[cfe-dev] Remove implicitly generated AST nodes by Sema

[Eli Friedman]

Expr::IgnoreImplicit() lets you easily look through implicit expressions.

-Eli


On Tue, Jun 4, 2013 at 11:56 AM, Pan, Wei <wei.pan at intel.com> wrote:

> Hi all,
>
> I am wondering if it is possible to remove all the implicitly generated
> AST nodes.
>
> For example (below), the only argument to call (1) is a "DeclRefExpr" to
> y, and the only
> argument to call (2) is a "CXXContructExpr", if ignoring nodes created by
> the initialization
> sequence for the call.
>
> Basically, I want to get the "syntactic form" Expr from an expression with
> some semantic
> analysis. Is there an existing way to do so? Or what would be a proper way
> to implement this?
>
> Thanks!
>
> Wei
>
> ------------------------------------------------------------------
>
> struct Y { };
> struct X { X(); X(Y&); };
> void foo(X);
>
> void bar(Y &y) {
>   foo(y);     // (1)
>   foo(X(y));  // (2)
> }
>
> |-CallExpr 0x2a6c790 <line:8:3, col:8> 'void'
> | |-ImplicitCastExpr 0x2a6c778 <col:3> 'void (*)(struct X)'
> <FunctionToPointerDecay>
> | | `-DeclRefExpr 0x2a6c728 <col:3> 'void (struct X)' lvalue Function
> 0x2a6c2c0 'foo' 'void (struct X)'
> | `-CXXConstructExpr 0x2a6c9f8 <col:7> 'struct X' 'void (const struct X &)
> throw()' elidable
> |   `-MaterializeTemporaryExpr 0x2a6c988 <col:7> 'const struct X' lvalue
> |     `-ImplicitCastExpr 0x2a6c970 <col:7> 'const struct X' <NoOp>
> |       `-ImplicitCastExpr 0x2a6c800 <col:7> 'struct X'
> <ConstructorConversion>
> |         `-CXXConstructExpr 0x2a6c7c8 <col:7> 'struct X' 'void (struct Y
> &)'
> |           `-DeclRefExpr 0x2a6c500 <col:7> 'struct Y' lvalue ParmVar
> 0x2a6c380 'y' 'struct Y &'
> `-CallExpr 0x2a6cb60 <line:9:3, col:11> 'void'
>   |-ImplicitCastExpr 0x2a6cb48 <col:3> 'void (*)(struct X)'
> <FunctionToPointerDecay>
>   | `-DeclRefExpr 0x2a6cb20 <col:3> 'void (struct X)' lvalue Function
> 0x2a6c2c0 'foo' 'void (struct X)'
>    `-CXXConstructExpr 0x2a6cbc8 <col:7, col:10> 'struct X' 'void (const
> struct X &) throw()' elidable
>      `-MaterializeTemporaryExpr 0x2a6cbb0 <col:7, col:10> 'const struct X'
> lvalue
>        `-ImplicitCastExpr 0x2a6cb98 <col:7, col:10> 'const struct X' <NoOp>
>          `-CXXFunctionalCastExpr 0x2a6caf8 <col:7, col:10> 'struct X'
> functional cast to struct X <ConstructorConversion>
>            `-CXXConstructExpr 0x2a6cac0 <col:7, col:10> 'struct X' 'void
> (struct Y &)'
>              `-DeclRefExpr 0x2a6ca98 <col:9> 'struct Y' lvalue ParmVar
> 0x2a6c380 'y' 'struct Y &'
>
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