[cfe-dev] Detect if a CXXConstructExpr is implicit

[Keane, Erich via cfe-dev]

If you look at the AST for the record decl, there is a bunch of flags in the DefinitionData of interest:
|-CXXRecordDecl <line:1:1, line:6:1> line:1:7 referenced class A 
|definition
| |-DefinitionData empty standard_layout has_user_declared_ctor 
| |can_const_default_init
| | |-DefaultConstructor exists non_trivial user_provided 
| | |defaulted_is_constexpr -CopyConstructor non_trivial user_declared 
| | |has_const_param implicit_has_const_param -MoveConstructor 
| | |-CopyAssignment trivial has_const_param needs_implicit 
| | |implicit_has_const_param -MoveAssignment

See "user_provided" and "user_declared".  I'm not sure what the difference between those two is however.

-----Original Message-----
From: cfe-dev [mailto:cfe-dev-bounces at lists.llvm.org] On Behalf Of Loïc Joly via cfe-dev
Sent: Tuesday, February 12, 2019 8:44 AM
To: cfe-dev at lists.llvm.org
Subject: [cfe-dev] Detect if a CXXConstructExpr is implicit

In the following code:

https://godbolt.org/z/czpHOf

classA{
public:
    A();
    A(A const&a);
    A(inti);
};

voidf(A a);

voidg() {
   A a;
   f(a); // 1
   f(2); // 2
}

The generated AST contains nodes about object construction that are implicit (the copy constructor for 1, the conversion then the copy constructor for 2).

     |-CallExpr <line:12:5, col:8> 'void'
     | |-ImplicitCastExpr <col:5> 'void (*)(A)' <FunctionToPointerDecay>
     | | `-DeclRefExpr <col:5> 'void (A)' lvalue Function 0x55c42589b208 'f' 'void (A)'
     | `-CXXConstructExpr <col:7> 'A' 'void (const A &)'
     |   `-ImplicitCastExpr <col:7> 'const A' lvalue <NoOp>
     |     `-DeclRefExpr <col:7> 'A' lvalue Var 0x55c42589b3c8 'a' 'A'
     `-ExprWithCleanups <line:13:5, col:8> 'void'
       `-CallExpr <col:5, col:8> 'void'
         |-ImplicitCastExpr <col:5> 'void (*)(A)' <FunctionToPointerDecay>
         | `-DeclRefExpr <col:5> 'void (A)' lvalue Function
0x55c42589b208 'f' 'void (A)'
         `-CXXConstructExpr <col:7> 'A' 'void (const A &)' elidable
           `-MaterializeTemporaryExpr <col:7> 'const A' lvalue
             `-ImplicitCastExpr <col:7> 'const A' <NoOp>
               `-ImplicitCastExpr <col:7> 'A' <ConstructorConversion>
                 `-CXXConstructExpr <col:7> 'A' 'void (int)'
                   `-IntegerLiteral <col:7> 'int' 2

Do you know if there is a way to detect that these constructions are implicit (as opposed to constructions written as the type name followed by initialization?)

Thank you!

---
Loïc Joly



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