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[Macros] Don't allow macros to add accessors to let variables. #73878

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Merged
merged 1 commit into from
May 24, 2024
Merged

[Macros] Don't allow macros to add accessors to let variables. #73878

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3 changes: 3 additions & 0 deletions include/swift/AST/DiagnosticsSema.def
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Original file line number Diff line number Diff line change
Expand Up @@ -7618,6 +7618,9 @@ ERROR(external_macro_arg_not_type_name,none,
ERROR(invalid_decl_in_macro_expansion,none,
"macro expansion cannot introduce %0",
(DescriptiveDeclKind))
ERROR(let_accessor_expansion,none,
"cannot expand accessors on variable declared with 'let'",
())
ERROR(invalid_main_type_in_macro_expansion,none,
"macro expansion cannot introduce '@main' type",
())
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16 changes: 13 additions & 3 deletions lib/Sema/TypeCheckMacros.cpp
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Expand Up @@ -739,12 +739,12 @@ static void validateMacroExpansion(SourceFile *expansionBuffer,
};

for (auto item : expansionBuffer->getTopLevelItems()) {
auto &ctx = expansionBuffer->getASTContext();
auto *decl = item.dyn_cast<Decl *>();
if (!decl) {
if (role != MacroRole::CodeItem &&
role != MacroRole::Preamble &&
role != MacroRole::Body) {
auto &ctx = expansionBuffer->getASTContext();
ctx.Diags.diagnose(item.getStartLoc(),
diag::expected_macro_expansion_decls);
}
Expand All @@ -753,8 +753,18 @@ static void validateMacroExpansion(SourceFile *expansionBuffer,
}

// Certain macro roles can generate special declarations.
if ((isa<AccessorDecl>(decl) && role == MacroRole::Accessor) ||
(isa<ExtensionDecl>(decl) && role == MacroRole::Conformance)) {
if (isa<AccessorDecl>(decl) && role == MacroRole::Accessor) {
auto *var = dyn_cast<VarDecl>(attachedTo);
if (var && var->isLet()) {
ctx.Diags.diagnose(var->getLoc(),
diag::let_accessor_expansion)
.warnUntilSwiftVersion(6);
}

continue;
}

if (isa<ExtensionDecl>(decl) && role == MacroRole::Conformance) {
continue;
}

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9 changes: 9 additions & 0 deletions test/Macros/Inputs/syntax_macro_definitions.swift
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Expand Up @@ -2482,3 +2482,12 @@ public struct AllLexicalContextsMacro: DeclarationMacro {
}
}

public struct AddGetterMacro: AccessorMacro {
public static func expansion(
of node: AttributeSyntax,
providingAccessorsOf declaration: some DeclSyntaxProtocol,
in context: some MacroExpansionContext
) throws -> [AccessorDeclSyntax] {
return ["get { 0 }"]
}
}
11 changes: 11 additions & 0 deletions test/Macros/accessor_macros.swift
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Expand Up @@ -163,3 +163,14 @@ struct MultipleVars {
// expected-error@-1 2{{accessor macro 'AddWillSet()' can only apply to a single variable}}
}
#endif

@attached(accessor)
macro addGetterMacro() =
#externalMacro(module: "MacroDefinition", type: "AddGetterMacro")

#if TEST_DIAGNOSTICS
struct S {
@addGetterMacro let x: Int
// expected-warning@-1 {{cannot expand accessors on variable declared with 'let'; this is an error in the Swift 6 language mode}}
}
#endif