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Accept number, char, bool and %s holes in constant interpolated strings - #20754
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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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An interpolated string whose holes are non-null constant strings without alignment or format specifiers now folds to its text where F# requires a constant: [<Literal>] values (also in signatures), attribute arguments and type provider static arguments. It was rejected with FS0267, so a constant built from other constants needed '+'. The checker marks those three contexts in TcEnv and folds the string there. Everywhere else, quotations included, interpolated strings are still lowered to String.Concat. A hole that breaks a rule reports FS3925 at the hole; a hole that is not a constant reports FS0267 at the hole. Gated on the ConstantInterpolatedStrings preview feature. Language suggestion dotnet#1347 RFC FS-1352 Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
RFC FS-1352 reports the rule error on the first hole that breaks a rule.
Later holes are still type-checked, but are no longer evaluated as
constants, so '$"{1}{2}"' gives FS3925 once instead of once per hole.
Reword FS3925 to the RFC's "must be a constant": the message is shown
when a hole keeps the string from being one.
Cover type provider static arguments, after 'const' and through a
literal, with a provider that returns its string static argument.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Review follow-up. The hole text comes from a top-level tryConstantHoleText,
every hole is type-checked before the first one is evaluated (so a later
undefined name is still reported), and the constant path runs only when the
ConstantInterpolatedStrings feature is supported: before the preview language
version an interpolated string in a literal is checked as before, so a branch
that is never evaluated, such as false && ($"{1}" = "1"), stays valid.
The type provider test uses a small fixture that checks the argument it
receives: the helloWorld provider overflows the stack of the test host when it
is compiled in process. One language release note remains.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Unlike C#, F# formats integers, decimals, characters and Booleans in
interpolated strings with the invariant culture, so their text is known at
compile time. A constant interpolated string now also accepts such holes, and a
plain '%s' hole on a constant string, as asked in the RFC FS-1352 discussion:
the folded text is the text 'string' gives at run time ("True" for true,
"1.50" for 1.50m).
Float holes stay excluded: their text depends on the runtime the compiler runs
on (-0.0 is "0" on .NET Framework and "-0" on .NET). Enum holes stay excluded
too.
RFC FS-1352 amendment
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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Stacked on #20753
A constant interpolated string also accepts integer,
decimal,charandboolholes and a plain%shole. F# formats these with the invariant culture, so the folded text is the run-time text:$"v{2}-{true}"is"v2-True". Float holes stay rejected, because their text depends on the runtime that runs the compiler (-0.0is0on .NET Framework and-0on .NET).Details