[NFC] Simplify function type representation checks.

Author: varungandhi-apple

include/swift/AST/ExtInfo.h

@@ -169,6 +169,45 @@ enum class SILFunctionTypeRepresentation : uint8_t {
   Closure,
 };
 
+/// Returns true if the function with this convention doesn't carry a context.
+constexpr bool
+isThinRepresentation(FunctionTypeRepresentation rep) {
+  switch (rep) {
+    case FunctionTypeRepresentation::Swift:
+    case FunctionTypeRepresentation::Block:
+      return false;
+    case FunctionTypeRepresentation::Thin:
+    case FunctionTypeRepresentation::CFunctionPointer:
+      return true;
+  }
+  llvm_unreachable("Unhandled FunctionTypeRepresentation in switch.");
+}
+
+/// Returns true if the function with this convention doesn't carry a context.
+constexpr bool
+isThinRepresentation(SILFunctionTypeRepresentation rep) {
+  switch (rep) {
+  case SILFunctionTypeRepresentation::Thick:
+  case SILFunctionTypeRepresentation::Block:
+    return false;
+  case SILFunctionTypeRepresentation::Thin:
+  case SILFunctionTypeRepresentation::Method:
+  case SILFunctionTypeRepresentation::ObjCMethod:
+  case SILFunctionTypeRepresentation::WitnessMethod:
+  case SILFunctionTypeRepresentation::CFunctionPointer:
+  case SILFunctionTypeRepresentation::Closure:
+    return true;
+  }
+  llvm_unreachable("Unhandled SILFunctionTypeRepresentation in switch.");
+}
+
+/// Returns true if the function with this convention carries a context.
+template <typename Repr>
+constexpr bool
+isThickRepresentation(Repr repr) {
+  return !isThinRepresentation(repr);
+}
+
 constexpr SILFunctionTypeRepresentation
 convertRepresentation(FunctionTypeRepresentation rep) {
   switch (rep) {
@@ -350,19 +389,7 @@ class ASTExtInfoBuilder {
 
   /// True if the function representation carries context.
   constexpr bool hasContext() const {
-    switch (getSILRepresentation()) {
-    case SILFunctionTypeRepresentation::Thick:
-    case SILFunctionTypeRepresentation::Block:
-      return true;
-    case SILFunctionTypeRepresentation::Thin:
-    case SILFunctionTypeRepresentation::Method:
-    case SILFunctionTypeRepresentation::ObjCMethod:
-    case SILFunctionTypeRepresentation::WitnessMethod:
-    case SILFunctionTypeRepresentation::CFunctionPointer:
-    case SILFunctionTypeRepresentation::Closure:
-      return false;
-    }
-    llvm_unreachable("Unhandled SILFunctionTypeRepresentation in switch.");
+    return isThickRepresentation(getSILRepresentation());
   }
 
   // Note that we don't have setters. That is by design, use

lib/Sema/CSSimplify.cpp

@@ -1552,22 +1552,9 @@ ConstraintSystem::matchTupleTypes(TupleType *tuple1, TupleType *tuple2,
 static bool
 isSubtypeOf(FunctionTypeRepresentation potentialSubRepr,
             FunctionTypeRepresentation potentialSuperRepr) {
-  auto isThin = [](FunctionTypeRepresentation rep) {
-    return rep == FunctionTypeRepresentation::CFunctionPointer ||
-        rep == FunctionTypeRepresentation::Thin;
-  };
-  
-  // Allowing "thin" (c, thin) to "thin" conversions
-  if (isThin(potentialSubRepr) && isThin(potentialSuperRepr))
-    return true;
-  
-  // Allowing all to "thick" (swift, block) conversions
-  // "thin" (c, thin) to "thick" or "thick" to "thick"
-  if (potentialSuperRepr == FunctionTypeRepresentation::Swift ||
-      potentialSuperRepr == FunctionTypeRepresentation::Block)
-    return true;
-  
-  return potentialSubRepr == potentialSuperRepr;
+  return (potentialSubRepr == potentialSuperRepr)
+       || isThinRepresentation(potentialSubRepr)
+       || isThickRepresentation(potentialSuperRepr);
 }
 
 /// Returns true if `constraint rep1 rep2` is satisfied.