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Compiler Error C2783

 

The latest version of this topic can be found at Compiler Error C2783.

declaration' : could not deduce template argument for 'identifier'

The compiler cannot determine a template argument. Default arguments cannot be used to deduce a template argument.

The following sample generates C2783:

// C2783.cpp  
template<typename T1, typename T2>  
T1 f(T2) {  
   return 248;  
}  
  
int main() {  
   f(1);   // C2783  
   // try the following line instead  
   int i = f<int>(1);  
}  

C2783 can also occur when using generics:

// C2783b.cpp  
// compile with: /clr  
using namespace System;  
generic<typename T1, typename T2>   
T1 gf(T2) {  
   T1 t1 = safe_cast<T1>( Activator::CreateInstance(T1::typeid));  
   return t1;  
}  
  
ref class MyClass{};  
  
int main() {  
   int i;  
   i = gf(9);   // C2783  
  
   // OK  
   i = gf<int>(9);  
}  

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