[libclang] Fix cursors for functions with trailing return type

[nik]

Summary

For the function declaration

auto foo5(Foo) -> Foo;

the parameter tokens were mapped to cursors representing the
FunctionDecl:

Keyword: "auto" [1:1 - 1:5] FunctionDecl=test5:1:6
Identifier: "test5" [1:6 - 1:11] FunctionDecl=test5:1:6
Punctuation: "(" [1:11 - 1:12] FunctionDecl=test5:1:6
Identifier: "X" [1:12 - 1:13] FunctionDecl=test5:1:6 // Ops, not a TypeRef
Punctuation: ")" [1:13 - 1:14] FunctionDecl=test5:1:6
Punctuation: "->" [1:15 - 1:17] FunctionDecl=test5:1:6
Identifier: "X" [1:18 - 1:19] TypeRef=struct X:7:8
Punctuation: ";" [1:19 - 1:20]

Fix this by ensuring that the trailing return type is not visited as
first.

[nik]

Ping

[bkramer]

lg

[nik]

Thanks for the review. Please submit as I don't have the permissions for this.

[nik]

Ping..."Please submit as I don't have the permissions for this."

test/Index/annotate-tokens.cpp

void test4() {
   if (int p = 0)
     return;
 }
 
 class C {
   ~C();
 };
 
-// RUN: c-index-test -test-annotate-tokens=%s:1:1:38:1 %s -fno-delayed-template-parsing | FileCheck %s
+auto test5(X) -> X;
+
+// RUN: c-index-test -test-annotate-tokens=%s:1:1:41:1 %s -std=c++14 -fno-delayed-template-parsing | FileCheck %s
 // CHECK: Keyword: "struct" [1:1 - 1:7] StructDecl=bonk:1:8 (Definition)
 // CHECK: Identifier: "bonk" [1:8 - 1:12] StructDecl=bonk:1:8 (Definition)
 // CHECK: Punctuation: "{" [1:13 - 1:14] StructDecl=bonk:1:8 (Definition)
 // CHECK: Punctuation: "}" [1:15 - 1:16] StructDecl=bonk:1:8 (Definition)
 // CHECK: Punctuation: ";" [1:16 - 1:17]
 // CHECK: Keyword: "void" [2:1 - 2:5] FunctionDecl=test:2:6 (Definition)
 // CHECK: Identifier: "test" [2:6 - 2:10] FunctionDecl=test:2:6 (Definition)
 // CHECK: Punctuation: "(" [2:10 - 2:11] FunctionDecl=test:2:6 (Definition)

 // CHECK: Punctuation: "::" [29:13 - 29:15] CXXMethod=foo:29:15 (Definition)
 // CHECK: Identifier: "foo" [29:15 - 29:18] CXXMethod=foo:29:15 (Definition)
 // CHECK: Punctuation: "(" [29:18 - 29:19] CXXMethod=foo:29:15 (Definition)
 // CHECK: Punctuation: ")" [29:19 - 29:20] CXXMethod=foo:29:15 (Definition)
 // CHECK: Punctuation: "{" [29:21 - 29:22] CompoundStmt=
 // CHECK: Punctuation: "}" [29:22 - 29:23] CompoundStmt=
 // CHECK: Punctuation: "~" [37:3 - 37:4] CXXDestructor=~C:37:3
 // CHECK: Identifier: "C" [37:4 - 37:5] CXXDestructor=~C:37:3
+// CHECK: Keyword: "auto" [40:1 - 40:5] FunctionDecl=test5:40:6
+// CHECK: Identifier: "test5" [40:6 - 40:11] FunctionDecl=test5:40:6
+// CHECK: Punctuation: "(" [40:11 - 40:12] FunctionDecl=test5:40:6
+// CHECK: Identifier: "X" [40:12 - 40:13] TypeRef=struct X:7:8
+// CHECK: Punctuation: ")" [40:13 - 40:14] FunctionDecl=test5:40:6
+// CHECK: Punctuation: "->" [40:15 - 40:17] FunctionDecl=test5:40:6
+// CHECK: Identifier: "X" [40:18 - 40:19] TypeRef=struct X:7:8
+// CHECK: Punctuation: ";" [40:19 - 40:20]
 
