[CS] NFC: Default the allowFreeTypeVariables parameter

All but one client wants to set this to anything
other than `FreeTypeVariableBinding::Disallow`.

Author: hamishknight

include/swift/Sema/ConstraintSystem.h

@@ -5110,7 +5110,8 @@ class ConstraintSystem {
   /// \returns true if an error occurred, false otherwise.
   LLVM_NODISCARD
   bool generateConstraints(SolutionApplicationTarget &target,
-                           FreeTypeVariableBinding allowFreeTypeVariables);
+                           FreeTypeVariableBinding allowFreeTypeVariables =
+                               FreeTypeVariableBinding::Disallow);
 
   /// Generate constraints for the body of the given function or closure.
   ///

lib/Sema/BuilderTransform.cpp

@@ -359,7 +359,7 @@ class BuilderClosureVisitor
     // binding.
     if (cs) {
       SolutionApplicationTarget target(patternBinding);
-      if (cs->generateConstraints(target, FreeTypeVariableBinding::Disallow))
+      if (cs->generateConstraints(target))
         hadError = true;
     }
   }
@@ -661,7 +661,7 @@ class BuilderClosureVisitor
       // FIXME: Add contextual type purpose for switch subjects?
       SolutionApplicationTarget target(subjectExpr, dc, CTP_Unused, Type(),
                                        /*isDiscarded=*/false);
-      if (cs->generateConstraints(target, FreeTypeVariableBinding::Disallow)) {
+      if (cs->generateConstraints(target)) {
         hadError = true;
         return nullptr;
       }
@@ -789,7 +789,7 @@ class BuilderClosureVisitor
     auto target = SolutionApplicationTarget::forForEachStmt(
         forEachStmt, dc, /*bindPatternVarsOneWay=*/true);
     if (cs) {
-      if (cs->generateConstraints(target, FreeTypeVariableBinding::Disallow)) {
+      if (cs->generateConstraints(target)) {
         hadError = true;
         return nullptr;
       }
@@ -890,7 +890,7 @@ class BuilderClosureVisitor
                                        CTP_ThrowStmt,
                                        ctx.getErrorExistentialType(),
                                        /*isDiscarded=*/false);
-      if (cs->generateConstraints(target, FreeTypeVariableBinding::Disallow))
+      if (cs->generateConstraints(target))
         hadError = true;
 
       cs->setSolutionApplicationTarget(throwStmt, target);

lib/Sema/CSGen.cpp

@@ -4074,7 +4074,7 @@ namespace {
         auto &CS = CG.getConstraintSystem();
         for (const auto &capture : captureList->getCaptureList()) {
           SolutionApplicationTarget target(capture.PBD);
-          if (CS.generateConstraints(target, FreeTypeVariableBinding::Disallow))
+          if (CS.generateConstraints(target))
             return Action::Stop();
         }
       }
@@ -4327,8 +4327,7 @@ generateForEachStmtConstraints(
         TypeLoc::withoutLoc(sequenceProto->getDeclaredInterfaceType()),
         CTP_ForEachSequence);
 
-    if (cs.generateConstraints(makeIteratorTarget,
-                               FreeTypeVariableBinding::Disallow))
+    if (cs.generateConstraints(makeIteratorTarget))
       return None;
 
     forEachStmtInfo.makeIteratorVar = PB;
@@ -4613,7 +4612,7 @@ bool ConstraintSystem::generateConstraints(
                          : SolutionApplicationTarget::forUninitializedVar(
                                patternBinding, index, patternType);
 
-      if (generateConstraints(target, FreeTypeVariableBinding::Disallow)) {
+      if (generateConstraints(target)) {
         hadError = true;
         continue;
       }
@@ -4698,7 +4697,7 @@ bool ConstraintSystem::generateConstraints(StmtCondition condition,
       auto target = SolutionApplicationTarget(symbolExpr, dc, CTP_Unused,
                                               Type(), /*isDiscarded=*/false);
 
-      if (generateConstraints(target, FreeTypeVariableBinding::Disallow))
+      if (generateConstraints(target))
         return true;
 
       setSolutionApplicationTarget(&condElement, target);

lib/Sema/CSSimplify.cpp

@@ -9869,7 +9869,7 @@ static bool inferEnumMemberThroughTildeEqualsOperator(
     }
   }
 
-  if (cs.generateConstraints(target, FreeTypeVariableBinding::Disallow))
+  if (cs.generateConstraints(target))
     return true;
 
   // Sub-expression associated with expression pattern is the enum element

lib/Sema/CSSolver.cpp

@@ -1684,7 +1684,7 @@ bool ConstraintSystem::solveForCodeCompletion(
         << "--- Code Completion ---\n";
   }
 
-  if (generateConstraints(target, FreeTypeVariableBinding::Disallow))
+  if (generateConstraints(target))
     return false;
 
   solveForCodeCompletion(solutions);

lib/Sema/CSSyntacticElement.cpp

@@ -580,7 +580,7 @@ class SyntacticElementConstraintGenerator
         forEachStmt, context.getAsDeclContext(),
         /*bindTypeVarsOneWay=*/false);
 
-    if (cs.generateConstraints(target, FreeTypeVariableBinding::Disallow)) {
+    if (cs.generateConstraints(target)) {
       hadError = true;
       return;
     }
@@ -734,7 +734,7 @@ class SyntacticElementConstraintGenerator
     if (isPlaceholderVar(patternBinding))
       return;
 
-    if (cs.generateConstraints(*target, FreeTypeVariableBinding::Disallow)) {
+    if (cs.generateConstraints(*target)) {
       hadError = true;
       return;
     }
@@ -1128,7 +1128,7 @@ class SyntacticElementConstraintGenerator
                                      contextualResultInfo.getType(),
                                      /*isDiscarded=*/false);
 
-    if (cs.generateConstraints(target, FreeTypeVariableBinding::Disallow)) {
+    if (cs.generateConstraints(target)) {
       hadError = true;
       return;
     }
@@ -1430,7 +1430,7 @@ ConstraintSystem::simplifySyntacticElementConstraint(
                                      contextInfo.purpose, contextInfo.getType(),
                                      contextualTypeLoc, isDiscarded);
 
-    if (generateConstraints(target, FreeTypeVariableBinding::Disallow))
+    if (generateConstraints(target))
       return SolutionKind::Error;
 
     setSolutionApplicationTarget(expr, target);