Fix GetFunctionSignature to work for FunctionTemplateDecls (#536)

Author: aaronj0

lib/Interpreter/CppInterOp.cpp

@@ -963,20 +963,25 @@ namespace Cpp {
       return "<unknown>";
 
     auto *D = (clang::Decl *) func;
-    if (auto *FD = llvm::dyn_cast<FunctionDecl>(D)) {
-      std::string Signature;
-      raw_string_ostream SS(Signature);
-      PrintingPolicy Policy = getASTContext().getPrintingPolicy();
-      // Skip printing the body
-      Policy.TerseOutput = true;
-      Policy.FullyQualifiedName = true;
-      Policy.SuppressDefaultTemplateArgs = false;
-      FD->print(SS, Policy);
-      SS.flush();
-      return Signature;
-    }
+    clang::FunctionDecl* FD;
+
+    if (llvm::dyn_cast<FunctionDecl>(D))
+      FD = llvm::dyn_cast<FunctionDecl>(D);
+    else if (auto* FTD = llvm::dyn_cast<clang::FunctionTemplateDecl>(D))
+      FD = FTD->getTemplatedDecl();
+    else
+      return "<unknown>";
 
-    return "<unknown>";
+    std::string Signature;
+    raw_string_ostream SS(Signature);
+    PrintingPolicy Policy = getASTContext().getPrintingPolicy();
+    // Skip printing the body
+    Policy.TerseOutput = true;
+    Policy.FullyQualifiedName = true;
+    Policy.SuppressDefaultTemplateArgs = false;
+    FD->print(SS, Policy);
+    SS.flush();
+    return Signature;
   }
 
   // Internal functions that are not needed outside the library are

unittests/CppInterOp/FunctionReflectionTest.cpp

@@ -497,13 +497,17 @@ TEST(FunctionReflectionTest, GetFunctionSignature) {
   std::string code = R"(
     class C {
       void f(int i, double d, long l = 0, char ch = 'a') {}
+      template<typename T>
+      void ft(T a) {}
     };
 
     namespace N
     {
       void f(int i, double d, long l = 0, char ch = 'a') {}
     }
 
+    template<typename T>
+    void ft(T a) {}
     void f1() {}
     C f2(int i, double d, long l = 0, char ch = 'a') { return C(); }
     C *f3(int i, double d, long l = 0, char ch = 'a') { return new C(); }
@@ -515,18 +519,19 @@ TEST(FunctionReflectionTest, GetFunctionSignature) {
   GetAllSubDecls(Decls[0], Decls);
   GetAllSubDecls(Decls[1], Decls);
 
-  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[2]), "void f1()");
-  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[3]),
-            "C f2(int i, double d, long l = 0, char ch = 'a')");
+  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[2]), "void ft(T a)");
+  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[3]), "void f1()");
   EXPECT_EQ(Cpp::GetFunctionSignature(Decls[4]),
-            "C *f3(int i, double d, long l = 0, char ch = 'a')");
+            "C f2(int i, double d, long l = 0, char ch = 'a')");
   EXPECT_EQ(Cpp::GetFunctionSignature(Decls[5]),
-            "void f4(int i = 0, double d = 0., long l = 0, char ch = 'a')");
+            "C *f3(int i, double d, long l = 0, char ch = 'a')");
   EXPECT_EQ(Cpp::GetFunctionSignature(Decls[6]),
-            "<unknown>");
-  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[8]),
+            "void f4(int i = 0, double d = 0., long l = 0, char ch = 'a')");
+  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[7]), "<unknown>");
+  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[9]),
             "void C::f(int i, double d, long l = 0, char ch = 'a')");
-  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[13]),
+  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[10]), "void C::ft(T a)");
+  EXPECT_EQ(Cpp::GetFunctionSignature(Decls[15]),
             "void N::f(int i, double d, long l = 0, char ch = 'a')");
   EXPECT_EQ(Cpp::GetFunctionSignature(nullptr), "<unknown>");
 }