[Diagnostics] Replace curry level with a boolean flag

Since arbitrary currying is no longer allowed `level` could
be replaced with the boolean flag which identifies if curried
`self` should be skipped or not.

Author: xedin

lib/Sema/CalleeCandidateInfo.cpp

@@ -56,8 +56,8 @@ static bool isSubstitutableFor(Type type, ArchetypeType *archetype,
   return true;
 }
 
-UncurriedCandidate::UncurriedCandidate(ValueDecl *decl, unsigned level)
-: declOrExpr(decl), level(level), substituted(false) {
+UncurriedCandidate::UncurriedCandidate(ValueDecl *decl, bool skipCurriedSelf)
+: declOrExpr(decl), skipCurriedSelf(skipCurriedSelf), substituted(false) {
 
   if (auto *PD = dyn_cast<ParamDecl>(decl)) {
     if (PD->hasValidSignature())
@@ -95,15 +95,15 @@ ArrayRef<Identifier> UncurriedCandidate::getArgumentLabels(
   if (auto decl = getDecl()) {
     if (auto func = dyn_cast<AbstractFunctionDecl>(decl)) {
       if (func->hasImplicitSelfDecl()) {
-        if (level == 0) {
+        if (!skipCurriedSelf) {
           scratch.push_back(Identifier());
           return scratch;
         }
 
-        --level;
+        skipCurriedSelf = false;
       }
 
-      if (level == 0) {
+      if (!skipCurriedSelf) {
         // Retrieve the argument labels of the corresponding parameter list.
         for (auto param : *func->getParameters()) {
           scratch.push_back(param->getArgumentName());
@@ -112,20 +112,18 @@ ArrayRef<Identifier> UncurriedCandidate::getArgumentLabels(
       }
     } else if (auto enumElt = dyn_cast<EnumElementDecl>(decl)) {
       // 'self'
-      if (level == 0) {
+      if (!skipCurriedSelf) {
         scratch.push_back(Identifier());
         return scratch;
       }
 
       // The associated data of the case.
-      if (level == 1) {
-        auto *paramList = enumElt->getParameterList();
-        if (!paramList) return { };
-        for (auto param : *paramList) {
-          scratch.push_back(param->getArgumentName());
-        }
-        return scratch;
+      auto *paramList = enumElt->getParameterList();
+      if (!paramList) return { };
+      for (auto param : *paramList) {
+        scratch.push_back(param->getArgumentName());
       }
+      return scratch;
     }
   }
 
@@ -143,7 +141,8 @@ void UncurriedCandidate::dump() const {
     decl->dumpRef(llvm::errs());
   else
     llvm::errs() << "<<EXPR>>";
-  llvm::errs() << " - uncurry level " << level;
+  llvm::errs() << " - ignore curried self = " << (skipCurriedSelf ? "yes"
+                                                                  : "no");
 
   if (auto FT = getUncurriedFunctionType())
     llvm::errs() << " - type: " << Type(FT) << "\n";
@@ -322,7 +321,7 @@ CalleeCandidateInfo::evaluateCloseness(UncurriedCandidate candidate,
 
   auto candArgs = candidate.getParameters();
   SmallBitVector candDefaultMap =
-    computeDefaultMap(candArgs, candidate.getDecl(), candidate.level);
+    computeDefaultMap(candArgs, candidate.getDecl(), candidate.skipCurriedSelf);
 
   struct OurListener : public MatchCallArgumentListener {
     CandidateCloseness result = CC_ExactMatch;
@@ -589,28 +588,27 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
                                      /*implicitDotSyntax=*/false);
   }
 
-  // Determine the callee level for a "bare" reference to the given
-  // declaration.
-  auto getCalleeLevel = [implicitDotSyntax](ValueDecl *decl) -> unsigned {
+  // Determine if we need to skip "self" to get to a "bare" reference.
+  auto skipCurriedSelf = [implicitDotSyntax](ValueDecl *decl) -> bool {
     if (auto func = dyn_cast<FuncDecl>(decl)) {
       if (func->isOperator() && func->getDeclContext()->isTypeContext() &&
           !implicitDotSyntax)
-        return 1;
+        return true;
     }
 
-    return 0;
+    return false;
   };
 
   if (auto declRefExpr = dyn_cast<DeclRefExpr>(fn)) {
     auto decl = declRefExpr->getDecl();
-    candidates.push_back({ decl, getCalleeLevel(decl) });
+    candidates.push_back({ decl, skipCurriedSelf(decl) });
     declName = decl->getBaseName().userFacingName();
     return;
   }
 
   if (auto declRefExpr = dyn_cast<OtherConstructorDeclRefExpr>(fn)) {
     auto decl = declRefExpr->getDecl();
-    candidates.push_back({ decl, getCalleeLevel(decl) });
+    candidates.push_back({ decl, skipCurriedSelf(decl) });
 
     if (auto selfTy = decl->getDeclContext()->getSelfInterfaceType())
       declName = selfTy.getString() + ".init";
@@ -621,7 +619,7 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
 
   if (auto overloadedDRE = dyn_cast<OverloadedDeclRefExpr>(fn)) {
     for (auto cand : overloadedDRE->getDecls()) {
-      candidates.push_back({ cand, getCalleeLevel(cand) });
+      candidates.push_back({ cand, skipCurriedSelf(cand) });
     }
 
     if (!candidates.empty())
@@ -671,12 +669,13 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
         baseType = CS.getType(AE->getArg())->getWithoutSpecifierType();
 
       for (auto &C : candidates) {
-        C.level += 1;
+        bool hadCurriedSelf = C.skipCurriedSelf;
 
