Fixing up the Double/Single parsing code to be correct (dotnet#20707)

* Don't normalize -0.0 to 0.0 when parsing

* Updating NumberBuffer to validate the constructor inputs

* Updating NumberToDouble to just get the precision

* Don't check for non-significant zero's in NumberToDouble

* Updating Number.BigInteger to carry additional space for the worst-case scenario

* Removing some dead code from double.TryParse

* Updating NumberToDouble to use the RealParser implementation from Roslyn

* Fixing TryNumberToDouble and TryNumberToSingle to apply the appropriate sign.

* Adding a fast path for double/single parsing when we have <= 15 digits and an absolute scale <= 22

* Update NumberBuffer to also track whether any input digits past maxDigCount were non-zero

* Renaming NumberToFloatingPointBitsRoslyn to NumberToFloatingPointBits

* Updating TryNumberToDouble and TryNumberToSingle to support Overflow to Infinity

* Fixing a Debug.Assert in TryParseNumber

* Fixing `DecimalNumberBufferLength` to 30

* Renaming NumberToFloatingPointBitsRoslyn to NumberToFloatingPointBits

* Clarifying the NumberBufferLength comments

* Fixing TryNumberToDecimal to check the last digit in the buffer, if it exists

* Disable some CoreFX tests due to the single/double/decimal parsing fixes

* Fix TryNumberToDecimal to not modify the value of p in the assert.

Co-Authored-By: tannergooding <[email protected]>

* Updating NumberToFloatingPointBits to use single-precision arithmetic and extended-precision multiplication where possible

* Splitting the NumberToFloatingPointBits code into a fast and slow-path method

* Ensure Roslyn is properly attributed.

* Removing the 80-bit extended precision fast path for NumberToFloatingPointBits, due to a bug

* Fixing the double and single parser to ignore case for Infinity and NaN

* Add a clarifying comment to Number.NumberToFloatingPointBits that the code has been modified from the original source.

* Removing the remaining code that was used by the 80-bit extended precision fast-path in NumberToFloatingPointBits

* Adding a missing comma to the CoreFX.issues.json

* Remove licensing "glue" and re-release the Roslyn RealParser code under the MIT license.

* Some minor cleanup to the NumberToFloatingPointBits code.

Signed-off-by: dotnet-bot <[email protected]>

Author: tannergooding

src/Common/src/CoreLib/System.Private.CoreLib.Shared.projitems

@@ -294,7 +294,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.Formatting.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.Grisu3.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.NumberBuffer.cs" />
-    <Compile Include="$(MSBuildThisFileDirectory)System\Number.NumberToDouble.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)System\Number.NumberToFloatingPointBits.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\Number.Parsing.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\NullReferenceException.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)System\ObjectDisposedException.cs" />

src/Common/src/CoreLib/System/Double.cs

@@ -341,28 +341,7 @@ public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatPro
 
         private static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, NumberFormatInfo info, out double result)
         {
-            bool success = Number.TryParseDouble(s, style, info, out result, out _);
-            if (!success)
-            {
-                ReadOnlySpan<char> sTrim = s.Trim();
-                if (sTrim.EqualsOrdinal(info.PositiveInfinitySymbol))
-                {
-                    result = PositiveInfinity;
-                }
-                else if (sTrim.EqualsOrdinal(info.NegativeInfinitySymbol))
-                {
-                    result = NegativeInfinity;
-                }
-                else if (sTrim.EqualsOrdinal(info.NaNSymbol))
-                {
-                    result = NaN;
-                }
-                else
-                {
-                    return false; // We really failed
-                }
-            }
-            return true;
+            return Number.TryParseDouble(s, style, info, out result);
         }
 
         //