Suggest narrowing an existing availability context, when feasible.

include/swift/AST/Attr.h

@@ -589,15 +589,18 @@ class AvailableAttr : public DeclAttribute {
                    PlatformKind Platform,
                    StringRef Message, StringRef Rename,
                    const clang::VersionTuple &Introduced,
+                   SourceRange IntroducedRange,
                    const clang::VersionTuple &Deprecated,
+                   SourceRange DeprecatedRange,
                    const clang::VersionTuple &Obsoleted,
+                   SourceRange ObsoletedRange,
                    PlatformAgnosticAvailabilityKind PlatformAgnostic,
                    bool Implicit)
     : DeclAttribute(DAK_Available, AtLoc, Range, Implicit),
       Message(Message), Rename(Rename),
-      INIT_VER_TUPLE(Introduced),
-      INIT_VER_TUPLE(Deprecated),
-      INIT_VER_TUPLE(Obsoleted),
+      INIT_VER_TUPLE(Introduced), IntroducedRange(IntroducedRange),
+      INIT_VER_TUPLE(Deprecated), DeprecatedRange(DeprecatedRange),
+      INIT_VER_TUPLE(Obsoleted), ObsoletedRange(ObsoletedRange),
       PlatformAgnostic(PlatformAgnostic),
       Platform(Platform)
   {}
@@ -618,12 +621,21 @@ class AvailableAttr : public DeclAttribute {
   /// Indicates when the symbol was introduced.
   const Optional<clang::VersionTuple> Introduced;
 
+  /// Indicates where the Introduced version was specified.
+  const SourceRange IntroducedRange;
+
   /// Indicates when the symbol was deprecated.
   const Optional<clang::VersionTuple> Deprecated;
 
+  /// Indicates where the Deprecated version was specified.
+  const SourceRange DeprecatedRange;
+
   /// Indicates when the symbol was obsoleted.
   const Optional<clang::VersionTuple> Obsoleted;
 
+  /// Indicates where the Obsoleted version was specified.
+  const SourceRange ObsoletedRange;
+
   /// Indicates if the declaration has platform-agnostic availability.
   const PlatformAgnosticAvailabilityKind PlatformAgnostic;
 

include/swift/AST/TypeRefinementContext.h

@@ -225,7 +225,16 @@ class TypeRefinementContext {
   /// or an invalid location if the context reflects the minimum deployment
   // target.
   SourceLoc getIntroductionLoc() const;
-
+
+  /// Returns the source range covering a _single_ decl-attribute or statement
+  /// condition that introduced the refinement context for a given platform
+  /// version; if zero or multiple such responsible attributes or statements
+  /// exist, returns an invalid SourceRange.
+  SourceRange
+  getAvailabilityConditionVersionSourceRange(
+      PlatformKind Platform,
+      const clang::VersionTuple &Version) const;
+
   /// Returns the source range on which this context refines types.
   SourceRange getSourceRange() const { return SrcRange; }
 

lib/AST/Attr.cpp

@@ -715,7 +715,10 @@ AvailableAttr::createPlatformAgnostic(ASTContext &C,
   }
   return new (C) AvailableAttr(
     SourceLoc(), SourceRange(), PlatformKind::none, Message, Rename,
-    NoVersion, NoVersion, Obsoleted, Kind, /* isImplicit */ false);
+    NoVersion, SourceRange(),
+    NoVersion, SourceRange(),
+    Obsoleted, SourceRange(),
+    Kind, /* isImplicit */ false);
 }
 
 bool AvailableAttr::isActivePlatform(const ASTContext &ctx) const {

lib/AST/Availability.cpp

@@ -91,7 +91,10 @@ createAvailableAttr(PlatformKind Platform,
   return new (Context) AvailableAttr(
       SourceLoc(), SourceRange(), Platform,
       /*Message=*/StringRef(),
-      /*Rename=*/StringRef(), Introduced, Deprecated, Obsoleted,
+      /*Rename=*/StringRef(),
+        Introduced, /*IntroducedRange=*/SourceRange(),
+        Deprecated, /*DeprecatedRange=*/SourceRange(),
+        Obsoleted, /*ObsoletedRange=*/SourceRange(),
       Inferred.PlatformAgnostic, /*Implicit=*/true);
 }
 

lib/AST/TypeRefinementContext.cpp

@@ -194,6 +194,99 @@ SourceLoc TypeRefinementContext::getIntroductionLoc() const {
   llvm_unreachable("Unhandled Reason in switch.");
 }
 
