[CodeComplete] Member completion: heuristically resolve some dependent base exprs

[sammccall]

Summary

Today, inside a template, you can get completion for:

Foo<T> t;
t.^

t has dependent type Foo<T>, and we use the primary template to find its members.
However we also want this to work:

t.foo.bar().^

The type of t.foo.bar() is DependentTy, so we attempt to resolve using similar
heuristics (e.g. primary template).

[sammccall]

Also handle parens and unresolved calls

[hokein]

thanks! this looks like a nice improvement!

clang/test/CodeCompletion/member-access.cpp

88

hmm, inserting new code here will shift all offsets of below code, I would append a new test in this file to keep a clearer history. but up to you.

[sammccall]

clang/test/CodeCompletion/member-access.cpp

88

I see your point about history, but I find myself navigating these tests by semantics more often than by history, and this seems closely related to the existing completeDependentMembers cases.

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

 template <template <class> class TT> int foo() {
   int a = ^
 }
 )cpp")
                          .Completions;
   EXPECT_THAT(Completions, Contains(Named("TT")));
 }
 
+TEST(CompletionTest, NestedTemplateHeuristics) {
+  auto Completions = completions(R"cpp(
+struct Plain { int xxx; };
+template <typename T> class Templ { Plain ppp; };
+template <typename T> void foo(Templ<T> &t) {
+  // Formally ppp has DependentTy, because Templ may be specialized.
+  // However we sholud be able to see into it using the primary template.
+  t.ppp.^
+}
+)cpp")
+                         .Completions;
+  EXPECT_THAT(Completions, Contains(Named("xxx")));
+}
+
 TEST(CompletionTest, RecordCCResultCallback) {
   std::vector<CodeCompletion> RecordedCompletions;
   CodeCompleteOptions Opts;
   Opts.RecordCCResult = [&RecordedCompletions](const CodeCompletion &CC,
                                                const SymbolQualitySignals &,
                                                const SymbolRelevanceSignals &,
                                                float Score) {
     RecordedCompletions.push_back(CC);

clang/lib/Sema/SemaCodeComplete.cpp

if (DN.isIdentifier() && DN.getAsIdentifierInfo()->isStr("same_as"))
           if (Arg.getKind() == TemplateArgument::Type)
             return Arg.getAsType();
         }
     return {};
   }
 
   llvm::DenseMap<const IdentifierInfo *, Member> Results;
 };
+
+// Returns a type for E that yields acceptable member completions.
+// In particular, when E->getType() is DependentTy, try to guess a likely type.
+// We accept some lossiness (like dropping parameters).
+// We only try to handle common expressions on the LHS of MemberExpr.
+QualType getApproximateType(const Expr *E) {
+  QualType T = E->getType();
+  if (!T.isNull() && !T->isSpecificBuiltinType(BuiltinType::Dependent))
+    return T;
+  // A call: approximate-resolve callee to a function type, get its return type
+  if (const CallExpr *CE = llvm::dyn_cast<CallExpr>(E)) {
+    QualType Callee = getApproximateType(CE->getCallee());
+    if (Callee.isNull() ||
+        Callee->isSpecificPlaceholderType(BuiltinType::BoundMember))
+      Callee = Expr::findBoundMemberType(CE->getCallee());
+    if (Callee.isNull())
+      return QualType();
+
+    if (const auto *FnTypePtr = Callee->getAs<PointerType>()) {
+      Callee = FnTypePtr->getPointeeType();
+    } else if (const auto *BPT = Callee->getAs<BlockPointerType>()) {
+      Callee = BPT->getPointeeType();
+    }
+    if (const FunctionType *FnType = Callee->getAs<FunctionType>())
+      return FnType->getReturnType().getNonReferenceType();
+  }
+  // A dependent member: approximate-resolve the base, then lookup.
+  if (const auto *CDSME = llvm::dyn_cast<CXXDependentScopeMemberExpr>(E)) {
+    QualType Base = CDSME->isImplicitAccess()
+                        ? CDSME->getBaseType()
+                        : getApproximateType(CDSME->getBase());
+    if (CDSME->isArrow() && !Base.isNull())
+      Base = Base->getPointeeType(); // could handle unique_ptr etc here?
+    RecordDecl *RD = Base.isNull() ? nullptr : getAsRecordDecl(Base);
+    if (RD && RD->isCompleteDefinition()) {
+      for (const auto &Member : RD->lookup(CDSME->getMember()))
+        if (const ValueDecl *VD = llvm::dyn_cast<ValueDecl>(Member))
+          return VD->getType().getNonReferenceType();
+    }
+  }
+  return QualType();
+}
+
 } // namespace
 
