStaticOptimization (optExpr, constraints, e) ->
+            genExpr astContext optExpr
+            +> genSynStaticOptimizationConstraint astContext constraints
+            +> sepEq
+            +> sepSpaceOrNlnIfExpressionExceedsPageWidth (genExpr astContext e)
+
         | UnsupportedExpr r ->
             raise
             <| FormatException(
@@ -5540,6 +5547,22 @@ and genConstBytes (bytes: byte []) (r: Range) =
         | None -> !-(sprintf "%A" bytes)
         <| ctx
 
+and genSynStaticOptimizationConstraint
+    (astContext: ASTContext)
+    (constraints: SynStaticOptimizationConstraint list)
+    : Context -> Context =
+    let genConstraint astContext con =
+        match con with
+        | SynStaticOptimizationConstraint.WhenTyparTyconEqualsTycon (t1, t2, _) ->
+            genTypar astContext t1
+            +> sepColon
+            +> sepSpace
+            +> genType astContext false t2
+        | SynStaticOptimizationConstraint.WhenTyparIsStruct (t, _) -> genTypar astContext t
+
+    !- " when "
+    +> col sepSpace constraints (genConstraint astContext)
+
 and genTriviaFor (mainNodeName: FsAstType) (range: Range) f ctx =
     (enterNodeFor mainNodeName range
      +> f

src/Fantomas/SourceParser.fs

@@ -1092,10 +1092,14 @@ let (|ILEmbedded|_|) =
     | SynExpr.LibraryOnlyILAssembly (_, _, _, _, r) -> Some(r)
     | _ -> None
 
+let (|LibraryOnlyStaticOptimization|_|) (e: SynExpr) =
+    match e with
+    | SynExpr.LibraryOnlyStaticOptimization (constraints, e, optExpr, _) -> Some(optExpr, constraints, e)
+    | _ -> None
+
 let (|UnsupportedExpr|_|) =
     function
-    // Temprorarily ignore these cases not often used outside FSharp.Core
-    | SynExpr.LibraryOnlyStaticOptimization (_, _, _, r)
+    // Temporarily ignore these cases not often used outside FSharp.Core
     | SynExpr.LibraryOnlyUnionCaseFieldGet (_, _, _, r)
     | SynExpr.LibraryOnlyUnionCaseFieldSet (_, _, _, _, r) -> Some r
     | _ -> None