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Improve diagnostic for @Flag Bool? without inversion: #892

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Merged
rauhul merged 2 commits into from
Apr 23, 2026
+18 −0
Merged

Improve diagnostic for @Flag Bool? without inversion: #892

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796f502
Improve diagnostic for @Flag Bool? without inversion:
qflen Apr 21, 2026
c82827c
escape  _name  so it renders correctly in documentation
qflen Apr 22, 2026
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18 changes: 18 additions & 0 deletions Sources/ArgumentParser/Parsable Properties/Flag.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -251,6 +251,24 @@ extension Flag where Value == Bool? {
exclusivity: exclusivity,
help: help)
}

/// Surfaces a clearer diagnostic when a user declares a `Bool?` flag without
/// the required `inversion:` parameter.
///
/// Without this overload, the compiler falls back to the
/// `Flag where Value == Int` initializer and reports a confusing
/// "types 'Bool?' and 'Int' be equivalent" error.
@available(
*, unavailable,
message:
"An optional 'Bool?' @Flag requires an 'inversion:' parameter, such as '.prefixedNo' or '.prefixedEnableDisable'."
)
public init(
name _name: NameSpecification = .long,
help: ArgumentHelp? = nil
) {
fatalError("unavailable")
}
}

extension Flag where Value == Bool {
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