Merge pull request swiftlang#78248 from Azoy/value-generic-static-member

[NameLookup] Allow value generics to show up as static members

Author: Azoy

include/swift/AST/Expr.h

@@ -1449,23 +1449,25 @@ class TypeExpr : public Expr {
 };
 
 class TypeValueExpr : public Expr {
-  GenericTypeParamDecl *paramDecl;
-  DeclNameLoc loc;
+  TypeRepr *repr;
   Type paramType;
 
-  /// Create a \c TypeValueExpr from a given generic value param decl.
-  TypeValueExpr(DeclNameLoc loc, GenericTypeParamDecl *paramDecl) :
-      Expr(ExprKind::TypeValue, /*implicit*/ false), paramDecl(paramDecl),
-      loc(loc), paramType(nullptr) {}
+  /// Create a \c TypeValueExpr from a given type representation.
+  TypeValueExpr(TypeRepr *repr) :
+      Expr(ExprKind::TypeValue, /*implicit*/ false), repr(repr),
+      paramType(nullptr) {}
 
 public:
-  /// Create a \c TypeValueExpr for a given \c GenericTypeParamDecl.
+  /// Create a \c TypeValueExpr for a given \c TypeDecl.
   ///
   /// The given location must be valid.
-  static TypeValueExpr *createForDecl(DeclNameLoc Loc, GenericTypeParamDecl *D);
+  static TypeValueExpr *createForDecl(DeclNameLoc loc, TypeDecl *d,
+                                      DeclContext *dc);
 
-  GenericTypeParamDecl *getParamDecl() const {
-    return paramDecl;
+  GenericTypeParamDecl *getParamDecl() const;
+
+  TypeRepr *getRepr() const {
+    return repr;
   }
 
   /// Retrieves the corresponding parameter type of the value referenced by this
@@ -1480,9 +1482,7 @@ class TypeValueExpr : public Expr {
     this->paramType = paramType;
   }
 
-  SourceRange getSourceRange() const {
-    return loc.getSourceRange();
-  }
+  SourceRange getSourceRange() const;
 
   static bool classof(const Expr *E) {
     return E->getKind() == ExprKind::TypeValue;

include/swift/Basic/Features.def

@@ -256,6 +256,7 @@ LANGUAGE_FEATURE(RawIdentifiers, 451, "Raw identifiers")
 LANGUAGE_FEATURE(SendableCompletionHandlers, 463, "Objective-C completion handler parameters are imported as @Sendable")
 LANGUAGE_FEATURE(AsyncExecutionBehaviorAttributes, 0, "@concurrent and nonisolated(nonsending)")
 LANGUAGE_FEATURE(IsolatedConformances, 407, "Global-actor isolated conformances")
+LANGUAGE_FEATURE(ValueGenericsNameLookup, 452, "Value generics appearing as static members for namelookup")
 
 // Swift 6
 UPCOMING_FEATURE(ConciseMagicFile, 274, 6)

lib/AST/Expr.cpp

@@ -2441,11 +2441,22 @@ bool Expr::isSelfExprOf(const AbstractFunctionDecl *AFD, bool sameBase) const {
   return false;
 }
 
-TypeValueExpr *TypeValueExpr::createForDecl(DeclNameLoc loc, 
-                                            GenericTypeParamDecl *paramDecl) {
-  auto &ctx = paramDecl->getASTContext();
+TypeValueExpr *TypeValueExpr::createForDecl(DeclNameLoc loc, TypeDecl *decl,
+                                            DeclContext *dc) {
+  auto &ctx = decl->getASTContext();
   ASSERT(loc.isValid());
-  return new (ctx) TypeValueExpr(loc, paramDecl);
+  auto repr = UnqualifiedIdentTypeRepr::create(ctx, loc, decl->createNameRef());
+  repr->setValue(decl, dc);
+  return new (ctx) TypeValueExpr(repr);
+}
+
+GenericTypeParamDecl *TypeValueExpr::getParamDecl() const {
+  auto declRefRepr = cast<DeclRefTypeRepr>(getRepr());
+  return cast<GenericTypeParamDecl>(declRefRepr->getBoundDecl());
+}
+
+SourceRange TypeValueExpr::getSourceRange() const {
+  return getRepr()->getSourceRange();
 }
 
 ExistentialArchetypeType *OpenExistentialExpr::getOpenedArchetype() const {

lib/AST/FeatureSet.cpp

@@ -12,6 +12,7 @@
 
 #include "FeatureSet.h"
 
+#include "swift/AST/ASTWalker.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/ExistentialLayout.h"
 #include "swift/AST/GenericParamList.h"
@@ -470,6 +471,54 @@ static bool usesFeatureValueGenerics(Decl *decl) {
   return false;
 }
 
