[clang][ExtractAPI] improve template argument name deduction

[evelez7]

The names of template arguments in partial specializations or parameters used as types might be mangled according to index and depth. Instead of looping through parameter lists to find matches like we do now, they can be deduced via their QualTypes or as written from the AST.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Erick Velez (evelez7)

Changes

The names of template arguments in partial specializations or parameters used as types might be mangled according to index and depth. Instead of looping through parameter lists to find matches like we do now, they can be deduced via their QualTypes or as written from the AST.

---

Full diff: https://github.com/llvm/llvm-project/pull/77716.diff

4 Files Affected:

• (modified) clang/include/clang/ExtractAPI/DeclarationFragments.h (+7-15)
• (modified) clang/lib/ExtractAPI/DeclarationFragments.cpp (+16-42)
• (modified) clang/test/ExtractAPI/class_template_partial_spec.cpp (+1-2)
• (modified) clang/test/ExtractAPI/global_var_template_partial_spec.cpp (+1-2)

diff --git a/clang/include/clang/ExtractAPI/DeclarationFragments.h b/clang/include/clang/ExtractAPI/DeclarationFragments.h
index d719196b9a43ec..5af4a01fa6bb9c 100644
--- a/clang/include/clang/ExtractAPI/DeclarationFragments.h
+++ b/clang/include/clang/ExtractAPI/DeclarationFragments.h
@@ -27,8 +27,6 @@
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/Specifiers.h"
 #include "clang/Lex/MacroInfo.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringRef.h"
 #include <vector>
 
 namespace clang {
@@ -67,6 +65,9 @@ class DeclarationFragments {
     /// parameters.
     GenericParameter,
 
+    /// Argument for partial template specialization.
+    GenericArgument,
+
     /// External parameters in Objective-C methods.
     /// For example, \c forKey in
     /// \code{.m}
@@ -314,13 +315,9 @@ class DeclarationFragmentsBuilder {
   static DeclarationFragments
       getFragmentsForTemplateParameters(ArrayRef<NamedDecl *>);
 
-  static std::string
-  getNameForTemplateArgument(const ArrayRef<NamedDecl *>, std::string);
-
-  static DeclarationFragments
-  getFragmentsForTemplateArguments(const ArrayRef<TemplateArgument>,
-                                   ASTContext &,
-                                   const std::optional<ArrayRef<NamedDecl *>>);
+  static DeclarationFragments getFragmentsForTemplateArguments(
+      const ArrayRef<TemplateArgument>, ASTContext &,
+      const std::optional<ArrayRef<TemplateArgumentLoc>>);
 
   static DeclarationFragments getFragmentsForConcept(const ConceptDecl *);
 
@@ -430,12 +427,7 @@ DeclarationFragmentsBuilder::getFunctionSignature(const FunctionT *Function) {
       dyn_cast<FunctionDecl>(Function)->getDescribedFunctionTemplate() &&
       ReturnType.begin()->Spelling.substr(0, 14).compare("type-parameter") ==
           0) {
-    std::string ProperArgName =
-        getNameForTemplateArgument(dyn_cast<FunctionDecl>(Function)
-                                       ->getDescribedFunctionTemplate()
-                                       ->getTemplateParameters()
-                                       ->asArray(),
-                                   ReturnType.begin()->Spelling);
+    std::string ProperArgName = Function->getReturnType().getAsString();
     ReturnType.begin()->Spelling.swap(ProperArgName);
   }
   ReturnType.append(std::move(After));
diff --git a/clang/lib/ExtractAPI/DeclarationFragments.cpp b/clang/lib/ExtractAPI/DeclarationFragments.cpp
index eb6eea0aaf5465..2c82aeab6083ba 100644
--- a/clang/lib/ExtractAPI/DeclarationFragments.cpp
+++ b/clang/lib/ExtractAPI/DeclarationFragments.cpp
@@ -14,14 +14,11 @@
 #include "clang/ExtractAPI/DeclarationFragments.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
-#include "clang/AST/QualTypeNames.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeLoc.h"
-#include "clang/Basic/OperatorKinds.h"
 #include "clang/ExtractAPI/TypedefUnderlyingTypeResolver.h"
 #include "clang/Index/USRGeneration.h"
 #include "llvm/ADT/StringSwitch.h"
-#include <typeinfo>
 
