[DNM][stdlib] Add exponentiation precedence group and operator declaration

include/swift/AST/Attr.def

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -630,6 +630,11 @@ DECL_ATTR(hasAsyncAlternative, HasAsyncAlternative,
   APIStableToAdd | APIStableToRemove,
   111)
 
+SIMPLE_DECL_ATTR(apex, Apex,
+  OnPrecedenceGroup |
+  ABIStableToAdd | ABIStableToRemove | APIBreakingToAdd | APIBreakingToRemove,
+  112)
+
 #undef TYPE_ATTR
 #undef DECL_ATTR_ALIAS
 #undef CONTEXTUAL_DECL_ATTR_ALIAS

include/swift/AST/Decl.h

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -6995,6 +6995,10 @@ class PrecedenceGroupDecl : public Decl {
     return { getLowerThanBuffer(), NumLowerThan };
   }
 
+  bool isApex() const {
+    return getAttrs().hasAttribute<ApexAttr>();
+  }
+
   static bool classof(const Decl *D) {
     return D->getKind() == DeclKind::PrecedenceGroup;
   }

include/swift/AST/DiagnosticsSema.def

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -976,6 +976,9 @@ NOTE(previous_precedence_group_decl,none,
      "previous precedence group declaration here", ())
 NOTE(circular_reference_through_precedence_group, none,
      "through reference to precedence group %0 here", (Identifier))
+ERROR(precedence_group_higher_than_apex,none,
+      "precedence group cannot be given higher precedence than '@apex' group",
+      ())
 
 //------------------------------------------------------------------------------
 // MARK: Expression Type Checking Errors
@@ -3381,7 +3384,11 @@ ERROR(construct_protocol_by_name,none,
 
 // Operators
 ERROR(unknown_binop,none,
-       "operator is not a known binary operator", ())
+      "operator is not a known binary operator", ())
+ERROR(unordered_adjacent_unary_operator,none,
+      "operator in precedence group %0 and adjacent unary operator have "
+      "undefined relative precedence; use grouping parentheses",
+      (Identifier))
 ERROR(non_associative_adjacent_operators,none,
       "adjacent operators are in non-associative precedence group %0",
       (Identifier))

lib/Sema/TypeCheckAttr.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -99,6 +99,7 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
 
 #define IGNORED_ATTR(X) void visit##X##Attr(X##Attr *) {}
   IGNORED_ATTR(AlwaysEmitIntoClient)
+  IGNORED_ATTR(Apex)
   IGNORED_ATTR(HasInitialValue)
   IGNORED_ATTR(ClangImporterSynthesizedType)
   IGNORED_ATTR(Convenience)

lib/Sema/TypeCheckDecl.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -1450,8 +1450,19 @@ void swift::validatePrecedenceGroup(PrecedenceGroupDecl *PGD) {
       continue;
 
     // TODO: Requestify the lookup of a relation's group.
-    rel.Group = lookupPrecedenceGroupForRelation(
+    auto *group = lookupPrecedenceGroupForRelation(
         dc, rel, PrecedenceGroupDescriptor::HigherThan);
+    rel.Group = group;
+
+    if (group && group->isApex()) {
+      if (!PGD->isInvalid()) {
+        Diags.diagnose(rel.NameLoc, diag::precedence_group_higher_than_apex);
+        Diags.diagnose(group->getNameLoc(), diag::kind_declared_here,
+                       DescriptiveDeclKind::PrecedenceGroup);
+      }
+      PGD->setInvalid();
+    }
+
     if (rel.Group) {
       addedHigherThan = true;
     } else {
@@ -1474,6 +1485,13 @@ void swift::validatePrecedenceGroup(PrecedenceGroupDecl *PGD) {
     if (!group)
       group = dc->lookupPrecedenceGroup(rel.Name).getSingle();
 
+    if (group && PGD->isApex()) {
+      if (!PGD->isInvalid()) {
+        Diags.diagnose(rel.NameLoc, diag::precedence_group_higher_than_apex);
+      }
+      PGD->setInvalid();
+    }
+
     if (group &&
         group->getDeclContext()->getParentModule() == dc->getParentModule()) {
       if (!PGD->isInvalid()) {

lib/Sema/TypeCheckDeclOverride.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -1541,6 +1541,8 @@ namespace  {
 
     UNINTERESTING_ATTR(AtReasync)
 
+    UNINTERESTING_ATTR(Apex)
+
 #undef UNINTERESTING_ATTR
 
     void visitAvailableAttr(AvailableAttr *attr) {

lib/Sema/TypeCheckExpr.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -281,7 +281,34 @@ static Expr *makeBinOp(ASTContext &Ctx, Expr *Op, Expr *LHS, Expr *RHS,
     await->setSubExpr(sub);
     return await;
   }
-
+
+  // Operators in apex precedence groups are unordered relative to prefix and
+  // postfix operators.
+  if (opPrecedence && opPrecedence->isApex()) {
+    if (auto *prefixUnary = dyn_cast<PrefixUnaryExpr>(LHS)) {
+      Ctx.Diags.diagnose(Op->getLoc(),
+                         diag::unordered_adjacent_unary_operator,
+                         opPrecedence->getName())
+      .highlight(prefixUnary->getFn()->getSourceRange());
+    }
+    // Prefix '-' (but not '+') is lexed as part of a number literal rather than
+    // as a standalone operator.
+    else if (auto *numberLiteral = dyn_cast<NumberLiteralExpr>(LHS)) {
+      if (numberLiteral->isNegative()) {
+        Ctx.Diags.diagnose(Op->getLoc(),
+                           diag::unordered_adjacent_unary_operator,
+                           opPrecedence->getName())
+        .highlight(numberLiteral->getMinusLoc());
+      }
+    }
+    if (auto *postfixUnary = dyn_cast<PostfixUnaryExpr>(RHS)) {
+      Ctx.Diags.diagnose(Op->getLoc(),
+                         diag::unordered_adjacent_unary_operator,
+                         opPrecedence->getName())
+      .highlight(postfixUnary->getFn()->getSourceRange());
+    }
+  }
+
   // If this is an assignment operator, and the left operand is an optional
   // evaluation, pull the operator into the chain.
   if (opPrecedence && opPrecedence->isAssignment()) {

