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Throwing macro expansion #1142

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Merged
merged 2 commits into from
Dec 14, 2022
Merged

Throwing macro expansion #1142

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f6613e3
Make expansion(of:in:) throwing to match the latest proposal
DougGregor Dec 14, 2022
9cd4529
Use the detach() operation now that it's available.
DougGregor Dec 14, 2022
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2 changes: 1 addition & 1 deletion Sources/_SwiftSyntaxMacros/ExpressionMacro.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -21,5 +21,5 @@ public protocol ExpressionMacro: Macro {
static func expansion(
of node: MacroExpansionExprSyntax,
in context: inout MacroExpansionContext
) -> ExprSyntax
) throws -> ExprSyntax
}
39 changes: 23 additions & 16 deletions Sources/_SwiftSyntaxMacros/Syntax+MacroEvaluation.swift
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Expand Up @@ -13,23 +13,18 @@
import SwiftDiagnostics
import SwiftSyntax

extension MacroExpansionExprSyntax {
private func disconnectedCopy() -> MacroExpansionExprSyntax {
MacroExpansionExprSyntax(
unexpectedBeforePoundToken, poundToken: poundToken,
unexpectedBetweenPoundTokenAndMacro, macro: macro,
genericArguments: genericArguments,
unexpectedBetweenGenericArgumentsAndLeftParen, leftParen: leftParen,
unexpectedBetweenLeftParenAndArgumentList, argumentList: argumentList,
unexpectedBetweenArgumentListAndRightParen, rightParen: rightParen,
unexpectedBetweenRightParenAndTrailingClosure,
trailingClosure: trailingClosure,
unexpectedBetweenTrailingClosureAndAdditionalTrailingClosures,
additionalTrailingClosures: additionalTrailingClosures,
unexpectedAfterAdditionalTrailingClosures
)
/// Diagnostic message used for thrown errors.
struct ThrownErrorDiagnostic: DiagnosticMessage {
let message: String

var severity: DiagnosticSeverity { .error }

var diagnosticID: MessageID {
.init(domain: "SwiftSyntaxMacros", id: "ThrownErrorDiagnostic")
}
}

extension MacroExpansionExprSyntax {
/// Evaluate the given macro for this syntax node, producing the expanded
/// result and (possibly) some diagnostics.
func evaluateMacro(
Expand All @@ -41,7 +36,19 @@ extension MacroExpansionExprSyntax {
}

// Handle the rewrite.
return exprMacro.expansion(of: disconnectedCopy(), in: &context)
do {
return try exprMacro.expansion(of: detach(), in: &context)
} catch {
// Record the error
context.diagnose(
Diagnostic(
node: Syntax(self),
message: ThrownErrorDiagnostic(message: String(describing: error))
)
)

return ExprSyntax(self)
}
}
}

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