[Macros] Implement overloading rules

Author: DougGregor

include/swift/AST/Decl.h

@@ -255,6 +255,9 @@ struct OverloadSignature {
   /// Whether this is a type alias.
   unsigned IsTypeAlias : 1;
 
+  /// Whether this is a macro.
+  unsigned IsMacro : 1;
+
   /// Whether this signature is part of a protocol extension.
   unsigned InProtocolExtension : 1;
 

lib/AST/Decl.cpp

@@ -2785,6 +2785,10 @@ bool swift::conflicting(const OverloadSignature& sig1,
   if (sig1.IsAsyncFunction != sig2.IsAsyncFunction)
     return false;
 
+  // If one is a macro and the other is not, they can't conflict.
+  if (sig1.IsMacro != sig2.IsMacro)
+    return false;
+
   // If one is a compound name and the other is not, they do not conflict
   // if one is a property and the other is a non-nullary function.
   if (sig1.Name.isCompoundName() != sig2.Name.isCompoundName()) {
@@ -3016,6 +3020,7 @@ OverloadSignature ValueDecl::getOverloadSignature() const {
   signature.IsEnumElement = isa<EnumElementDecl>(this);
   signature.IsNominal = isa<NominalTypeDecl>(this);
   signature.IsTypeAlias = isa<TypeAliasDecl>(this);
+  signature.IsMacro = isa<MacroDecl>(this);
   signature.HasOpaqueReturnType =
                        !signature.IsVariable && (bool)getOpaqueResultTypeDecl();
 

test/Macros/macros_diagnostics.swift

@@ -41,6 +41,12 @@ struct ZZZ {
 @expression macro multiArgMacro(_: Any, second: Any) = MissingModule.MissingType
 // expected-note@-1{{'multiArgMacro(_:second:)' declared here}}
 
+@expression macro overloaded1(_ p: P) = MissingModule.MissingType
+func overloaded1(_ p: Any) { }
+
+@expression macro notOverloaded1(_ p: P) = MissingModule.MissingType // expected-note{{'notOverloaded1' previously declared here}}
+@expression macro notOverloaded1(_ p: P) = MissingModule.MissingOtherType // expected-error{{invalid redeclaration of 'notOverloaded1'}}
+
 func testDiags(a: Int, b: Int) {
   // FIXME: Bad diagnostic.
   let s = #stringify<Int, Int>(a + b) // expected-error{{type of expression is ambiguous without more context}}
@@ -59,6 +65,9 @@ func testDiags(a: Int, b: Int) {
 
   _ = stringify(a + b)
   // expected-error@-1{{expansion of macro 'stringify' requires leading '#'}}{{7-7=#}}
+
+  overloaded1(a) // okay, calls the function
+  #overloaded1(a) // expected-error{{argument type 'Int' does not conform to expected type 'P'}}
 }
 
 func shadow(a: Int, b: Int, stringify: Int) {