stdlib/public/core/FloatingPointTypes.swift.gyb

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -1243,6 +1243,30 @@ extension ${Self} {
   }
 }
 
+//===----------------------------------------------------------------------===//
+// Placeholder Operators
+//===----------------------------------------------------------------------===//
+
+//  TODO: Remove these operators once protocol-based math functions are
+//  incorporated from Swift Numerics into the standard library.
+
+${Availability(bits)}
+extension ${Self} {
+  @_alwaysEmitIntoClient
+  @available(*, unavailable,
+    message: "Import C standard library or Foundation to use 'pow' instead")
+  public static func ** (_ lhs: Self, _ rhs: Self) -> Self {
+    fatalError()
+  }
+
+  @_alwaysEmitIntoClient
+  @available(*, unavailable,
+    message: "Import C standard library or Foundation to use 'pow' instead")
+  public static func **= (_ lhs: inout Self, _ rhs: Self) {
+    fatalError()
+  }
+}
+
 //===----------------------------------------------------------------------===//
 // Strideable Conformance
 //===----------------------------------------------------------------------===//
@@ -1346,10 +1370,6 @@ internal struct _${Self}AnyHashableBox: _AnyHashableBox {
 ${Availability(bits)}
 extension ${Self} : ConcurrentValue { }
 
-//===----------------------------------------------------------------------===//
-// Deprecated operators
-//===----------------------------------------------------------------------===//
-
 % if bits in [16,80]:
 #else
 
@@ -1374,6 +1394,10 @@ public struct ${Self} {
 % end
 % end # for bits in all_floating_point_types
 
+//===----------------------------------------------------------------------===//
+// Deprecated Operators
+//===----------------------------------------------------------------------===//
+
 @_transparent
 @available(*, unavailable,
   message: "For floating point numbers use truncatingRemainder instead")

stdlib/public/core/Policy.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -368,7 +368,11 @@ precedencegroup MultiplicationPrecedence {
 precedencegroup BitwiseShiftPrecedence {
   higherThan: MultiplicationPrecedence
 }
-
+@apex
+precedencegroup ExponentiationPrecedence {
+  associativity: right
+  higherThan: MultiplicationPrecedence
+}
 
 //===----------------------------------------------------------------------===//
 // Standard operators
@@ -397,6 +401,7 @@ prefix operator ..<: Comparable
 // Standard infix operators.
 
 // "Exponentiative"
+infix operator  **: ExponentiationPrecedence
 
 infix operator  <<: BitwiseShiftPrecedence, BinaryInteger
 infix operator &<<: BitwiseShiftPrecedence, FixedWidthInteger
@@ -463,6 +468,7 @@ infix operator ||: LogicalDisjunctionPrecedence, Bool
 
 // Compound
 
+infix operator  **=: AssignmentPrecedence
 infix operator   *=: AssignmentPrecedence, Numeric
 infix operator  &*=: AssignmentPrecedence, FixedWidthInteger
 infix operator   /=: AssignmentPrecedence, BinaryInteger

test/IDE/complete_decl_attribute.swift

@@ -255,6 +255,7 @@ struct _S {
 // ON_MEMBER_LAST-DAG: Keyword/None:                       transpose[#Declaration Attribute#]; name=transpose
 // ON_MEMBER_LAST-DAG: Keyword/None:                       noDerivative[#Declaration Attribute#]; name=noDerivative
 // ON_MEMBER_LAST-DAG: Keyword/None:                       concurrent[#Declaration Attribute#]; name=concurrent
+// ON_MEMBER_LAST-DAG: Keyword/None:                       apex[#Declaration Attribute#]; name=apex
 // ON_MEMBER_LAST-NOT: Keyword
 // ON_MEMBER_LAST: Decl[Struct]/CurrModule:            MyStruct[#MyStruct#]; name=MyStruct
 // ON_MEMBER_LAST-NOT: Decl[PrecedenceGroup]
@@ -306,6 +307,7 @@ func dummy2() {}
 // KEYWORD_LAST-DAG: Keyword/None:                       transpose[#Declaration Attribute#]; name=transpose
 // KEYWORD_LAST-DAG: Keyword/None:                       noDerivative[#Declaration Attribute#]; name=noDerivative
 // KEYWORD_LAST-DAG: Keyword/None:                       concurrent[#Declaration Attribute#]; name=concurrent
+// KEYWORD_LAST-DAG: Keyword/None:                       apex[#Declaration Attribute#]; name=apex
 // KEYWORD_LAST-NOT: Keyword
 // KEYWORD_LAST: Decl[Struct]/CurrModule:            MyStruct[#MyStruct#]; name=MyStruct
 // KEYWORD_LAST:                  End completions