+class UsesTypeValueExpr : public ASTWalker {
+public:
+  bool used = false;
+
+  PreWalkResult<Expr *> walkToExprPre(Expr *expr) override {
+    if (isa<TypeValueExpr>(expr)) {
+      used = true;
+      return Action::Stop();
+    }
+
+    return Action::Continue(expr);
+  }
+};
+
+static bool usesFeatureValueGenericsNameLookup(Decl *decl) {
+  // Be conservative and mark any function that has a TypeValueExpr in its body
+  // as having used this feature. It's a little difficult to fine grain this
+  // check because the following:
+  //
+  // func a() -> Int {
+  //   A<123>.n
+  // }
+  //
+  // Would appear to have the same expression as something like:
+  //
+  // extension A where n == 123 {
+  //   func b() -> Int {
+  //     n
+  //   }
+  // }
+
+  auto fn = dyn_cast<AbstractFunctionDecl>(decl);
+
+  if (!fn)
+    return false;
+
+  auto body = fn->getMacroExpandedBody();
+
+  if (!body)
+    return false;
+
+  UsesTypeValueExpr utve;
+
+  body->walk(utve);
+
+  return utve.used;
+}
+
 static bool usesFeatureCoroutineAccessors(Decl *decl) {
   auto accessorDeclUsesFeatureCoroutineAccessors = [](AccessorDecl *accessor) {
     return requiresFeatureCoroutineAccessors(accessor->getAccessorKind());

lib/AST/NameLookup.cpp

@@ -2739,6 +2739,18 @@ QualifiedLookupRequest::evaluate(Evaluator &eval, const DeclContext *DC,
       }
     }
 
+    // Qualified name lookup can find generic value parameters.
+    auto gpList = current->getGenericParams();
+
+    // .. But not in type contexts (yet)
+    if (!(options & NL_OnlyTypes) && gpList && !member.isSpecial()) {
+      auto gp = gpList->lookUpGenericParam(member.getBaseIdentifier());
+
+      if (gp && gp->isValue()) {
+        decls.push_back(gp);
+      }
+    }
+
     // If we're not looking at a protocol and we're not supposed to
     // visit the protocols that this type conforms to, skip the next
     // step.

lib/Sema/CSApply.cpp

@@ -1631,6 +1631,29 @@ namespace {
       // Build a member reference.
       auto memberRef = resolveConcreteDeclRef(member, memberLocator);
 
+      // If our member reference is a value generic, then the resulting
+      // expression is the type value one to access the underlying parameter's
+      // value.
+      //
+      // This can occur in code that does something like: 'type(of: x).a' where
+      // 'a' is the static value generic member.
+      if (auto gp = dyn_cast<GenericTypeParamDecl>(member)) {
+        if (gp->isValue()) {
+          auto refType = adjustedOpenedType;
+          auto ref = TypeValueExpr::createForDecl(memberLoc, gp, dc);
+          cs.setType(ref, refType);
+
+          auto gpTy = gp->getDeclaredInterfaceType();
+          auto subs = baseTy->getContextSubstitutionMap();
+          ref->setParamType(gpTy.subst(subs));
+
+          auto result = new (ctx) DotSyntaxBaseIgnoredExpr(base, dotLoc, ref,
+                                                           refType);
+          cs.setType(result, refType);
+          return result;
+        }
+      }
+
       // If we're referring to a member type, it's just a type
       // reference.
       if (auto *TD = dyn_cast<TypeDecl>(member)) {
@@ -3222,8 +3245,20 @@ namespace {
 
     Expr *visitTypeValueExpr(TypeValueExpr *expr) {
       auto toType = simplifyType(cs.getType(expr));
-      assert(toType->isEqual(expr->getParamDecl()->getValueType()));
+      ASSERT(toType->isEqual(expr->getParamDecl()->getValueType()));
       cs.setType(expr, toType);
+
+      auto declRefRepr = cast<DeclRefTypeRepr>(expr->getRepr());
+      auto resolvedTy =
+          TypeResolution::resolveContextualType(declRefRepr, cs.DC,
+                                             TypeResolverContext::InExpression,
+                                                nullptr, nullptr, nullptr);
+
+      if (!resolvedTy || resolvedTy->hasError())
+        return nullptr;
+
+      expr->setParamType(resolvedTy);
+
       return expr;
     }
 

lib/Sema/CSGen.cpp

@@ -1723,9 +1723,6 @@ namespace {
     }
 
     Type visitTypeValueExpr(TypeValueExpr *E) {
-      auto ty = E->getParamDecl()->getDeclaredInterfaceType();
-      auto paramType = CS.DC->mapTypeIntoContext(ty);
-      E->setParamType(paramType);
       return E->getParamDecl()->getValueType();
     }
 

lib/Sema/PreCheckTarget.cpp

@@ -817,8 +817,7 @@ Expr *TypeChecker::resolveDeclRefExpr(UnresolvedDeclRefExpr *UDRE,
                    : D->getInterfaceType());
     } else {
       if (makeTypeValue) {
-        return TypeValueExpr::createForDecl(UDRE->getNameLoc(),
-                                            cast<GenericTypeParamDecl>(D));
+        return TypeValueExpr::createForDecl(UDRE->getNameLoc(), D, LookupDC);
       } else {
         return TypeExpr::createForDecl(UDRE->getNameLoc(), D, LookupDC);
       }
@@ -1853,7 +1852,7 @@ TypeExpr *PreCheckTarget::simplifyUnresolvedSpecializeExpr(
     UnresolvedSpecializeExpr *us) {
   // If this is a reference type a specialized type, form a TypeExpr.
   // The base should be a TypeExpr that we already resolved.
-  if (auto *te = dyn_cast<TypeExpr>(us->getSubExpr())) {
+  if (auto *te = dyn_cast_or_null<TypeExpr>(us->getSubExpr())) {
     if (auto *declRefTR =
             dyn_cast_or_null<DeclRefTypeRepr>(te->getTypeRepr())) {
       return TypeExpr::createForSpecializedDecl(

