Add tests for template instantiation

[kunaltyagi]

Required for template heavy library like PCL

Currently fails to detect function template instantiation

@divmadan help please 😄

[diivm]

File:

template <typename T>
struct AStruct { T value; };

template <typename T>
class AClass { const T privateValue; };

template <class T>
T aFunction(T&& aValue) { return aValue; }

template
struct AStruct<int>;

template
class AClass<char>;

template
bool aFunction<bool>(bool&&);

AST dump:

test.cpp:14:7: warning: class 'AClass<char>' does not declare any constructor to initialize its non-modifiable members
class AClass<char>;
      ^
test.cpp:14:7: note: in instantiation of template class 'AClass<char>' requested here
test.cpp:5:24: note: const member 'privateValue' will never be initialized
class AClass { const T privateValue; };
                       ^
TranslationUnitDecl 0x559b7f467068 <<invalid sloc>> <invalid sloc>
|-TypedefDecl 0x559b7f467948 <<invalid sloc>> <invalid sloc> implicit __int128_t '__int128'
| `-BuiltinType 0x559b7f467600 '__int128'
|-TypedefDecl 0x559b7f4679b8 <<invalid sloc>> <invalid sloc> implicit __uint128_t 'unsigned __int128'
| `-BuiltinType 0x559b7f467620 'unsigned __int128'
|-TypedefDecl 0x559b7f467d40 <<invalid sloc>> <invalid sloc> implicit __NSConstantString '__NSConstantString_tag'
| `-RecordType 0x559b7f467aa0 '__NSConstantString_tag'
|   `-CXXRecord 0x559b7f467a10 '__NSConstantString_tag'
|-TypedefDecl 0x559b7f467de8 <<invalid sloc>> <invalid sloc> implicit __builtin_ms_va_list 'char *'
| `-PointerType 0x559b7f467da0 'char *'
|   `-BuiltinType 0x559b7f467100 'char'
|-TypedefDecl 0x559b7f4a5ce0 <<invalid sloc>> <invalid sloc> implicit __builtin_va_list '__va_list_tag [1]'
| `-ConstantArrayType 0x559b7f4a5c80 '__va_list_tag [1]' 1 
|   `-RecordType 0x559b7f467ed0 '__va_list_tag'
|     `-CXXRecord 0x559b7f467e40 '__va_list_tag'
|-ClassTemplateDecl 0x559b7f4a5ea0 <test.cpp:1:1, line:2:27> col:8 AStruct
| |-TemplateTypeParmDecl 0x559b7f4a5d38 <line:1:11, col:20> col:20 referenced typename depth 0 index 0 T
| |-CXXRecordDecl 0x559b7f4a5e10 <line:2:1, col:27> col:8 struct AStruct definition
| | |-DefinitionData aggregate standard_layout trivially_copyable trivial
| | | |-DefaultConstructor exists trivial needs_implicit
| | | |-CopyConstructor simple trivial has_const_param needs_implicit implicit_has_const_param
| | | |-MoveConstructor exists simple trivial needs_implicit
| | | |-CopyAssignment trivial has_const_param needs_implicit implicit_has_const_param
| | | |-MoveAssignment exists simple trivial needs_implicit
| | | `-Destructor simple irrelevant trivial needs_implicit
| | |-CXXRecordDecl 0x559b7f4a6108 <col:1, col:8> col:8 implicit struct AStruct
| | `-FieldDecl 0x559b7f4a61a8 <col:18, col:20> col:20 value 'T'
| `-ClassTemplateSpecialization 0x559b7f4a6a78 'AStruct'
|-ClassTemplateDecl 0x559b7f4a6340 <line:4:1, line:5:38> col:7 AClass
| |-TemplateTypeParmDecl 0x559b7f4a6210 <line:4:11, col:20> col:20 referenced typename depth 0 index 0 T
| |-CXXRecordDecl 0x559b7f4a62b0 <line:5:1, col:38> col:7 class AClass definition
| | |-DefinitionData standard_layout trivially_copyable trivial
| | | |-DefaultConstructor exists trivial needs_implicit
