Force computation of discriminators when dumping for non-debugging purposes

Some testing mechanisms depend on having closure discriminators
pre-computed when dumping the AST. When not dumping to either the
standard error or debugger output streams, trigger computation of
closure discriminators prior to dumping them.

Author: DougGregor

lib/AST/ASTDumper.cpp

@@ -1388,6 +1388,12 @@ void swift::printContext(raw_ostream &os, DeclContext *dc) {
       PrintWithColorRAII(os, DiscriminatorColor)
         << "autoclosure discriminator=";
     }
+
+    // If we aren't printing to standard error or the debugger output stream,
+    // this client expects to see the computed discriminator. Compute it now.
+    if (&os != &llvm::errs() && &os != &llvm::dbgs())
+      (void)ACE->getDiscriminator();
+
     PrintWithColorRAII(os, DiscriminatorColor) << ACE->getRawDiscriminator();
     break;
   }
@@ -2554,6 +2560,12 @@ class PrintExpr : public ExprVisitor<PrintExpr> {
 
   llvm::raw_ostream &printClosure(AbstractClosureExpr *E, char const *name) {
     printCommon(E, name);
+
+    // If we aren't printing to standard error or the debugger output stream,
+    // this client expects to see the computed discriminator. Compute it now.
+    if (&OS != &llvm::errs() && &OS != &llvm::dbgs())
+      (void)E->getDiscriminator();
+
     PrintWithColorRAII(OS, DiscriminatorColor)
       << " discriminator=" << E->getRawDiscriminator();