 using namespace clang::extractapi;
 using namespace llvm;
@@ -102,6 +99,8 @@ StringRef DeclarationFragments::getFragmentKindString(
     return "internalParam";
   case DeclarationFragments::FragmentKind::Text:
     return "text";
+  case DeclarationFragments::FragmentKind::GenericArgument:
+    return "genericArgument";
   }
 
   llvm_unreachable("Unhandled FragmentKind");
@@ -122,6 +121,8 @@ DeclarationFragments::parseFragmentKindFromString(StringRef S) {
       .Case("internalParam", DeclarationFragments::FragmentKind::InternalParam)
       .Case("externalParam", DeclarationFragments::FragmentKind::ExternalParam)
       .Case("text", DeclarationFragments::FragmentKind::Text)
+      .Case("genericArgument",
+            DeclarationFragments::FragmentKind::GenericArgument)
       .Default(DeclarationFragments::FragmentKind::None);
 }
 
@@ -535,9 +536,7 @@ DeclarationFragmentsBuilder::getFragmentsForVarTemplate(const VarDecl *Var) {
       getFragmentsForType(T, Var->getASTContext(), After);
   if (ArgumentFragment.begin()->Spelling.substr(0, 14).compare(
           "type-parameter") == 0) {
-    std::string ProperArgName = getNameForTemplateArgument(
-        Var->getDescribedVarTemplate()->getTemplateParameters()->asArray(),
-        ArgumentFragment.begin()->Spelling);
+    std::string ProperArgName = T.getAsString();
     ArgumentFragment.begin()->Spelling.swap(ProperArgName);
   }
   Fragments.append(std::move(ArgumentFragment))
@@ -570,12 +569,7 @@ DeclarationFragmentsBuilder::getFragmentsForParam(const ParmVarDecl *Param) {
 
   if (TypeFragments.begin()->Spelling.substr(0, 14).compare("type-parameter") ==
       0) {
-    std::string ProperArgName = getNameForTemplateArgument(
-        dyn_cast<FunctionDecl>(Param->getDeclContext())
-            ->getDescribedFunctionTemplate()
-            ->getTemplateParameters()
-            ->asArray(),
-        TypeFragments.begin()->Spelling);
+    std::string ProperArgName = Param->getOriginalType().getAsString();
     TypeFragments.begin()->Spelling.swap(ProperArgName);
   }
 
@@ -668,11 +662,7 @@ DeclarationFragmentsBuilder::getFragmentsForFunction(const FunctionDecl *Func) {
       getFragmentsForType(Func->getReturnType(), Func->getASTContext(), After);
   if (ReturnValueFragment.begin()->Spelling.substr(0, 14).compare(
           "type-parameter") == 0) {
-    std::string ProperArgName =
-        getNameForTemplateArgument(Func->getDescribedFunctionTemplate()
-                                       ->getTemplateParameters()
-                                       ->asArray(),
-                                   ReturnValueFragment.begin()->Spelling);
+    std::string ProperArgName = Func->getReturnType().getAsString();
     ReturnValueFragment.begin()->Spelling.swap(ProperArgName);
   }
 
@@ -958,25 +948,6 @@ DeclarationFragmentsBuilder::getFragmentsForTemplateParameters(
   return Fragments;
 }
 
-// Find the name of a template argument from the template's parameters.
-std::string DeclarationFragmentsBuilder::getNameForTemplateArgument(
-    const ArrayRef<NamedDecl *> TemplateParameters, std::string TypeParameter) {
-  // The arg is a generic parameter from a partial spec, e.g.
-  // T in template<typename T> Foo<T, int>.
-  //
-  // Those names appear as "type-parameter-<index>-<depth>", so we must find its
-  // name from the template's parameter list.
-  for (unsigned i = 0; i < TemplateParameters.size(); ++i) {
-    const auto *Parameter =
-        dyn_cast<TemplateTypeParmDecl>(TemplateParameters[i]);
-    if (TypeParameter.compare("type-parameter-" +
-                              std::to_string(Parameter->getDepth()) + "-" +
-                              std::to_string(Parameter->getIndex())) == 0)
-      return std::string(TemplateParameters[i]->getName());
-  }
-  llvm_unreachable("Could not find the name of a template argument.");
-}
-
 // Get fragments for template arguments, e.g. int in template<typename T>
 // Foo<int>;
 //
@@ -986,7 +957,7 @@ std::string DeclarationFragmentsBuilder::getNameForTemplateArgument(
 DeclarationFragments
 DeclarationFragmentsBuilder::getFragmentsForTemplateArguments(
     const ArrayRef<TemplateArgument> TemplateArguments, ASTContext &Context,
-    const std::optional<ArrayRef<NamedDecl *>> TemplateParameters) {
+    const std::optional<ArrayRef<TemplateArgumentLoc>> TemplateArgumentLocs) {
   DeclarationFragments Fragments;
   for (unsigned i = 0, end = TemplateArguments.size(); i != end; ++i) {
     if (i)
@@ -1000,9 +971,12 @@ DeclarationFragmentsBuilder::getFragmentsForTemplateArguments(
 
