dredd doesn't mutate some `CastExpr` under `--no-mutation-opts` option

[JonathanFoo0523]

Applying dredd to

int main() {
  unsigned int x = 1;
}

mutate the declaration statement to

 unsigned int x = __dredd_replace_expr_unsigned_int(__dredd_replace_expr_int(1, 0), 6);

with the following AST.

FunctionDecl 0x55d773f60890 </home/ubuntu/dredd/examples/simple/cast.cc:1:1, line:3:1> line:1:5 main 'int ()'
  `-CompoundStmt 0x55d773f60a80 <col:12, line:3:1>
    `-DeclStmt 0x55d773f60a68 <line:2:3, col:21>
      `-VarDecl 0x55d773f609c8 <col:3, col:20> col:16 x 'unsigned int' cinit
        `-ImplicitCastExpr 0x55d773f60a50 <col:20> 'unsigned int' <IntegralCast>
          `-IntegerLiteral 0x55d773f60a30 <col:20> 'int' 1

Am I right to assume that __dredd_replace_expr_int is the result of mutation on IntegerLiteral, and __dredd_replace_expr_unsigned_int is the result of mutation on ImplicitCastExpr?

If that the case, consider another example with similar AST:

#include <initializer_list>
class foo {
public:
  foo(std::initializer_list<unsigned>) {}
};

int main() { 
  foo{2};
}

which mutate the one line in foo{2} to

foo{static_cast<unsigned int>(__dredd_replace_expr_int(2, 0))}

with the following AST:

FunctionDecl 0x55e2836e16a0 <line:7:1, line:9:1> line:7:5 main 'int ()'
  `-CompoundStmt 0x55e2836e2ce8 <col:12, line:9:1>
    `-ExprWithCleanups 0x55e2836e2cd0 <line:8:3, col:8> 'foo':'foo'
      `-CXXTemporaryObjectExpr 0x55e2836e2ba8 <col:3, col:8> 'foo':'foo' 'void (std::initializer_list<unsigned int>)' list std::initializer_list
        `-CXXStdInitializerListExpr 0x55e2836e2988 <col:6, col:8> 'std::initializer_list<unsigned int>':'std::initializer_list<unsigned int>'
          `-MaterializeTemporaryExpr 0x55e2836e2970 <col:6, col:8> 'const unsigned int[1]' xvalue
            `-InitListExpr 0x55e2836e1ce8 <col:6, col:8> 'const unsigned int[1]'
              `-ImplicitCastExpr 0x55e2836e1d30 <col:7> 'const unsigned int' <IntegralCast>
                `-IntegerLiteral 0x55e2836e1800 <col:7> 'int' 2

So, __dredd_replace_expr_int is the result of mutation on IntegerLiteral as previous. Why isn't there __dredd_replace_expr_unsigned_int acting on ImplicitCastExpr?

[JonathanFoo0523]

Seems like Dredd doesn't mutate ImplicitCastExpr in the second example because it is not a supported type and thus fail the check here. More specifically, it is not a clang::BuiltinType for some reason.

[afd]

With Dredd's new --show-ast-node-types flag, together with --dump-ast, you'll be able to see exactly which node each mutator function corresponds to. Would that help get to the bottom of this?