Hello, I'm trying to figure it out how dmd compiler is working and using his parser and tools for my little utility, I learned how to parse a file and working with parsed data via visitor, I wrote this:
> class CollectVisitor : TransitiveVisitor {
>     override void visit(ASTBase.Import imp) {
>         writeln();
>         writeln("visit import");
>     }
> 
>     override void visit(ASTBase.StructDeclaration d) {
>         writeln();
>         writeln("visit struct");
>     }
> 
>     override void visit(ASTBase.UserAttributeDeclaration d) {
>         writeln();
>         writeln("visit attribute");
>         writeln("attributes:");
> 
>         foreach (a; *d.atts) {
>             // How can I here read data from a?
>         }
> 
>         writeln("declarations:");
>         foreach (s; *d.decl) {
>             writeln("  ", s.ident.toString());
>         }
>     }
> }

I'm trying to parse this file:
> @Tag
> @Tag1
> struct A {
>     void greet() {
>         writeln("Hello world!");
>     }
> }
> 
> @Tag
> struct B {
>     void greet() {
>         writeln("Hello world!");
>     }
> }

I can parse it, and read some data from structs (so far only name), but how can I retrieve some info from UDAs? e.g. name? atts is array of expressions, but I don't understand how retrieve something from expression (I need name of attribute and its parameters).

I understood, I need to read the op field from expression and cast to needed expression type

On 2017-10-08 10:12, Andrey wrote:

> I can parse it, and read some data from structs (so far only name), but how can I retrieve some info from UDAs? e.g. name? atts is array of expressions, but I don't understand how retrieve something from expression (I need name of attribute and its parameters).

You can have a look here [1]. This looks for the @selector("foo") UDA on a method declaration, extracts the string "foo" and stores it for later processing.

[1] https://github.com/dlang/dmd/blob/master/src/ddmd/objc.d#L199

-- 
/Jacob Carlborg