[ConstraintSystem] With designated types enabled, use fewer partitions.

In 119864a I moved the consideration
of top-level operators sooner when the designated types feature is
enabled, and that fixed some source compatibility issues that show up
in our test suite, but also introduced a new one.

For maximum source compatibility we'll just split the partitions up
into the operators from designated types, followed by operators that
are not deprecated or disabled, followed by the deprecated ones, and
finally the disabled ones.

Author: rudkx

lib/Sema/CSSolver.cpp

@@ -1723,6 +1723,10 @@ void ConstraintSystem::partitionForDesignatedTypes(
     auto *parentDC = funcDecl->getParent();
     auto *parentDecl = parentDC->getSelfNominalTypeDecl();
 
+    // Skip anything not defined in a nominal type.
+    if (!parentDecl)
+      return false;
+
     for (auto designatedTypeIndex : indices(designatedNominalTypes)) {
       auto *designatedNominal =
         designatedNominalTypes[designatedTypeIndex];
@@ -1807,7 +1811,6 @@ void ConstraintSystem::partitionDisjunction(
 
   SmallVector<unsigned, 4> disabled;
   SmallVector<unsigned, 4> unavailable;
-  SmallVector<unsigned, 4> globalScope;
 
   // First collect disabled constraints.
   forEachChoice(Choices, [&](unsigned index, Constraint *constraint) -> bool {
@@ -1831,20 +1834,6 @@ void ConstraintSystem::partitionDisjunction(
     });
   }
 
-  // Collect everything at the global scope.
-  forEachChoice(Choices, [&](unsigned index, Constraint *constraint) -> bool {
-    auto *decl = constraint->getOverloadChoice().getDecl();
-    auto *funcDecl = cast<FuncDecl>(decl);
-
-    // Skip anything defined within a type.
-    auto *parentDecl = funcDecl->getParent()->getAsDecl();
-    if (parentDecl)
-      return false;
-
-    globalScope.push_back(index);
-    return true;
-  });
-
   // Local function to create the next partition based on the options
   // passed in.
   PartitionAppendCallback appendPartition =
@@ -1857,9 +1846,6 @@ void ConstraintSystem::partitionDisjunction(
 
   partitionForDesignatedTypes(Choices, forEachChoice, appendPartition);
 
-  // Add all the things defined at global scope.
-  appendPartition(globalScope);
-
   SmallVector<unsigned, 4> everythingElse;
   // Gather the remaining options.
   forEachChoice(Choices, [&](unsigned index, Constraint *constraint) -> bool {