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fsprojects / fantomas

FSharp source code formatter
https://fsprojects.github.io/fantomas
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Fantomas errors out on `new Foo ""` #1363

Closed Smaug123 closed 3 years ago

Smaug123 commented 3 years ago

I was unable to submit this bug using the online tool ("request too large"), but it does reproduce there.

The following is valid F#:

open System.IO
let f = new StringReader ""

However, Fantomas throws with the following:

System.Exception: Unexpected expression: New
  (false, LongIdent (LongIdentWithDots ([StringReader], [])),
   Const
     (String ("", tmp.fsx (2,25--2,27) IsSynthetic=false),
      tmp.fsx (2,25--2,27) IsSynthetic=false),
   tmp.fsx (2,8--2,27) IsSynthetic=false)
   at Microsoft.FSharp.Core.PrintfModule.PrintFormatToStringThenFail@1433.Invoke(String message) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\printf.fs:line 1433
   at Fantomas.CodePrinter.genExpr(ASTContext astContext, SynExpr synExpr, Context ctx) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 2565
   at Fantomas.Context.shortExpressionWithFallback(FSharpFunc`2 shortExpression, FSharpFunc`2 fallbackExpression, Int32 maxWidth, FSharpOption`1 startColumn, Context ctx) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 782
   at Fantomas.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 441
   at Fantomas.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 441
   at Fantomas.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 441
   at Fantomas.Context.expressionExceedsPageWidth(FSharpFunc`2 beforeShort, FSharpFunc`2 afterShort, FSharpFunc`2 beforeLong, FSharpFunc`2 afterLong, FSharpFunc`2 expr, Context ctx) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 893
   at Fantomas.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 441
   at Fantomas.Context.col[T](FSharpFunc`2 f', IEnumerable`1 c, FSharpFunc`2 f, Context ctx) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 526
   at Fantomas.CodePrinter.genImpFile@96-6.Invoke(Context ctx) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/CodePrinter.fs:line 96
   at Fantomas.Context.op_PlusGreater(FSharpFunc`2 ctx, FSharpFunc`2 f, Context x) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/Context.fs:line 441
   at Fantomas.CodeFormatterImpl.formatWith(ParsedInput ast, FSharpList`1 defines, FSharpList`1 hashTokens, FormatContext formatContext, FormatConfig config) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 395
   at Fantomas.CodeFormatterImpl.format@409-1.Invoke(Tuple`3[] _arg1) in /home/runner/work/fantomas-tools/fantomas-tools/.deps/fantomas/src/Fantomas/CodeFormatterImpl.fs:line 411
   at Microsoft.FSharp.Control.AsyncPrimitives.CallThenInvokeNoHijackCheck[a,b](AsyncActivation`1 ctxt, FSharpFunc`2 userCode, b result1) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 404
   at Microsoft.FSharp.Control.Trampoline.Execute(FSharpFunc`2 firstAction) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\async.fs:line 104

Arguably it should be formatted new StringReader (""); certainly I seem to remember that it's not always valid to omit the parentheses (or, indeed, the space - though I don't know why I seem to remember those).

Smaug123 commented 3 years ago

We can (and probably should!) work around this ourselves in the code we're trying to format, by changing the code to new StringReader(""). I just raised it because it's a bug; it's not very important.