 void Sema::CodeCompleteMemberReferenceExpr(Scope *S, Expr *Base,
                                            Expr *OtherOpBase,
                                            SourceLocation OpLoc, bool IsArrow,
                                            bool IsBaseExprStatement,
                                            QualType PreferredType) {
   if (!Base || !CodeCompleter)
     return;
 
   // Peel off the ParenListExpr by chosing the last one, as they don't have a
   // predefined type.
   if (auto *PLE = llvm::dyn_cast<ParenListExpr>(Base))
     Base = PLE->getExpr(PLE->getNumExprs() - 1);
   if (OtherOpBase) {
     if (auto *PLE = llvm::dyn_cast<ParenListExpr>(OtherOpBase))
       OtherOpBase = PLE->getExpr(PLE->getNumExprs() - 1);
   }
 
   ExprResult ConvertedBase = PerformMemberExprBaseConversion(Base, IsArrow);
   if (ConvertedBase.isInvalid())
     return;
-  QualType ConvertedBaseType = ConvertedBase.get()->getType();
+  QualType ConvertedBaseType = getApproximateType(ConvertedBase.get());
 
   enum CodeCompletionContext::Kind contextKind;
 
   if (IsArrow) {
     if (const auto *Ptr = ConvertedBaseType->getAs<PointerType>())
       ConvertedBaseType = Ptr->getPointeeType();
   }
 
auto DoCompletion = [&](Expr *Base, bool IsArrow,
     if (!Base)
       return false;
 
     ExprResult ConvertedBase = PerformMemberExprBaseConversion(Base, IsArrow);
     if (ConvertedBase.isInvalid())
       return false;
     Base = ConvertedBase.get();
 
-    QualType BaseType = Base->getType();
+    QualType BaseType = getApproximateType(Base);
     if (BaseType.isNull())
       return false;
     ExprValueKind BaseKind = Base->getValueKind();
 
     if (IsArrow) {
       if (const PointerType *Ptr = BaseType->getAs<PointerType>()) {
         BaseType = Ptr->getPointeeType();
         BaseKind = VK_LValue;

clang/test/CodeCompletion/member-access.cpp

 };
 
 template<typename T, typename S>
 class TemplateClass: public Base1 , public BaseTemplate<T> {
 public:
   T function() { }
   T field;
 
+  TemplateClass<S, T> &relatedField;
+  BaseTemplate<S> &relatedFunction();
+
   void overload1(const T &);
   void overload1(const S &);
 };
 
 template<typename T, typename S>
 void completeDependentMembers(TemplateClass<T, S> &object,
                               TemplateClass<int, S> *object2) {
   object.field;
   object2->field;
 // CHECK-CC2: baseTemplateField (InBase) : [#T#][#BaseTemplate<T>::#]baseTemplateField
 // CHECK-CC2: baseTemplateFunction (InBase) : [#T#][#BaseTemplate<T>::#]baseTemplateFunction()
 // CHECK-CC2: field : [#T#]field
 // CHECK-CC2: function : [#T#]function()
 // CHECK-CC2: member1 (InBase) : [#int#][#Base1::#]member1
 // CHECK-CC2: member2 (InBase) : [#float#][#Base1::#]member2
 // CHECK-CC2: overload1 : [#void#]overload1(<#const T &#>)
 // CHECK-CC2: overload1 : [#void#]overload1(<#const S &#>)
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:94:10 %s -o - | FileCheck -check-prefix=CHECK-CC2 %s
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:95:12 %s -o - | FileCheck -check-prefix=CHECK-CC2 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:97:10 %s -o - | FileCheck -check-prefix=CHECK-CC2 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:98:12 %s -o - | FileCheck -check-prefix=CHECK-CC2 %s
+
+  object.relatedField.relatedFunction().baseTemplateField;
+// CHECK-DEP-CHAIN: baseTemplateField : [#T#]baseTemplateField
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:111:41 %s -o - | FileCheck -check-prefix=CHECK-DEP-CHAIN %s
 }
 