+static SourceRange
+getAvailabilityConditionVersionSourceRange(const PoundAvailableInfo *PAI,
+                                           PlatformKind Platform,
+                                           const clang::VersionTuple &Version) {
+  SourceRange Range;
+  for (auto *S : PAI->getQueries()) {
+    if (auto *V = dyn_cast<PlatformVersionConstraintAvailabilitySpec>(S)) {
+      if (V->getPlatform() == Platform && V->getVersion() == Version) {
+        // More than one: return invalid range, no unique choice.
+        if (Range.isValid())
+          return SourceRange();
+        else
+          Range = V->getVersionSrcRange();
+      }
+    }
+  }
+  return Range;
+}
+
+static SourceRange
+getAvailabilityConditionVersionSourceRange(
+    const MutableArrayRef<StmtConditionElement> &Conds,
+    PlatformKind Platform,
+    const clang::VersionTuple &Version) {
+  SourceRange Range;
+  for (auto const& C : Conds) {
+    if (C.getKind() == StmtConditionElement::CK_Availability) {
+      SourceRange R = getAvailabilityConditionVersionSourceRange(
+        C.getAvailability(), Platform, Version);
+      // More than one: return invalid range.
+      if (Range.isValid())
+        return SourceRange();
+      else
+        Range = R;
+    }
+  }
+  return Range;
+}
+
+static SourceRange
+getAvailabilityConditionVersionSourceRange(const DeclAttributes &DeclAttrs,
+                                           PlatformKind Platform,
+                                           const clang::VersionTuple &Version) {
+  SourceRange Range;
+  for (auto *Attr : DeclAttrs) {
+    if (auto *AA = dyn_cast<AvailableAttr>(Attr)) {
+      if (AA->Introduced.hasValue() &&
+          AA->Introduced.getValue() == Version &&
+          AA->Platform == Platform) {
+
+        // More than one: return invalid range.
+        if (Range.isValid())
+          return SourceRange();
+        else
+          Range = AA->IntroducedRange;
+      }
+    }
+  }
+  return Range;
+}
+
+SourceRange
+TypeRefinementContext::getAvailabilityConditionVersionSourceRange(
+    PlatformKind Platform,
+    const clang::VersionTuple &Version) const {
+  switch (getReason()) {
+  case Reason::Decl:
+    return ::getAvailabilityConditionVersionSourceRange(
+      Node.getAsDecl()->getAttrs(), Platform, Version);
+
+  case Reason::IfStmtThenBranch:
+  case Reason::IfStmtElseBranch:
+    return ::getAvailabilityConditionVersionSourceRange(
+      Node.getAsIfStmt()->getCond(), Platform, Version);
+
+  case Reason::ConditionFollowingAvailabilityQuery:
+    return ::getAvailabilityConditionVersionSourceRange(
+      Node.getAsPoundAvailableInfo(), Platform, Version);
+
+  case Reason::GuardStmtFallthrough:
+  case Reason::GuardStmtElseBranch:
+    return ::getAvailabilityConditionVersionSourceRange(
+      Node.getAsGuardStmt()->getCond(), Platform, Version);
+
+  case Reason::WhileStmtBody:
+    return ::getAvailabilityConditionVersionSourceRange(
+      Node.getAsWhileStmt()->getCond(), Platform, Version);
+
+  case Reason::Root:
+    return SourceRange();
+  }
+}
+
 void TypeRefinementContext::print(raw_ostream &OS, SourceManager &SrcMgr,
                                   unsigned Indent) const {
   OS.indent(Indent);

lib/ClangImporter/ImportDecl.cpp

@@ -1556,8 +1556,11 @@ static void applyAvailableAttribute(Decl *decl, AvailabilityContext &info,
                                       /*Message=*/StringRef(),
                                       /*Rename=*/StringRef(),
                                       info.getOSVersion().getLowerEndpoint(),
+                                      /*IntroducedRange*/SourceRange(),
                                       /*Deprecated=*/noVersion,
+                                      /*DeprecatedRange*/SourceRange(),
                                       /*Obsoleted=*/noVersion,
+                                      /*ObsoletedRange*/SourceRange(),
                                       PlatformAgnosticAvailabilityKind::None,
                                       /*Implicit=*/false);
 
