[Issue 1620] New: std.conv.to fails for integer unsigned->signed conversion

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=1620

           Summary: std.conv.to fails for integer unsigned->signed
                    conversion
           Product: D
           Version: 2.006
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: i.kasiuk at gmx.de


A conversion like to!(int)(123u) fails, producing the following error at
runtime:

Error: Error: overflow Conversion underflow


Here is the code from conv.d which does the check:

  static const

      sSmallest = isFloatingPoint!(S) ? -S.max : S.min,

      tSmallest = isFloatingPoint!(T) ? -T.max : T.min;

  static if (sSmallest < tSmallest) {

    // possible underflow

    if (value < tSmallest) conv_overflow("Conversion underflow");

  }

  ...


This apparently doesn't work as intended because of the implicit conversions
happening when the values are compared.

Actually, why does the compiler silently do an implicit type conversion here? I
think this is a bit unfortunate.


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