Validation of dependent expressions

Clang Frontend
1

Hi,

I've started some work on skipping validation of expressions that have
dependent types and/or values. Am I doing it right?

Sebastian

validation.patch (7.66 KB)

2

Yes, you're on the right track. A few meta-comments:

   1) Whenever you have an expression 'E', prefer E->isTypeDependent() to E->getType()->isDependentType(). I think you're doing that already.

   2) In addition to updating Sema's type checking for value-dependent and type-dependent expressions, we also need to propagate those dependencies by updating the *Expr nodes themselves compute value- and type-dependence. For example, while updating the checking for array subscripting, we should also update ArraySubscriptExpr's constructor to accept (or compute) value- and type-dependence of the expression. For example, CallExpr has been updated to do this, and it uses

CallExpr::CallExpr(ASTContext& C, StmtClass SC, Expr *fn, Expr **args,
                    unsigned numargs, QualType t, SourceLocation rparenloc)
   : Expr(SC, t,
          fn->isTypeDependent() || hasAnyTypeDependentArguments(args, numargs),
          fn->isValueDependent() || hasAnyValueDependentArguments(args,numargs)),
     NumArgs(numargs) {

There's a big FIXME in the Expr class that will be addressed once *all* Expr nodes properly compute their type/value-dependence:

   // FIXME: Eventually, this constructor should go away and we should
   // require every subclass to provide type/value-dependence
   // information.
   Expr(StmtClass SC, QualType T)
     : Stmt(SC), TypeDependent(false), ValueDependent(false) {
     setType(T);
   }

Thanks for working on this!

  - Doug