Sema: Add DeclContext::isGenericTypeContext()

Once nested generic parameter lists are properly chained, we need a
way of checking if we're inside a generic type context that's
distinct from just checking if we have a generic type signature
available.

This distinguishes between these two cases:

class A<T> {
  // generic signature
  func method() -> T { // <T> A<T> -> () -> T
  }
}

func f<T>() {
  class A {
    // no generic signature
    func method() -> T { // A -> () -> T
    }
  }
}

Author: slavapestov

include/swift/AST/DeclContext.h

@@ -359,6 +359,10 @@ class alignas(1 << DeclContextAlignInBits) DeclContext {
 
   /// Determine whether the innermost context is generic.
   bool isInnermostContextGeneric() const;
+  
+  /// Determine whether the innermost context is either a generic type context,
+  /// or a concrete type nested inside a generic type context.
+  bool isGenericTypeContext() const;
 
   /// Returns true if lookups within this context could affect downstream files.
   ///

lib/AST/Decl.cpp

@@ -4138,8 +4138,9 @@ void EnumElementDecl::computeType() {
   if (getArgumentType())
     resultTy = FunctionType::get(getArgumentType(), resultTy);
 
-  if (auto gp = ED->getGenericParamsOfContext())
-    resultTy = PolymorphicFunctionType::get(argTy, resultTy, gp);
+  if (ED->isGenericTypeContext())
+    resultTy = PolymorphicFunctionType::get(argTy, resultTy,
+                                            ED->getGenericParamsOfContext());
   else
     resultTy = FunctionType::get(argTy, resultTy);
 

lib/AST/DeclContext.cpp

@@ -404,10 +404,11 @@ DeclContext *DeclContext::getModuleScopeContext() const {
 
 /// Determine whether the given context is generic at any level.
 bool DeclContext::isGenericContext() const {
-  for (const DeclContext *dc = this; ; dc = dc->getParent() ) {
+  for (const DeclContext *dc = this; ; dc = dc->getParent()) {
     switch (dc->getContextKind()) {
     case DeclContextKind::Module:
     case DeclContextKind::FileUnit:
+    case DeclContextKind::TopLevelCodeDecl:
       return false;
 
     case DeclContextKind::Initializer:
@@ -421,10 +422,6 @@ bool DeclContext::isGenericContext() const {
         return true;
       continue;
 
-    case DeclContextKind::TopLevelCodeDecl:
-      // Check parent context.
-      continue;
-
     case DeclContextKind::NominalTypeDecl:
       if (cast<NominalTypeDecl>(dc)->getGenericParams())
         return true;
@@ -440,6 +437,17 @@ bool DeclContext::isGenericContext() const {
   llvm_unreachable("illegal declcontext hierarchy");
 }
 
+/// Determine whether the given context nested inside a generic type context
+/// with no local contexts in between.
+bool DeclContext::isGenericTypeContext() const {
+  for (const auto *dc = this; dc->isTypeContext(); dc = dc->getParent()) {
+    if (dc->isInnermostContextGeneric())
+      return true;
+  }
+  
+  return false;
+}
+
 /// Determine whether the innermost context is generic.
 bool DeclContext::isInnermostContextGeneric() const {
   switch (getContextKind()) {

lib/Sema/TypeCheckDecl.cpp

@@ -1440,7 +1440,7 @@ void swift::configureConstructorType(ConstructorDecl *ctor,
     fnType = FunctionType::get(argType, resultType, extInfo);
   }
   Type selfMetaType = MetatypeType::get(selfType->getInOutObjectType());
-  if (outerGenericParams) {
+  if (ctor->getDeclContext()->isGenericTypeContext()) {
     allocFnType = PolymorphicFunctionType::get(selfMetaType, fnType,
                                                outerGenericParams);
     initFnType = PolymorphicFunctionType::get(selfType, fnType,
@@ -3671,7 +3671,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     GenericParamList *outerGenericParams = nullptr;
     auto patterns = FD->getBodyParamPatterns();
     bool hasSelf = FD->getDeclContext()->isTypeContext();
-    if (hasSelf)
+    if (FD->getDeclContext()->isGenericTypeContext())
       outerGenericParams = FD->getDeclContext()->getGenericParamsOfContext();
 
