Problem using ast matchers macros

Clang Frontend
1

I’m trying to implement an ast matcher for the IHD (hidden variable deletion) operator. For this purpose, i also define two matchers using the ast macros. The code is as follows:

namespace clang{
namespace ast_matchers{
using namespace clang::ast_matchers::internal;

// Checks that two FieldDecl nodes have the same type
AST_MATCHER_P(FieldDecl, SameType, FieldDecl, f)
{
return Node.getType() == f.getType();
}

// Checks that two FieldDecl nodes have the same name
AST_MATCHER_P(FieldDecl, SameName, FieldDecl, f)
{
return Node.getName() == f.getName();
}

}
}

And the code for the IHD operator is:

DeclarationMatcher IHD__Matcher = recordDecl(
has(
fieldDecl().bind(“IHD”)
),
isDerivedFrom(
SameName(
SameType(
recordDecl(
has(
fieldDecl()
)
)
)
)
)
);

The problem is that when i compile i get the following errors:

clang++ -I/usr/local/include -D_DEBUG -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -g -fvisibility-inlines-hidden -fno-exceptions -fno-rtti -fPIC -Woverloaded-virtual -Wcast-qual -fno-rtti -c -o IHD_operator.o IHD_operator.cpp
IHD_operator.cpp:83:6: error: no matching function for call to ‘SameType’
SameType(
^~~~~~~~
IHD_operator.cpp:39:28: note: candidate function not viable: no known conversion from ‘clang::ast_matchers::internal::BindableMatcherclang::Decl’ to
‘const clang::FieldDecl’ for 1st argument
AST_MATCHER_P(FieldDecl, SameType, FieldDecl, f)
^
/usr/local/include/clang/ASTMatchers/ASTMatchersMacros.h:86:32: note: expanded from macro ‘AST_MATCHER_P’
AST_MATCHER_P_OVERLOAD(Type, DefineMatcher, ParamType, Param, 0)
^
/usr/local/include/clang/ASTMatchers/ASTMatchersMacros.h:104:34: note: expanded from macro ‘AST_MATCHER_P_OVERLOAD’
inline internal::Matcher DefineMatcher(const ParamType &Param) {
^
1 error generated.
make: *** [IHD_operator.o] Error 1

I don’t know why is trying to make a conversion to FieldDecl from Decl if it is supose to be receiving a FieldDecl type param.

2

The source of the failure is where you have SameType(recordDecl(…)). You’ll notice in the reference that recordDecl() returns a Matcher. So your SameType() matcher is going to receive a ‘Decl’ as input. You’ll need to explicitly change this into a FieldDecl. I’m afraid I don’t know exactly what you’re trying to match or what IHD is so I can’t tell if there’s a more fundamental error here.

3

Actually, the problem is that you’re passing a matcher as argument, while you’ve defined your matchers to accept FieldDecl (the 3rd argument for the AST_MATCHER_P macro) - but the compiler already told you this.

So I don’t really see what you’re confused about. For that matter, nor can I really tell what you’re trying to do in your matcher expression… What is it that you’re trying to express here?

4

You can look at the equalsBoundNode matcher to get an idea of how something like you are trying to do can be implemented.