 
 void completeDependentSpecializedMembers(TemplateClass<int, double> &object,
                                          TemplateClass<int, double> *object2) {
   object.field;
   object2->field;
 // CHECK-CC3: baseTemplateField (InBase) : [#int#][#BaseTemplate<int>::#]baseTemplateField
 // CHECK-CC3: baseTemplateFunction (InBase) : [#int#][#BaseTemplate<int>::#]baseTemplateFunction()
 // CHECK-CC3: field : [#int#]field
 // CHECK-CC3: function : [#int#]function()
 // CHECK-CC3: member1 (InBase) : [#int#][#Base1::#]member1
 // CHECK-CC3: member2 (InBase) : [#float#][#Base1::#]member2
 // CHECK-CC3: overload1 : [#void#]overload1(<#const int &#>)
 // CHECK-CC3: overload1 : [#void#]overload1(<#const double &#>)
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:112:10 %s -o - | FileCheck -check-prefix=CHECK-CC3 %s
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:113:12 %s -o - | FileCheck -check-prefix=CHECK-CC3 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:119:10 %s -o - | FileCheck -check-prefix=CHECK-CC3 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:120:12 %s -o - | FileCheck -check-prefix=CHECK-CC3 %s
 }
 
 template <typename T>
 class Template {
 public:
   BaseTemplate<int> o1;
   BaseTemplate<T> o2;
 
   void function() {
     o1.baseTemplateField;
 // CHECK-CC4: BaseTemplate : BaseTemplate::
 // CHECK-CC4: baseTemplateField : [#int#]baseTemplateField
 // CHECK-CC4: baseTemplateFunction : [#int#]baseTemplateFunction()
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:134:8 %s -o - | FileCheck -check-prefix=CHECK-CC4 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:141:8 %s -o - | FileCheck -check-prefix=CHECK-CC4 %s
     o2.baseTemplateField;
 // CHECK-CC5: BaseTemplate : BaseTemplate::
 // CHECK-CC5: baseTemplateField : [#T#]baseTemplateField
 // CHECK-CC5: baseTemplateFunction : [#T#]baseTemplateFunction()
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:139:8 %s -o - | FileCheck -check-prefix=CHECK-CC5 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:146:8 %s -o - | FileCheck -check-prefix=CHECK-CC5 %s
     this->o1;
 // CHECK-CC6: [#void#]function()
 // CHECK-CC6: o1 : [#BaseTemplate<int>#]o1
 // CHECK-CC6: o2 : [#BaseTemplate<T>#]o2
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:144:11 %s -o - | FileCheck -check-prefix=CHECK-CC6 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:151:11 %s -o - | FileCheck -check-prefix=CHECK-CC6 %s
   }
 
   static void staticFn(T &obj);
 
   struct Nested { };
 };
 
 template<typename T>
 void dependentColonColonCompletion() {
   Template<T>::staticFn();
 // CHECK-CC7: function : [#void#]function()
 // CHECK-CC7: Nested : Nested
 // CHECK-CC7: o1 : [#BaseTemplate<int>#]o1
 // CHECK-CC7: o2 : [#BaseTemplate<T>#]o2
 // CHECK-CC7: staticFn : [#void#]staticFn(<#T &obj#>)
 // CHECK-CC7: Template : Template
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:158:16 %s -o - | FileCheck -check-prefix=CHECK-CC7 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:165:16 %s -o - | FileCheck -check-prefix=CHECK-CC7 %s
   typename Template<T>::Nested m;
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:166:25 %s -o - | FileCheck -check-prefix=CHECK-CC7 %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:173:25 %s -o - | FileCheck -check-prefix=CHECK-CC7 %s
 }
 
 class Proxy2 {
 public:
   Derived *operator->() const;
   int member5;
 };
 