| | | |-CopyConstructor simple trivial has_const_param needs_implicit implicit_has_const_param
| | | |-MoveConstructor exists simple trivial needs_implicit
| | | |-CopyAssignment trivial has_const_param needs_implicit implicit_has_const_param
| | | |-MoveAssignment exists trivial needs_implicit
| | | `-Destructor simple irrelevant trivial needs_implicit
| | |-CXXRecordDecl 0x559b7f4a65a8 <col:1, col:7> col:7 implicit class AClass
| | `-FieldDecl 0x559b7f4a6648 <col:16, col:24> col:24 privateValue 'const T'
| `-ClassTemplateSpecialization 0x559b7f4d54a8 'AClass'
|-FunctionTemplateDecl 0x559b7f4a6970 <line:7:1, line:8:42> col:3 aFunction
| |-TemplateTypeParmDecl 0x559b7f4a66b0 <line:7:11, col:17> col:17 referenced class depth 0 index 0 T
| |-FunctionDecl 0x559b7f4a68d0 <line:8:1, col:42> col:3 aFunction 'T (T &&)'
| | |-ParmVarDecl 0x559b7f4a67c0 <col:13, col:17> col:17 referenced aValue 'T &&'
| | `-CompoundStmt 0x559b7f4a6a48 <col:25, col:42>
| |   `-ReturnStmt 0x559b7f4a6a38 <col:27, col:34>
| |     `-DeclRefExpr 0x559b7f4a6a18 <col:34> 'T' lvalue ParmVar 0x559b7f4a67c0 'aValue' 'T &&'
| `-FunctionDecl 0x559b7f4d5bb8 <col:1, col:42> col:3 aFunction 'bool (bool &&)'
|   |-TemplateArgument type 'bool'
|   |-ParmVarDecl 0x559b7f4d5b28 <col:13, col:17> col:17 used aValue 'bool &&'
|   `-CompoundStmt 0x559b7f4d5d00 <col:25, col:42>
|     `-ReturnStmt 0x559b7f4d5cf0 <col:27, col:34>
|       `-ImplicitCastExpr 0x559b7f4d5cd8 <col:34> 'bool':'bool' <LValueToRValue>
|         `-DeclRefExpr 0x559b7f4d5cb8 <col:34> 'bool':'bool' lvalue ParmVar 0x559b7f4d5b28 'aValue' 'bool &&'
|-ClassTemplateSpecializationDecl 0x559b7f4a6a78 <line:10:1, line:11:19> col:8 struct AStruct definition
| |-DefinitionData pass_in_registers aggregate standard_layout trivially_copyable pod trivial literal
| | |-DefaultConstructor exists trivial needs_implicit
| | |-CopyConstructor simple trivial has_const_param needs_implicit implicit_has_const_param
| | |-MoveConstructor exists simple trivial needs_implicit
| | |-CopyAssignment trivial has_const_param needs_implicit implicit_has_const_param
| | |-MoveAssignment exists simple trivial needs_implicit
| | `-Destructor simple irrelevant trivial needs_implicit
| |-TemplateArgument type 'int'
| |-CXXRecordDecl 0x559b7f4d5358 prev 0x559b7f4a6a78 <line:2:1, col:8> col:8 implicit struct AStruct
| `-FieldDecl 0x559b7f4d5430 <col:18, col:20> col:20 value 'int':'int'
`-ClassTemplateSpecializationDecl 0x559b7f4d54a8 <line:13:1, line:14:18> col:7 class AClass definition
  |-DefinitionData pass_in_registers standard_layout trivially_copyable trivial literal
  | |-DefaultConstructor exists trivial needs_implicit
  | |-CopyConstructor simple trivial has_const_param needs_implicit implicit_has_const_param
  | |-MoveConstructor exists simple trivial needs_implicit
  | |-CopyAssignment trivial has_const_param needs_implicit implicit_has_const_param
  | |-MoveAssignment exists trivial needs_implicit
  | `-Destructor simple irrelevant trivial needs_implicit
  |-TemplateArgument type 'char'
  |-CXXRecordDecl 0x559b7f4d56b0 prev 0x559b7f4d54a8 <line:5:1, col:7> col:7 implicit class AClass
  `-FieldDecl 0x559b7f4d5780 <col:16, col:24> col:24 privateValue 'const char':'const char'
1 warning generated.

[diivm]

Let's merge #6 first and then solve this issue.