+        C.skipCurriedSelf = true;
         baseType = replaceTypeVariablesWithUnresolved(baseType);
 
         // Compute a new substituted type if we have a base type to apply.
-        if (baseType && C.level == 1 && C.getDecl()) {
+        if (baseType && !hadCurriedSelf && C.getDecl()) {
           baseType = baseType
             ->getWithoutSpecifierType()
             ->getMetatypeInstanceType();
@@ -691,7 +690,7 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
           }
         }
       }
-      
+
       return;
     }
   }
@@ -709,36 +708,35 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
 
   // Otherwise, we couldn't tell structurally what is going on here, so try to
   // dig something out of the constraint system.
-  unsigned uncurryLevel = 0;
+  bool hasCurriedSelf = false;
 
   // The candidate list of an unresolved_dot_expr is the candidate list of the
   // base uncurried by one level, and we refer to the name of the member, not to
   // the name of any base.
   if (auto UDE = dyn_cast<UnresolvedDotExpr>(fn)) {
     declName = UDE->getName().getBaseName().userFacingName();
-    uncurryLevel = 1;
+    hasCurriedSelf = true;
 
     // If base is a module or metatype, this is just a simple
     // reference so its curry level should be 0.
     if (auto *DRE = dyn_cast<DeclRefExpr>(UDE->getBase())) {
       if (auto baseType = DRE->getType())
-        uncurryLevel =
-            (baseType->is<ModuleType>() || baseType->is<AnyMetatypeType>()) ? 0
-                                                                            : 1;
+        hasCurriedSelf = !(baseType->is<ModuleType>() ||
+                           baseType->is<AnyMetatypeType>());
     }
 
     // If we actually resolved the member to use, return it.
     auto loc = CS.getConstraintLocator(UDE, ConstraintLocator::Member);
     if (auto *member = CS.findResolvedMemberRef(loc)) {
-      candidates.push_back({ member, uncurryLevel });
+      candidates.push_back({ member, hasCurriedSelf });
       return;
     }
 
     // If we resolved the constructor member, return it.
     auto ctorLoc =
     CS.getConstraintLocator(UDE, ConstraintLocator::ConstructorMember);
     if (auto *member = CS.findResolvedMemberRef(ctorLoc)) {
-      candidates.push_back({ member, uncurryLevel });
+      candidates.push_back({ member, hasCurriedSelf });
       return;
     }
 
@@ -754,7 +752,7 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
   }
 
   if (isa<MemberRefExpr>(fn))
-    uncurryLevel = 1;
+    hasCurriedSelf = true;
 
   // Scan to see if we have a disjunction constraint for this callee.
   for (auto &constraint : CS.getConstraints()) {
@@ -768,7 +766,7 @@ void CalleeCandidateInfo::collectCalleeCandidates(Expr *fn,
         continue;
       auto c = bindOverload->getOverloadChoice();
       if (c.isDecl())
-        candidates.push_back({ c.getDecl(), uncurryLevel });
+        candidates.push_back({ c.getDecl(), hasCurriedSelf });
     }
 
     // If we found some candidates, then we're done.
@@ -865,13 +863,13 @@ CalleeCandidateInfo::CalleeCandidateInfo(Type baseType,
     auto decl = cand.getDecl();
 
     // If this is a method or enum case member (not a var or subscript), then
-    // the uncurry level is 1 if self has already been applied.
-    unsigned uncurryLevel = 0;
+    // we need to skip `self` if it has already been applied.
+    bool hasCurriedSelf = false;
     if (decl->getDeclContext()->isTypeContext() &&
         selfAlreadyApplied && !isa<SubscriptDecl>(decl))
-      uncurryLevel = 1;
+      hasCurriedSelf = true;
 
-    candidates.push_back({ decl, uncurryLevel });
+    candidates.push_back({ decl, hasCurriedSelf });
 
     // If we have a base type for this member, try to perform substitutions into
     // it to get a simpler and more concrete type.

lib/Sema/CalleeCandidateInfo.h

@@ -59,7 +59,7 @@ namespace swift {
   ///
   struct UncurriedCandidate {
     PointerUnion<ValueDecl *, Expr*> declOrExpr;
-    unsigned level;
+    bool skipCurriedSelf;
     Type entityType;
 
     // If true, entityType is written in terms of caller archetypes,
@@ -71,9 +71,10 @@ namespace swift {
     // FIXME: Clean this up.
     bool substituted;
 
-    UncurriedCandidate(ValueDecl *decl, unsigned level);
+    UncurriedCandidate(ValueDecl *decl, bool skipCurriedSelf);
     UncurriedCandidate(Expr *expr, Type type)
-    : declOrExpr(expr), level(0), entityType(type), substituted(true) {}
+    : declOrExpr(expr), skipCurriedSelf(false), entityType(type),
+      substituted(true) {}
 
     ValueDecl *getDecl() const {
       return declOrExpr.dyn_cast<ValueDecl*>();
@@ -86,12 +87,11 @@ namespace swift {
     Type getUncurriedType() const {
       // Start with the known type of the decl.
       auto type = entityType;
-      for (unsigned i = 0, e = level; i != e; ++i) {
+      if (skipCurriedSelf) {
         auto funcTy = type->getAs<AnyFunctionType>();
         if (!funcTy) return Type();
         type = funcTy->getResult();
       }
-      
       return type;
     }