 void test2(const Proxy2 &p) {
   p->
 }
 
 void test3(const Proxy2 &p) {
   p.
 }
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-with-fixits -code-completion-at=%s:177:6 %s -o - | FileCheck -check-prefix=CHECK-CC8 --implicit-check-not="Derived : Derived(" %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-with-fixits -code-completion-at=%s:184:6 %s -o - | FileCheck -check-prefix=CHECK-CC8 --implicit-check-not="Derived : Derived(" %s
 // CHECK-CC8: Base1 (InBase) : Base1::
 // CHECK-CC8: member1 (InBase) : [#int#][#Base1::#]member1
 // CHECK-CC8: member1 (InBase) : [#int#][#Base2::#]member1
 // CHECK-CC8: member2 (InBase) : [#float#][#Base1::#]member2
 // CHECK-CC8: member3 (InBase) : [#double#][#Base2::#]member3
 // CHECK-CC8: member4 : [#int#]member4
-// CHECK-CC8: member5 : [#int#]member5 (requires fix-it: {177:4-177:6} to ".")
+// CHECK-CC8: member5 : [#int#]member5 (requires fix-it: {184:4-184:6} to ".")
 // CHECK-CC8: memfun1 (InBase) : [#void#][#Base3::#]memfun1(<#float#>)
 // CHECK-CC8: memfun1 (InBase) : [#void#][#Base3::#]memfun1(<#double#>)[# const#]
 // CHECK-CC8: memfun1 (Hidden,InBase) : [#void#]Base2::memfun1(<#int#>)
 // CHECK-CC8: memfun2 (InBase) : [#void#][#Base3::#]memfun2(<#int#>)
 // CHECK-CC8: memfun3 : [#int#]memfun3(<#int#>)
-// CHECK-CC8: operator-> : [#Derived *#]operator->()[# const#] (requires fix-it: {177:4-177:6} to ".")
+// CHECK-CC8: operator-> : [#Derived *#]operator->()[# const#] (requires fix-it: {184:4-184:6} to ".")
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-with-fixits -code-completion-at=%s:181:6 %s -o - | FileCheck -check-prefix=CHECK-CC9 --implicit-check-not="Derived : Derived(" %s
+// RUN: %clang_cc1 -fsyntax-only -code-completion-with-fixits -code-completion-at=%s:188:6 %s -o - | FileCheck -check-prefix=CHECK-CC9 --implicit-check-not="Derived : Derived(" %s
 // CHECK-CC9: Base1 (InBase) : Base1::
-// CHECK-CC9: member1 (InBase) : [#int#][#Base1::#]member1 (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: member1 (InBase) : [#int#][#Base2::#]member1 (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: member2 (InBase) : [#float#][#Base1::#]member2 (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: member3 (InBase) : [#double#][#Base2::#]member3 (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: member4 : [#int#]member4 (requires fix-it: {181:4-181:5} to "->")
+// CHECK-CC9: member1 (InBase) : [#int#][#Base1::#]member1 (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: member1 (InBase) : [#int#][#Base2::#]member1 (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: member2 (InBase) : [#float#][#Base1::#]member2 (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: member3 (InBase) : [#double#][#Base2::#]member3 (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: member4 : [#int#]member4 (requires fix-it: {188:4-188:5} to "->")
 // CHECK-CC9: member5 : [#int#]member5
-// CHECK-CC9: memfun1 (InBase) : [#void#][#Base3::#]memfun1(<#float#>) (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: memfun1 (InBase) : [#void#][#Base3::#]memfun1(<#double#>)[# const#] (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: memfun1 (Hidden,InBase) : [#void#]Base2::memfun1(<#int#>) (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: memfun2 (InBase) : [#void#][#Base3::#]memfun2(<#int#>) (requires fix-it: {181:4-181:5} to "->")
-// CHECK-CC9: memfun3 : [#int#]memfun3(<#int#>) (requires fix-it: {181:4-181:5} to "->")
+// CHECK-CC9: memfun1 (InBase) : [#void#][#Base3::#]memfun1(<#float#>) (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: memfun1 (InBase) : [#void#][#Base3::#]memfun1(<#double#>)[# const#] (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: memfun1 (Hidden,InBase) : [#void#]Base2::memfun1(<#int#>) (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: memfun2 (InBase) : [#void#][#Base3::#]memfun2(<#int#>) (requires fix-it: {188:4-188:5} to "->")
+// CHECK-CC9: memfun3 : [#int#]memfun3(<#int#>) (requires fix-it: {188:4-188:5} to "->")
 // CHECK-CC9: operator-> : [#Derived *#]operator->()[# const#]
 