@@ -6571,7 +6574,12 @@ void ClangImporter::Implementation::importAttributes(
       auto AvAttr = new (C) AvailableAttr(SourceLoc(), SourceRange(),
                                           platformK.getValue(),
                                           message, swiftReplacement,
-                                          introduced, deprecated, obsoleted,
+                                          introduced,
+                                          /*IntroducedRange=*/SourceRange(),
+                                          deprecated,
+                                          /*DeprecatedRange=*/SourceRange(),
+                                          obsoleted,
+                                          /*ObsoletedRange=*/SourceRange(),
                                           PlatformAgnostic, /*Implicit=*/false);
 
       MappedDecl->getAttrs().add(AvAttr);

lib/Parse/ParseDecl.cpp

@@ -897,18 +897,21 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
       for (auto *Spec : Specs) {
         PlatformKind Platform;
         clang::VersionTuple Version;
+        SourceRange VersionRange;
         PlatformAgnosticAvailabilityKind PlatformAgnostic;
 
         if (auto *PlatformVersionSpec =
             dyn_cast<PlatformVersionConstraintAvailabilitySpec>(Spec)) {
           Platform = PlatformVersionSpec->getPlatform();
           Version = PlatformVersionSpec->getVersion();
+          VersionRange = PlatformVersionSpec->getVersionSrcRange();
           PlatformAgnostic = PlatformAgnosticAvailabilityKind::None;
 
         } else if (auto *LanguageVersionSpec =
                    dyn_cast<LanguageVersionConstraintAvailabilitySpec>(Spec)) {
           Platform = PlatformKind::none;
           Version = LanguageVersionSpec->getVersion();
+          VersionRange = LanguageVersionSpec->getVersionSrcRange();
           PlatformAgnostic =
             PlatformAgnosticAvailabilityKind::SwiftVersionSpecific;
 
@@ -922,8 +925,11 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
                                      /*Message=*/StringRef(),
                                      /*Rename=*/StringRef(),
                                      /*Introduced=*/Version,
+                                     /*IntroducedRange=*/VersionRange,
                                      /*Deprecated=*/clang::VersionTuple(),
+                                     /*DeprecatedRange=*/SourceRange(),
                                      /*Obsoleted=*/clang::VersionTuple(),
+                                     /*ObsoletedRange=*/SourceRange(),
                                      PlatformAgnostic,
                                      /*Implicit=*/true));
       }
@@ -941,6 +947,7 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
 
     StringRef Message, Renamed;
     clang::VersionTuple Introduced, Deprecated, Obsoleted;
+    SourceRange IntroducedRange, DeprecatedRange, ObsoletedRange;
     auto PlatformAgnostic = PlatformAgnosticAvailabilityKind::None;
     bool AnyAnnotations = false;
     int ParamIndex = 0;
@@ -1060,8 +1067,10 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
                            (ArgumentKind == IsDeprecated) ? Deprecated :
                                                             Obsoleted;
 
-        SourceRange VersionRange;
-
+        auto &VersionRange = (ArgumentKind == IsIntroduced) ? IntroducedRange :
+                             (ArgumentKind == IsDeprecated) ? DeprecatedRange :
+                                                              ObsoletedRange;
+
         if (parseVersionTuple(
                 VersionArg, VersionRange,
                 Diagnostic(diag::attr_availability_expected_version,
@@ -1127,9 +1136,9 @@ bool Parser::parseNewDeclAttribute(DeclAttributes &Attributes, SourceLoc AtLoc,
                        AvailableAttr(AtLoc, AttrRange,
                                         PlatformKind.getValue(),
                                         Message, Renamed,
-                                        Introduced,
-                                        Deprecated,
-                                        Obsoleted,
+                                        Introduced, IntroducedRange,
+                                        Deprecated, DeprecatedRange,
+                                        Obsoleted, ObsoletedRange,
                                         PlatformAgnostic,
                                         /*Implicit=*/false));
       } else {