 // RUN: env LIBCLANG_DISABLE_CRASH_RECOVERY=1 c-index-test -test-annotate-tokens=%s:32:1:32:13 %s | FileCheck %s -check-prefix=CHECK2
 // CHECK2: Keyword: "if" [32:3 - 32:5] IfStmt=
 // CHECK2: Punctuation: "(" [32:6 - 32:7] IfStmt=
 // CHECK2: Keyword: "int" [32:7 - 32:10] VarDecl=p:32:11 (Definition)
 // CHECK2: Identifier: "p" [32:11 - 32:12] VarDecl=p:32:11 (Definition)
 // CHECK2: Punctuation: "=" [32:13 - 32:14] VarDecl=p:32:11 (Definition)

tools/libclang/CIndex.cpp

bool CursorVisitor::VisitDeclaratorDecl(DeclaratorDecl *DD) {
   // Visit the nested-name-specifier, if present.
   if (NestedNameSpecifierLoc QualifierLoc = DD->getQualifierLoc())
     if (VisitNestedNameSpecifierLoc(QualifierLoc))
       return true;
 
   return false;
 }
 
+static bool HasTrailingReturnType(FunctionDecl *ND) {
+  const QualType Ty = ND->getType();
+  if (const FunctionType *AFT = Ty->getAs<FunctionType>()) {
+    if (const FunctionProtoType *FT = dyn_cast<FunctionProtoType>(AFT))
+      return FT->hasTrailingReturn();
+  }
+
+  return false;
+}
+
 /// \brief Compare two base or member initializers based on their source order.
 static int CompareCXXCtorInitializers(CXXCtorInitializer *const *X,
                                       CXXCtorInitializer *const *Y) {
   return (*X)->getSourceOrder() - (*Y)->getSourceOrder();
 }
 
 bool CursorVisitor::VisitFunctionDecl(FunctionDecl *ND) {
   unsigned NumParamList = ND->getNumTemplateParameterLists();
   for (unsigned i = 0; i < NumParamList; i++) {
     TemplateParameterList* Params = ND->getTemplateParameterList(i);
     if (VisitTemplateParameters(Params))
       return true;
   }
 
   if (TypeSourceInfo *TSInfo = ND->getTypeSourceInfo()) {
     // Visit the function declaration's syntactic components in the order
     // written. This requires a bit of work.
     TypeLoc TL = TSInfo->getTypeLoc().IgnoreParens();
     FunctionTypeLoc FTL = TL.getAs<FunctionTypeLoc>();
+    const bool HasTrailingRT = HasTrailingReturnType(ND);
     
     // If we have a function declared directly (without the use of a typedef),
     // visit just the return type. Otherwise, just visit the function's type
     // now.
-    if ((FTL && !isa<CXXConversionDecl>(ND) && Visit(FTL.getReturnLoc())) ||
+    if ((FTL && !isa<CXXConversionDecl>(ND) && !HasTrailingRT &&
+         Visit(FTL.getReturnLoc())) ||
         (!FTL && Visit(TL)))
       return true;
-    
     // Visit the nested-name-specifier, if present.
     if (NestedNameSpecifierLoc QualifierLoc = ND->getQualifierLoc())
       if (VisitNestedNameSpecifierLoc(QualifierLoc))
         return true;
     
     // Visit the declaration name.
     if (!isa<CXXDestructorDecl>(ND))
       if (VisitDeclarationNameInfo(ND->getNameInfo()))
         return true;
     
     // FIXME: Visit explicitly-specified template arguments!
     
     // Visit the function parameters, if we have a function type.
     if (FTL && VisitFunctionTypeLoc(FTL, true))
       return true;
-    
+    // Visit the function's trailing return type.
+    if (FTL && HasTrailingRT && Visit(FTL.getReturnLoc()))
+      return true;
+
     // FIXME: Attributes?
   }
   
   if (ND->doesThisDeclarationHaveABody() && !ND->isLateTemplateParsed()) {
     if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(ND)) {
       // Find the initializers that were written in the source.
       SmallVector<CXXCtorInitializer *, 4> WrittenInits;
       for (auto *I : Constructor->inits()) {