 // These overload sets differ only by return type and this-qualifiers.
 // So for any given callsite, only one is available.
 struct Overloads {
   double ConstOverload(char);
   int ConstOverload(char) const;
 

 }
 void testRValue() {
   Overloads().
 }
 void testXValue(Overloads& X) {
   static_cast<Overloads&&>(X).
 }
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:225:7 %s -o - | FileCheck -check-prefix=CHECK-LVALUE %s \
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:232:7 %s -o - | FileCheck -check-prefix=CHECK-LVALUE %s \
 // RUN: --implicit-check-not="[#int#]ConstOverload(" \
 // RUN: --implicit-check-not="[#double#]RefOverload(" \
 // RUN: --implicit-check-not="[#char#]RefOverload("
 // CHECK-LVALUE-DAG: [#double#]ConstOverload(
 // CHECK-LVALUE-DAG: [#int#]RefOverload(
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:228:12 %s -o - | FileCheck -check-prefix=CHECK-CONSTLVALUE %s \
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:235:12 %s -o - | FileCheck -check-prefix=CHECK-CONSTLVALUE %s \
 // RUN: --implicit-check-not="[#double#]ConstOverload(" \
 // RUN: --implicit-check-not="[#int#]RefOverload(" \
 // RUN: --implicit-check-not="[#char#]RefOverload("
 // CHECK-CONSTLVALUE: [#int#]ConstOverload(
 // CHECK-CONSTLVALUE: [#double#]RefOverload(
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:231:15 %s -o - | FileCheck -check-prefix=CHECK-PRVALUE %s \
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:238:15 %s -o - | FileCheck -check-prefix=CHECK-PRVALUE %s \
 // RUN: --implicit-check-not="[#int#]ConstOverload(" \
 // RUN: --implicit-check-not="[#int#]RefOverload(" \
 // RUN: --implicit-check-not="[#double#]RefOverload("
 // CHECK-PRVALUE: [#double#]ConstOverload(
 // CHECK-PRVALUE: [#char#]RefOverload(
 
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:234:31 %s -o - | FileCheck -check-prefix=CHECK-XVALUE %s \
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:241:31 %s -o - | FileCheck -check-prefix=CHECK-XVALUE %s \
 // RUN: --implicit-check-not="[#int#]ConstOverload(" \
 // RUN: --implicit-check-not="[#int#]RefOverload(" \
 // RUN: --implicit-check-not="[#double#]RefOverload("
 // CHECK-XVALUE: [#double#]ConstOverload(
 // CHECK-XVALUE: [#char#]RefOverload(
 
 void testOverloadOperator() {
   struct S {
     char operator=(int) const;
     int operator=(int);
   } s;
   return s.
 }
-// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:270:12 %s -o - | FileCheck -check-prefix=CHECK-OPER %s \
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:277:12 %s -o - | FileCheck -check-prefix=CHECK-OPER %s \
 // RUN: --implicit-check-not="[#char#]operator=("
 // CHECK-OPER: [#int#]operator=(
 
 struct S { int member; };
 S overloaded(int);
 S overloaded(double);
 void foo() {
   // No overload matches, but we have recovery-expr with the correct type.
   overloaded().
 }
-// RUN: not %clang_cc1 -fsyntax-only -frecovery-ast -frecovery-ast-type -code-completion-at=%s:281:16 %s -o - | FileCheck -check-prefix=CHECK-RECOVERY %s
+// RUN: not %clang_cc1 -fsyntax-only -frecovery-ast -frecovery-ast-type -code-completion-at=%s:288:16 %s -o - | FileCheck -check-prefix=CHECK-RECOVERY %s
 // CHECK-RECOVERY: [#int#]member