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[DRAFT] Allow a default for optional interpolations #80547

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[DRAFT] Allow a default for optional interpolations #80547

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2 changes: 2 additions & 0 deletions include/swift/AST/DiagnosticsSema.def
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Original file line number Diff line number Diff line change
Expand Up @@ -4958,6 +4958,8 @@ NOTE(iuo_to_any_coercion_note_func_result,none,
(const ValueDecl *))
NOTE(default_optional_to_any,none,
"provide a default value to avoid this warning", ())
NOTE(default_optional_parameter,none,
"provide a default value parameter", ())
NOTE(force_optional_to_any,none,
"force-unwrap the value to avoid this warning", ())
NOTE(silence_optional_to_any,none,
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5 changes: 5 additions & 0 deletions lib/Sema/MiscDiagnostics.cpp
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Expand Up @@ -5688,6 +5688,11 @@ static void diagnoseUnintendedOptionalBehavior(const Expr *E,
.fixItInsertAfter(arg->getEndLoc(), ")");

if (kind == UnintendedInterpolationKind::Optional) {
// Suggest using a default interpolation value parameter.
Ctx.Diags.diagnose(arg->getLoc(), diag::default_optional_parameter)
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@beccadax Do you know if it would be possible to only provide this fixit when the string interpolation type is DefaultStringInterpolation?

.highlight(arg->getSourceRange())
.fixItInsertAfter(arg->getEndLoc(), ", default: <#default value#>");

// Suggest inserting a default value.
Ctx.Diags.diagnose(arg->getLoc(), diag::default_optional_to_any)
.highlight(arg->getSourceRange())
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40 changes: 40 additions & 0 deletions stdlib/public/core/StringInterpolation.swift
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Expand Up @@ -197,6 +197,46 @@ public struct DefaultStringInterpolation: StringInterpolationProtocol, Sendable
}
}

extension DefaultStringInterpolation {
@backDeployed(before: SwiftStdlib 6.2)
public mutating func appendInterpolation<T>(
_ value: T?,
default: @autoclosure () -> String
) where T: TextOutputStreamable {
if let value {
self.appendInterpolation(value)
} else {
self.appendInterpolation(`default`())
}
}

@backDeployed(before: SwiftStdlib 6.2)
@_disfavoredOverload
public mutating func appendInterpolation<T>(
_ value: T?,
default: @autoclosure () -> String
) where T: CustomStringConvertible {
if let value {
self.appendInterpolation(value)
} else {
self.appendInterpolation(`default`())
}
}

@backDeployed(before: SwiftStdlib 6.2)
@_disfavoredOverload
public mutating func appendInterpolation<T>(
_ value: T?,
default: @autoclosure () -> String
) {
if let value {
self.appendInterpolation(value)
} else {
self.appendInterpolation(`default`())
}
}
}

extension DefaultStringInterpolation: CustomStringConvertible {
@inlinable
public var description: String {
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12 changes: 8 additions & 4 deletions test/Sema/diag_unintended_optional_behavior.swift
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Expand Up @@ -200,17 +200,20 @@ func warnOptionalInStringInterpolationSegment(_ o : Int?) {
print("Always some, Always some, Always some: \(o)")
// expected-warning@-1 {{string interpolation produces a debug description for an optional value; did you mean to make this explicit?}}
// expected-note@-2 {{use 'String(describing:)' to silence this warning}} {{51-51=String(describing: }} {{52-52=)}}
// expected-note@-3 {{provide a default value to avoid this warning}} {{52-52= ?? <#default value#>}}
// expected-note@-3 {{provide a default value parameter}} {{52-52=, default: <#default value#>}}
// expected-note@-4 {{provide a default value to avoid this warning}} {{52-52= ?? <#default value#>}}
var i: Int? = o
print("Always some, Always some, Always some: \(i)")
// expected-warning@-1 {{string interpolation produces a debug description for an optional value; did you mean to make this explicit?}}
// expected-note@-2 {{use 'String(describing:)' to silence this warning}} {{51-51=String(describing: }} {{52-52=)}}
// expected-note@-3 {{provide a default value to avoid this warning}} {{52-52= ?? <#default value#>}}
// expected-note@-3 {{provide a default value parameter}} {{52-52=, default: <#default value#>}}
// expected-note@-4 {{provide a default value to avoid this warning}} {{52-52= ?? <#default value#>}}
i = nil
print("Always some, Always some, Always some: \(o.map { $0 + 1 })")
// expected-warning@-1 {{string interpolation produces a debug description for an optional value; did you mean to make this explicit?}}
// expected-note@-2 {{use 'String(describing:)' to silence this warning}} {{51-51=String(describing: }} {{67-67=)}}
// expected-note@-3 {{provide a default value to avoid this warning}} {{67-67= ?? <#default value#>}}
// expected-note@-3 {{provide a default value parameter}} {{67-67=, default: <#default value#>}}
// expected-note@-4 {{provide a default value to avoid this warning}} {{67-67= ?? <#default value#>}}

print("Always some, Always some, Always some: \(o as Int?)") // No warning
print("Always some, Always some, Always some: \(o.debugDescription)") // No warning.
Expand All @@ -222,7 +225,8 @@ func warnOptionalInStringInterpolationSegment(_ o : Int?) {
print("Always some, Always some, Always some: \(ooST)")
// expected-warning@-1 {{string interpolation produces a debug description for an optional value; did you mean to make this explicit?}}
// expected-note@-2 {{use 'String(describing:)' to silence this warning}} {{51-51=String(describing: }} {{55-55=)}}
// expected-note@-3 {{provide a default value to avoid this warning}} {{55-55= ?? <#default value#>}}
// expected-note@-3 {{provide a default value parameter}} {{55-55=, default: <#default value#>}}
// expected-note@-4 {{provide a default value to avoid this warning}} {{55-55= ?? <#default value#>}}
}

// Make sure we don't double diagnose
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15 changes: 15 additions & 0 deletions test/stdlib/PrintString.swift
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Expand Up @@ -92,6 +92,11 @@ PrintTests.test("StringInterpolation") {

let s2 = "aaa\(1)bbb\(2 as Any)"
expectEqual("aaa1bbb2", s2)

let x: Int? = 1
let y: Int? = nil
let s3 = "aaa\(x, default: "NONE")bbb\(y, default: "NONE")"
expectEqual("aaa1bbbNONE", s3)
}

PrintTests.test("SubstringInterpolation") {
Expand All @@ -100,6 +105,11 @@ PrintTests.test("SubstringInterpolation") {

let s2 = "aaa\(1)bbb\(2 as Any)" as Substring
expectEqual("aaa1bbb2", s2)

let x: Int? = 1
let y: Int? = nil
let s3 = "aaa\(x, default: "NONE")bbb\(y, default: "NONE")" as Substring
expectEqual("aaa1bbbNONE", s3)
}

PrintTests.test("CustomStringInterpolation") {
Expand All @@ -116,6 +126,11 @@ PrintTests.test("AutoCustomStringInterpolation") {

let s2 = ("aaa\(1)bbb\(2 as Any)" as MySimpleString).value
expectEqual("aaa1bbb2", s2)

let x: Int? = 1
let y: Int? = nil
let s3 = ("aaa\(x, default: "NONE")bbb\(y, default: "NONE")" as MySimpleString).value
expectEqual("aaa1bbbNONE", s3)
}

PrintTests.test("CustomStringInterpolationExtra") {
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