[clang-tools-extra] [llvm] [clang-doc] Adds a mustache backend (PR #133161)

[Paul Kirth via llvm-commits]

================
@@ -32,6 +33,183 @@ populateParentNamespaces(llvm::SmallVector<Reference, 4> &Namespaces,
 
 static void populateMemberTypeInfo(MemberTypeInfo &I, const FieldDecl *D);
 
+void getTemplateParameters(const TemplateParameterList *TemplateParams, 
+                           llvm::raw_ostream &Stream) {
+  Stream << "template <";
+  
+  for (unsigned i = 0; i < TemplateParams->size(); ++i) {
+    if (i > 0) {
+      Stream << ", ";
+    }
+
+    const NamedDecl *Param = TemplateParams->getParam(i);
+    if (const auto *TTP = llvm::dyn_cast<TemplateTypeParmDecl>(Param)) {
+      if (TTP->wasDeclaredWithTypename()) {
+        Stream << "typename";
+      } else {
+        Stream << "class";
+      }
+      if (TTP->isParameterPack()) {
+        Stream << "...";
+      }
+      Stream << " " << TTP->getNameAsString();
+    } else if (const auto *NTTP = llvm::dyn_cast<NonTypeTemplateParmDecl>(Param)) {
+      NTTP->getType().print(Stream, NTTP->getASTContext().getPrintingPolicy());
+      if (NTTP->isParameterPack()) {
+        Stream << "...";
+      }
+      Stream << " " << NTTP->getNameAsString();
+    } else if (const auto *TTPD = llvm::dyn_cast<TemplateTemplateParmDecl>(Param)) {
+      Stream << "template <";
+      getTemplateParameters(TTPD->getTemplateParameters(), Stream);
+      Stream << "> class " << TTPD->getNameAsString();
+    }
+  }
+
+  Stream << "> ";
+}
+
+// Extract the full function prototype from a FunctionDecl including 
+// Full Decl
+llvm::SmallString<256> getFunctionPrototype(const FunctionDecl *FuncDecl) {
+  llvm::SmallString<256> Result; 
+  llvm::raw_svector_ostream Stream(Result);
+  const ASTContext& Ctx = FuncDecl->getASTContext();
+  const auto *Method = llvm::dyn_cast<CXXMethodDecl>(FuncDecl);
+  // If it's a templated function, handle the template parameters
+  if (const auto *TmplDecl = FuncDecl->getDescribedTemplate()) {
+    getTemplateParameters(TmplDecl->getTemplateParameters(), Stream);
+  }
+  // If it's a virtual method
+  if (Method) {
+    if (Method->isVirtual())
+    {
+      Stream << "virtual ";
+    }
+  }
+  // Print return type
+  FuncDecl->getReturnType().print(Stream, Ctx.getPrintingPolicy());
+
+  // Print function name
+  Stream << " " << FuncDecl->getNameAsString() << "(";
+
+  // Print parameter list with types, names, and default values
+  for (unsigned I = 0; I < FuncDecl->getNumParams(); ++I) {
+    if (I > 0) {
+      Stream << ", ";
+    }
+    const ParmVarDecl *ParamDecl = FuncDecl->getParamDecl(I);
+    QualType ParamType = ParamDecl->getType();
+    ParamType.print(Stream, Ctx.getPrintingPolicy());
+
+    // Print parameter name if it has one
+    if (!ParamDecl->getName().empty()) {
+      Stream << " " << ParamDecl->getNameAsString();
+    }
+
+    // Print default argument if it exists
+    if (ParamDecl->hasDefaultArg()) {
+      const Expr *DefaultArg = ParamDecl->getDefaultArg();
+      if (DefaultArg) {
+        Stream << " = ";
+        DefaultArg->printPretty(Stream, nullptr, Ctx.getPrintingPolicy());
+      }
----------------
ilovepi wrote:

DefaultArg only gets used in the conditional. you can use

```
if(const Expr* DefaultArg = ...){ ... }
```

https://github.com/llvm/llvm-project/pull/133161