     for (unsigned i = 0, e = patterns.size(); i != e; ++i) {
@@ -4042,7 +4042,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
         // Assign archetypes.
         finalizeGenericParamList(builder, gp, FD, TC);
       }
-    } else if (outerGenericParams) {
+    } else if (FD->getDeclContext()->isGenericTypeContext()) {
       if (TC.validateGenericFuncSignature(FD)) {
         markInvalidGenericSignature(FD, TC);
       } else if (!FD->hasType()) {
@@ -5168,7 +5168,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     auto resultTy = TC.getInterfaceTypeFromInternalType(enumDecl,
                                                         funcTy->getResult());
     auto interfaceTy
-      = GenericFunctionType::get(enumDecl->getGenericSignature(),
+      = GenericFunctionType::get(enumDecl->getGenericSignatureOfContext(),
                                  inputTy, resultTy, funcTy->getExtInfo());
 
     // Record the interface type.
@@ -5247,7 +5247,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     // case the enclosing enum type was illegally declared inside of a generic
     // context. (In that case, we'll post a diagnostic while visiting the
     // parent enum.)
-    if (ED->getGenericParams())
+    if (EED->getDeclContext()->isGenericTypeContext())
       computeEnumElementInterfaceType(EED);
 
     // Require the carried type to be materializable.
@@ -5419,7 +5419,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
         // Assign archetypes.
         finalizeGenericParamList(builder, gp, CD, TC);
       }
-    } else if (outerGenericParams) {
+    } else if (CD->getDeclContext()->isGenericTypeContext()) {
       if (TC.validateGenericFuncSignature(CD)) {
         CD->setInvalid();
       } else {
@@ -5565,7 +5565,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     GenericParamList *outerGenericParams;
     Type SelfTy = configureImplicitSelf(TC, DD, outerGenericParams);
 
-    if (outerGenericParams)
+    if (DD->getDeclContext()->isGenericTypeContext())
       TC.validateGenericFuncSignature(DD);
 
     if (semaFuncParamPatterns(DD)) {
@@ -5574,7 +5574,7 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     }
 
     Type FnTy;
-    if (outerGenericParams)
+    if (DD->getDeclContext()->isGenericTypeContext())
       FnTy = PolymorphicFunctionType::get(SelfTy,
                                           TupleType::getEmpty(TC.Context),
                                           outerGenericParams);

validation-test/compiler_crashers/25819-std-function-func-swift-type-subst.swift renamed to validation-test/compiler_crashers_fixed/25819-std-function-func-swift-type-subst.swift

@@ -1,4 +1,4 @@
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 
 // Distributed under the terms of the MIT license
 // Test case submitted to project by https://github.com/practicalswift (practicalswift)

validation-test/compiler_crashers/26568-swift-typechecker-validatedecl.swift renamed to validation-test/compiler_crashers_fixed/26568-swift-typechecker-validatedecl.swift

@@ -1,4 +1,4 @@
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 // Distributed under the terms of the MIT license
 // Test case submitted to project by https://github.com/practicalswift (practicalswift)
 // Test case found by fuzzing

validation-test/compiler_crashers/26922-swift-constraints-constraintsystem-opengeneric.swift renamed to validation-test/compiler_crashers_fixed/26922-swift-constraints-constraintsystem-opengeneric.swift

@@ -1,4 +1,4 @@
-// RUN: not --crash %target-swift-frontend %s -parse
+// RUN: not %target-swift-frontend %s -parse
 
 // Distributed under the terms of the MIT license
 // Test case submitted to project by https://github.com/practicalswift (practicalswift)