#62 TryVar2Single/TryVar2Dbl/TryVar2Ext/TryVar2Str raise instead of returning False

[Thomas Mueller]

In u_dzVariantUtils, TryVar2Single, TryVar2Dbl, TryVar2Ext and TryVar2Str catch the EVariantError of a variant that cannot be converted (e.g. the string 'abc' to Double, or a variant array to string) and raise EVariantConvertError instead of returning False. Their doc comments even say so ("@raises EVariantConvertError if there is some other conversion error").

TryVar2Int, TryVar2Int64, TryVar2LongWord and TryVar2Bool return False in the same case.

This also breaks the functions built on them:

• Var2Dbl, Var2Ext, Var2DblStr and Var2Str promise to return the default (or NullValue) if the variant cannot be converted, but raise.
• TryVar2Number in u_dzNullableTypesUtils, so the AssignVariant of a nullable Single/Double/Extended raises where a nullable Int32/Int64 becomes Null.

Fix: return False, like the integer and Boolean siblings. Callers that want the exception have Var2DblEx, Var2ExtEx and Var2StrEx.

[Thomas Mueller]

Not a bug, the exception is intended: TryVar2Xxx returns False only for a Null or Empty variant, a variant that holds something that cannot be converted raises EVariantConvertError. The comment above the conversion functions has said so since the initial import.

The functions that deviate are TryVar2Int, TryVar2Int64, TryVar2LongWord and TryVar2Bool, which return False in that case. That is [#63].