Fix decimal NumberStyles validation (#126644)

Fixes #126643

Also fixes bug in `decimal` similar to #123289

Author: lilinus

src/libraries/System.Private.CoreLib/src/Resources/Strings.resx

@@ -4480,4 +4480,7 @@
   <data name="Argument_FunctionPointersInvalid">
     <value>Function pointer types are not valid.</value>
   </data>
+  <data name="Arg_HexBinaryStylesNotSupported" xml:space="preserve">
+    <value>The number styles AllowHexSpecifier and AllowBinarySpecifier are not supported on the decimal type.</value>
+  </data>
 </root>

src/libraries/System.Private.CoreLib/src/System/Decimal.cs

@@ -534,7 +534,7 @@ public static decimal Parse(string s, NumberStyles style, IFormatProvider? provi
 
         public static decimal Parse(ReadOnlySpan<char> s, NumberStyles style = NumberStyles.Number, IFormatProvider? provider = null)
         {
-            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            NumberFormatInfo.ValidateParseStyleDecimal(style);
             return Number.ParseDecimal(s, style, NumberFormatInfo.GetInstance(provider));
         }
 
@@ -550,7 +550,7 @@ public static decimal Parse(ReadOnlySpan<char> s, NumberStyles style = NumberSty
 
         public static bool TryParse([NotNullWhen(true)] string? s, NumberStyles style, IFormatProvider? provider, out decimal result)
         {
-            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            NumberFormatInfo.ValidateParseStyleDecimal(style);
 
             if (s == null)
             {
@@ -562,7 +562,7 @@ public static bool TryParse([NotNullWhen(true)] string? s, NumberStyles style, I
 
         public static bool TryParse(ReadOnlySpan<char> s, NumberStyles style, IFormatProvider? provider, out decimal result)
         {
-            NumberFormatInfo.ValidateParseStyleFloatingPoint(style);
+            NumberFormatInfo.ValidateParseStyleDecimal(style);
             return Number.TryParseDecimal(s, style, NumberFormatInfo.GetInstance(provider), out result) == Number.ParsingStatus.OK;
         }
 
@@ -1834,14 +1834,14 @@ private static bool TryConvertTo<TOther>(decimal value, [MaybeNullWhen(false)] o
         /// <inheritdoc cref="INumberBase{TSelf}.Parse(ReadOnlySpan{byte}, NumberStyles, IFormatProvider?)" />
         public static decimal Parse(ReadOnlySpan<byte> utf8Text, NumberStyles style = NumberStyles.Number, IFormatProvider? provider = null)
         {
-            NumberFormatInfo.ValidateParseStyleInteger(style);
+            NumberFormatInfo.ValidateParseStyleDecimal(style);
             return Number.ParseDecimal(utf8Text, style, NumberFormatInfo.GetInstance(provider));
         }
 
         /// <inheritdoc cref="INumberBase{TSelf}.TryParse(ReadOnlySpan{byte}, NumberStyles, IFormatProvider?, out TSelf)" />
         public static bool TryParse(ReadOnlySpan<byte> utf8Text, NumberStyles style, IFormatProvider? provider, out decimal result)
         {
-            NumberFormatInfo.ValidateParseStyleInteger(style);
+            NumberFormatInfo.ValidateParseStyleDecimal(style);
             return Number.TryParseDecimal(utf8Text, style, NumberFormatInfo.GetInstance(provider), out result) == Number.ParsingStatus.OK;
         }
 

src/libraries/System.Private.CoreLib/src/System/Globalization/NumberFormatInfo.cs

@@ -846,5 +846,17 @@ static void ThrowInvalid(NumberStyles value)
                 }
             }
         }
+
+        internal static void ValidateParseStyleDecimal(NumberStyles style)
+        {
+            // Check for undefined flags or hex/binary specifiers.
+            if ((style & (InvalidNumberStyles | NumberStyles.AllowHexSpecifier | NumberStyles.AllowBinarySpecifier)) != 0)
+            {
+                ThrowInvalid(style);
+
+                static void ThrowInvalid(NumberStyles value) =>
+                    throw new ArgumentException((value & InvalidNumberStyles) != 0 ? SR.Argument_InvalidNumberStyles : SR.Arg_HexBinaryStylesNotSupported, nameof(style));
+            }
+        }
     }
 }

src/libraries/System.Runtime/tests/System.Globalization.Tests/NumberFormatInfo/NumberFormatInfoValidateParseStyle.cs

@@ -45,5 +45,28 @@ public void ValidateParseStyle_Float(NumberStyles style, bool valid)
                 float.Parse(value, style); // Should not throw
             }
         }
+
+        [Theory]
+        [InlineData(unchecked((NumberStyles)0xFFFFFC00), false)]
+        [InlineData(NumberStyles.HexNumber | NumberStyles.Integer, false)]
+        [InlineData(NumberStyles.AllowHexSpecifier, false)]
+        [InlineData(NumberStyles.HexFloat, false)]
+        [InlineData(NumberStyles.Float, true)]
+        [InlineData(NumberStyles.AllowBinarySpecifier, false)]
+        [InlineData(NumberStyles.AllowHexSpecifier | NumberStyles.AllowExponent, false)]
+        [InlineData(NumberStyles.None, true)]
+        public void ValidateParseStyle_Decimal(NumberStyles style, bool valid)
+        {
+            if (!valid)
+            {
+                AssertExtensions.Throws<ArgumentException>("style", () => decimal.Parse("0", style));
+                AssertExtensions.Throws<ArgumentException>("style", () => decimal.Parse("0"u8, style));
+            }
+            else
+            {
+                decimal.Parse("0", style); // Should not throw
+                decimal.Parse("0"u8, style); // Should not throw
+            }
+        }
     }
 }