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -728,6 +728,20 @@ CheckRedeclarationRequest::evaluate(Evaluator &eval, ValueDecl *current,
       auto found = nominal->lookupDirect(current->getBaseName(), SourceLoc(),
                                          flags);
       otherDefinitions.append(found.begin(), found.end());
+
+      // Look into the generics of the type. Value generic parameters can appear
+      // as static members of the type.
+      if (auto genericDC = static_cast<Decl *>(nominal)->getAsGenericContext()) {
+        auto gpList = genericDC->getGenericParams();
+
+        if (gpList && !current->getBaseName().isSpecial()) {
+          auto gp = gpList->lookUpGenericParam(current->getBaseIdentifier());
+
+          if (gp && gp->isValue()) {
+            otherDefinitions.push_back(gp);
+          }
+        }
+      }
     }
   } else if (currentDC->isLocalContext()) {
     if (!current->isImplicit()) {
@@ -1135,6 +1149,7 @@ CheckRedeclarationRequest::evaluate(Evaluator &eval, ValueDecl *current,
       break;
     }
   }
+
   return std::make_tuple<>();
 }
 

lib/Sema/TypeCheckType.cpp

@@ -6335,6 +6335,18 @@ Type TypeChecker::substMemberTypeWithBase(TypeDecl *member,
     resultType = TypeAliasType::get(aliasDecl, sugaredBaseTy, {}, resultType);
   }
 
+  // However, if overload resolution finds a value generic decl from name
+  // lookup, replace the returned member type to be the underlying value type
+  // of the generic.
+  //
+  // This can occur in code that does something like: 'type(of: x).a' where
+  // 'a' is the static value generic member.
+  if (auto gp = dyn_cast<GenericTypeParamDecl>(member)) {
+    if (gp->isValue()) {
+      resultType = gp->getValueType();
+    }
+  }
+
   return resultType;
 }
 

lib/Sema/TypeOfReference.cpp

@@ -1557,6 +1557,13 @@ DeclReferenceType ConstraintSystem::getTypeOfMemberReference(
     // Wrap it in a metatype.
     memberTy = MetatypeType::get(memberTy);
 
+    // If this is a value generic, undo the wrapping. 'substMemberTypeWithBase'
+    // returns the underlying value type of the value generic (e.g. 'Int').
+    if (isa<GenericTypeParamDecl>(value) &&
+        cast<GenericTypeParamDecl>(value)->isValue()) {
+      memberTy = memberTy->castTo<MetatypeType>()->getInstanceType();
+    }
+
     auto openedType = FunctionType::get({baseObjParam}, memberTy);
     return { openedType, openedType, memberTy, memberTy, Type() };
   }

stdlib/public/core/InlineArray.swift

@@ -272,14 +272,6 @@ extension InlineArray where Element: ~Copyable {
   @available(SwiftStdlib 6.2, *)
   public typealias Index = Int
 
-  // FIXME: Remove when SE-0452 "Integer Generic Parameters" is implemented.
-  @available(SwiftStdlib 6.2, *)
-  @_alwaysEmitIntoClient
-  @_transparent
-  public static var count: Int {
-    count
-  }
-
   /// The number of elements in the array.
   ///
   /// - Complexity: O(1)

test/ModuleInterface/value_generics.swift

@@ -14,6 +14,8 @@ public struct Slab<Element, let N: Int> {
   public var count: Int {
     N
   }
+
+  public init() {}
 }
 
 // CHECK: public func usesGenericSlab<let N : Swift.Int>(_: ValueGeneric.Slab<Swift.Int, N>)
@@ -24,3 +26,27 @@ public func usesConcreteSlab(_: Slab<Int, 2>) {}
 
 // CHECK: public func usesNegativeSlab(_: ValueGeneric.Slab<Swift.String, -10>)
 public func usesNegativeSlab(_: Slab<String, -10>) {}
+
+// CHECK: $ValueGenericsNameLookup
+@inlinable
+public func test() -> Int {
+  // CHECK: Slab<Int, 123>.N
+  Slab<Int, 123>.N
+}
+
+// CHECK: $ValueGenericsNameLookup
+@inlinable
+public func test2() -> Int {
+  // CHECK: type(of: Slab<Int, 123>()).N
+  type(of: Slab<Int, 123>()).N
+}
+
+// CHECK: $ValueGenericsNameLookup
+@inlinable
+public func test3() {
+  {
+    print(123)
+    print(123)
+    print(Slab<Int, 123>.N)
+  }()
+}