Sema: Form pack expansion types in simplifyTypeExpr()

Author: slavapestov

lib/Sema/PreCheckExpr.cpp

@@ -2018,6 +2018,15 @@ TypeExpr *PreCheckExpression::simplifyTypeExpr(Expr *E) {
     return new (Ctx) TypeExpr(CompRepr);
   }
 
+  // Fold 'T...' into a pack expansion type when 'T' is a TypeExpr.
+  if (auto *operand = isPostfixEllipsisOperator(E)) {
+    if (auto *pattern = dyn_cast<TypeExpr>(operand)) {
+      auto *repr = new (Ctx) PackExpansionTypeRepr(pattern->getTypeRepr(),
+                                                   E->getLoc());
+      return new (Ctx) TypeExpr(repr);
+    }
+  }
+
   return nullptr;
 }
 

test/Constraints/variadic_generic_types.swift

@@ -0,0 +1,25 @@
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature VariadicGenerics
+
+// REQUIRES: asserts
+
+// Parsing an UnresolvedSpecializeExpr containing a PackExpansionType
+struct G<T...> {}
+
+func f<T...>(_: T...) {
+  _ = G< >.self
+  _ = G<Int>.self
+  _ = G<Int, String>.self
+  _ = G<T... >.self
+  _ = G<Int, (Array<T>)... >.self
+}
+
+// Forming PackExpansionTypeReprs in simplifyTypeExpr()
+func g<T...>(_: T...) {
+  _ = (T...).self
+  _ = (Int, T...).self
+  _ = ((T...) -> ()).self
+  _ = ((Int, (Array<T>)...) -> ()).self
+
+  _ = (Int...).self // expected-error {{variadic expansion 'Int' must contain at least one variadic generic parameter}}
+}
+

test/SILGen/pack_expansion_type.swift

@@ -15,4 +15,29 @@ public struct VariadicType<T...> {
   // CHECK-LABEL: sil [ossa] @$s19pack_expansion_type12VariadicTypeV13takesFunction1tyqd__qd__Qp_txxQpXE_tlF : $@convention(method) <T...><U...> (@noescape @callee_guaranteed @substituted <τ_0_0..., τ_0_1..., τ_0_2..., τ_0_3...> (@in_guaranteed τ_0_0...) -> @out τ_0_2... for <T, T, U, U>, VariadicType<T...>) -> () {
   // CHECK: bb0(%0 : $@noescape @callee_guaranteed @substituted <τ_0_0..., τ_0_1..., τ_0_2..., τ_0_3...> (@in_guaranteed τ_0_0...) -> @out τ_0_2... for <T, T, U, U>, %1 : $VariadicType<T...>):
   public func takesFunction<U...>(t: (T...) -> (U...)) {}
+}
+
+// CHECK-LABEL: sil hidden [ossa] @$s19pack_expansion_type17variadicMetatypesyyxxQplF : $@convention(thin) <T...> (@in_guaranteed T...) -> () {
+// CHECK: bb0(%0 : $*T...):
+// CHECK: metatype $@thin VariadicType<>.Type
+// CHECK: metatype $@thin VariadicType<Int>.Type
+// CHECK: metatype $@thin VariadicType<Int, String>.Type
+// CHECK: metatype $@thin VariadicType<T...>.Type
+// CHECK: metatype $@thin VariadicType<Int, Array<T>...>.Type
+// CHECK: metatype $@thin (T...).Type
+// CHECK: metatype $@thin (Int, Array<T>...).Type
+// CHECK: metatype $@thin ((T...) -> ()).Type
+// CHECK: metatype $@thin ((Int, Array<T>...) -> ()).Type
+// CHECK: return
+
+func variadicMetatypes<T...>(_: T...) {
+  _ = VariadicType< >.self
+  _ = VariadicType<Int>.self
+  _ = VariadicType<Int, String>.self
+  _ = VariadicType<T... >.self
+  _ = VariadicType<Int, (Array<T>)... >.self
+  _ = (T...).self
+  _ = (Int, (Array<T>)...).self
+  _ = ((T...) -> ()).self
+  _ = ((Int, (Array<T>)...) -> ()).self
 }