     if (ArgumentFragment.begin()->Spelling.substr(0, 14).compare(
             "type-parameter") == 0) {
-      std::string ProperArgName = getNameForTemplateArgument(
-          TemplateParameters.value(), ArgumentFragment.begin()->Spelling);
-      ArgumentFragment.begin()->Spelling.swap(ProperArgName);
+      std::string ProperArgName = TemplateArgumentLocs.value()[i]
+                                      .getTypeSourceInfo()
+                                      ->getType()
+                                      .getAsString();
+      ArgumentFragment = DeclarationFragments().append(
+          ProperArgName, DeclarationFragments::FragmentKind::GenericArgument);
     }
     Fragments.append(std::move(ArgumentFragment));
 
@@ -1086,7 +1060,7 @@ DeclarationFragmentsBuilder::getFragmentsForClassTemplatePartialSpecialization(
       .append("<", DeclarationFragments::FragmentKind::Text)
       .append(getFragmentsForTemplateArguments(
           Decl->getTemplateArgs().asArray(), Decl->getASTContext(),
-          Decl->getTemplateParameters()->asArray()))
+          Decl->getTemplateArgsAsWritten()->arguments()))
       .append(">", DeclarationFragments::FragmentKind::Text)
       .append(";", DeclarationFragments::FragmentKind::Text);
 }
@@ -1127,7 +1101,7 @@ DeclarationFragmentsBuilder::getFragmentsForVarTemplatePartialSpecialization(
       .append("<", DeclarationFragments::FragmentKind::Text)
       .append(getFragmentsForTemplateArguments(
           Decl->getTemplateArgs().asArray(), Decl->getASTContext(),
-          Decl->getTemplateParameters()->asArray()))
+          Decl->getTemplateArgsAsWritten()->arguments()))
       .append(">", DeclarationFragments::FragmentKind::Text)
       .append(";", DeclarationFragments::FragmentKind::Text);
 }
diff --git a/clang/test/ExtractAPI/class_template_partial_spec.cpp b/clang/test/ExtractAPI/class_template_partial_spec.cpp
index eba069319ce450..fc21d61297e4b9 100644
--- a/clang/test/ExtractAPI/class_template_partial_spec.cpp
+++ b/clang/test/ExtractAPI/class_template_partial_spec.cpp
@@ -196,8 +196,7 @@ template<typename Z> class Foo<Z, int> {};
           "spelling": "<"
         },
         {
-          "kind": "typeIdentifier",
-          "preciseIdentifier": "c:t0.0",
+          "kind": "genericArgument",
           "spelling": "Z"
         },
         {
diff --git a/clang/test/ExtractAPI/global_var_template_partial_spec.cpp b/clang/test/ExtractAPI/global_var_template_partial_spec.cpp
index e98076cdb1d016..cca571ff1999fe 100644
--- a/clang/test/ExtractAPI/global_var_template_partial_spec.cpp
+++ b/clang/test/ExtractAPI/global_var_template_partial_spec.cpp
@@ -206,8 +206,7 @@ template<typename Z> int Foo<int, Z> = 0;
           "spelling": ", "
         },
         {
-          "kind": "typeIdentifier",
-          "preciseIdentifier": "c:t0.0",
+          "kind": "genericArgument",
           "spelling": "Z"
         },
         {

[evelez7]

ping

[daniel-grumberg]

Looks like the right thing to me!

[evelez7]

In this patch getFragmentsForTemplateArguments, which is being called here, is changed to accept ArrayRef<TemplateArgumentLoc> (which is what the changed line returns) instead of ArrayRef<NamedDecl *> because of the nasty loop that was deleted in DeclarationFragments.cpp:962. A TemplateArgumentLoc gives us the name of the specialization's type argument directly, instead of comparing with the declaration's template parameters.