Merge pull request #33046 from DougGregor/function-builder-availability-cleanup

Author: swift-ci

include/swift/AST/DiagnosticsSema.def

@@ -5128,7 +5128,7 @@ NOTE(function_builder_infer_pick_specific, none,
      "apply function builder %0 (inferred from %select{protocol|dynamic replacement of}1 %2)",
      (Type, unsigned, DeclName))
 WARNING(function_builder_missing_limited_availability, none,
-        "function builder %0 does not implement `buildLimitedAvailability`; "
+        "function builder %0 does not implement 'buildLimitedAvailability'; "
         "this code may crash on earlier versions of the OS",
         (Type))
 

lib/Sema/BuilderTransform.cpp

@@ -515,7 +515,7 @@ class BuilderClosureVisitor
       return nullptr;
 
     // If there is a #available in the condition, the 'then' will need to
-    // be wrapped in a call to buildAvailabilityErasure(_:), if available.
+    // be wrapped in a call to buildLimitedAvailability(_:), if available.
     Expr *thenVarRefExpr = buildVarRef(
         thenVar, ifStmt->getThenStmt()->getEndLoc());
     if (findAvailabilityCondition(ifStmt->getCond()) &&
@@ -1202,10 +1202,14 @@ class BuilderClosureRewriter
     ifStmt->setThenStmt(newThen);
 
     // Look for a #available condition. If there is one, we need to check
-    // that the resulting type of the "then" does refer to any types that
+    // that the resulting type of the "then" doesn't refer to any types that
     // are unavailable in the enclosing context.
     //
-    // Note that this is for staging in support for
+    // Note that this is for staging in support for buildLimitedAvailability();
+    // the diagnostic is currently a warning, so that existing code that
+    // compiles today will continue to compile. Once function builder types
+    // have had the change to adopt buildLimitedAvailability(), we'll upgrade
+    // this warning to an error.
     if (auto availabilityCond = findAvailabilityCondition(ifStmt->getCond())) {
       SourceLoc loc = availabilityCond->getStartLoc();
       Type thenBodyType = solution.simplifyType(
@@ -1217,9 +1221,6 @@ class BuilderClosureRewriter
 
         if (auto reason = TypeChecker::checkDeclarationAvailability(
                               nominal, loc, dc)) {
-          // Note that the problem is with the function builder, not the body.
-          // This is for staging only. We want to disable #available in
-          // function builders that don't support this operation.
           ctx.Diags.diagnose(
               loc, diag::function_builder_missing_limited_availability,
               builderTransform.builderType);

test/Constraints/function_builder_availability.swift

@@ -65,7 +65,7 @@ tuplify(true) { cond in
   if #available(OSX 10.51, *) {
     globalFuncAvailableOn10_51()
     tuplify(false) { cond2 in
-      if cond, #available(OSX 10.52, *) { // expected-warning{{function builder 'TupleBuilder' does not implement `buildLimitedAvailability`; this code may crash on earlier versions of the OS}}
+      if cond, #available(OSX 10.52, *) { // expected-warning{{function builder 'TupleBuilder' does not implement 'buildLimitedAvailability'; this code may crash on earlier versions of the OS}}
         cond2
         globalFuncAvailableOn10_52()
       } else {