[clangd] Hover: Add CalleeArgInfo for constructor expressions

[tom-anders]

clang-tools-extra/clangd/Hover.cpp

986

Unfortunately, while CallExpr and CXXConstructExpr basically have the same API for getting Args, they're not related by a common base class.

Is there a more elegant solution than temporarily storing the Args in a SmallVector here?

[tom-anders]

(Note that this diff is stacked on D147846)

[nridge]

clang-tools-extra/clangd/Hover.cpp

986

You can use ArrayRef instead of SmallVector and avoid copying the arguments (compare process_call in InlayHintVisitor).

[tom-anders]

Use ArrayRef instead of SmallVector to avoid copy (also fix 2 typos in the comment below)

clang-tools-extra/clangd/Hover.cpp

986

Ah perfect, thanks!

[nridge]

LGTM

clang-tools-extra/clangd/Hover.cpp

 
 // If N is passed as argument to a function, fill HI.CalleeArgInfo with
 // information about that argument.
 void maybeAddCalleeArgInfo(const SelectionTree::Node *N, HoverInfo &HI,
                            const PrintingPolicy &PP) {
   const auto &OuterNode = N->outerImplicit();
   if (!OuterNode.Parent)
     return;
-  const auto *CE = OuterNode.Parent->ASTNode.get<CallExpr>();
-  if (!CE)
+
+  const FunctionDecl *FD = nullptr;
+  llvm::SmallVector<const Expr*> Args;
+
+  if (const auto *CE = OuterNode.Parent->ASTNode.get<CallExpr>()) {
+    FD = CE->getDirectCallee();
+    Args = {CE->arg_begin(), CE->arg_end()};
+  } else if (const auto *CE =
+                 OuterNode.Parent->ASTNode.get<CXXConstructExpr>()) {
+    FD = CE->getConstructor();
+    Args = {CE->arg_begin(), CE->arg_end()};
+  }
+  if (!FD)
     return;
-  const FunctionDecl *FD = CE->getDirectCallee();
+
   // For non-function-call-like operatators (e.g. operator+, operator<<) it's
   // not immediattely obvious what the "passed as" would refer to and, given
   // fixed function signature, the value would be very low anyway, so we choose
   // to not support that.
   // Both variadic functions and operator() (especially relevant for lambdas)
   // should be supported in the future.
   if (!FD || FD->isOverloadedOperator() || FD->isVariadic())
     return;
 
   HoverInfo::PassType PassType;
 
   auto Parameters = resolveForwardingParameters(FD);
 
   // Find argument index for N.
-  for (unsigned I = 0; I < CE->getNumArgs() && I < Parameters.size(); ++I) {
-    if (CE->getArg(I) != OuterNode.ASTNode.get<Expr>())
+  for (unsigned I = 0; I < Args.size() && I < Parameters.size(); ++I) {
+    if (Args[I] != OuterNode.ASTNode.get<Expr>())
       continue;
 
     // Extract matching argument from function declaration.
     if (const ParmVarDecl *PVD = Parameters[I]) {
       HI.CalleeArgInfo.emplace(toHoverInfoParam(PVD, PP));
       if (N == &OuterNode)
         PassType.PassBy = getPassMode(PVD->getType());
     }

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

class Foo final {})cpp";
             HI.LocalScope = "main::";
             HI.Value = "0";
             HI.Type = "int";
             HI.CalleeArgInfo.emplace();
             HI.CalleeArgInfo->Name = "arg";
             HI.CalleeArgInfo->Type = "const float &";
             HI.CallPassType = HoverInfo::PassType{PassMode::Value, true};
           }},
+      {
+          R"cpp(
+          struct Foo {
+            explicit Foo(const float& arg) {}
+          };
+          int main() {
+            int a = 0;
+            Foo foo([[^a]]);
+          }
+          )cpp",
+          [](HoverInfo &HI) {
+            HI.Name = "a";
+            HI.Kind = index::SymbolKind::Variable;
+            HI.NamespaceScope = "";
+            HI.Definition = "int a = 0";
+            HI.LocalScope = "main::";
+            HI.Value = "0";
+            HI.Type = "int";
+            HI.CalleeArgInfo.emplace();
+            HI.CalleeArgInfo->Name = "arg";
+            HI.CalleeArgInfo->Type = "const float &";
+            HI.CallPassType = HoverInfo::PassType{PassMode::Value, true};
+          }},
       {// Literal passed to function call
        R"cpp(
           void fun(int arg_a, const int &arg_b) {};
           void code() {
             int a = 1;
             fun(a, [[^2]]);
           }
           )cpp",

 class Base {};
 class Derived : public Base {};
 class CustomClass {
  public:
   CustomClass() {}
   CustomClass(const Base &x) {}
   CustomClass(int &x) {}
   CustomClass(float x) {}
+  CustomClass(int x, int y) {}
 };
 
 void int_by_ref(int &x) {}
 void int_by_const_ref(const int &x) {}
 void int_by_value(int x) {}
 void base_by_ref(Base &x) {}
 void base_by_const_ref(const Base &x) {}
 void base_by_value(Base x) {}
bool Converted;
       {"base_by_ref([[^base]]);", PassMode::Ref, false},
       {"base_by_const_ref([[^base]]);", PassMode::ConstRef, false},
       {"base_by_const_ref([[^base_const_ref]]);", PassMode::ConstRef, false},
       {"base_by_value([[^base]]);", PassMode::Value, false},
       {"base_by_value([[^base_const_ref]]);", PassMode::Value, false},
       {"base_by_ref([[^derived]]);", PassMode::Ref, false},
       {"base_by_const_ref([[^derived]]);", PassMode::ConstRef, false},
       {"base_by_value([[^derived]]);", PassMode::Value, false},
+      // Custom class constructor tests
+      {"CustomClass c1([[^base]]);", PassMode::ConstRef, false},
+      {"auto c2 = new CustomClass([[^base]]);", PassMode::ConstRef, false},
+      {"CustomClass c3([[^int_x]]);", PassMode::Ref, false},
+      {"CustomClass c3(int_x, [[^int_x]]);", PassMode::Value, false},
       // Converted tests
       {"float_by_value([[^int_x]]);", PassMode::Value, true},
       {"float_by_value([[^int_ref]]);", PassMode::Value, true},
       {"float_by_value([[^int_const_ref]]);", PassMode::Value, true},
       {"float_by_value([[^123.0f]]);", PassMode::Value, false},
       {"float_by_value([[^123]]);", PassMode::Value, true},
       {"custom_by_value([[^int_x]]);", PassMode::Ref, true},
       {"custom_by_value([[^float_x]]);", PassMode::Value, true},