[PATCH] D58292: Add support for importing ChooseExpr AST nodes.

[Tom Roeder via Phabricator via cfe-commits]

tmroeder added inline comments.


================
Comment at: lib/AST/ASTImporter.cpp:6160
+  // condition-dependent.
+  bool CondIsTrue = false;
+  if (!E->isConditionDependent())
----------------
aaron.ballman wrote:
> a_sidorin wrote:
> > aaron.ballman wrote:
> > > `bool CondIsTrue = E->isConditionDependent() ? false : E->isConditionTrue();`
> > `bool CondIsTrue = E->isConditionDependent() && E->isConditionTrue();`?
> I like that even better than my suggestion. :-)
Wait, this doesn't have the same truth table as my original code.

let `CD = E->isConditionDependent()`
let `CT = E->isConditionTrue()`

in

```
bool CondIsTrue = false;
if (!CD)
  CondIsTrue = CT;
```

has the table for `CondIsTrue`:

| `CD` | `CT` |  `CondIsTrue` |
| T | T | F |
| T | F | F |
| F | T | T |
| F | F | F |
i.e., if CD is true, then CondIsTrue is always false. Otherwise, it's the value of CT.

The suggested line has the truth table

| `CD` | `CT` |  `CondIsTrue` |
| T | T | T |
| T | F | F |
| F | T | F |
| F | F | F |

That is, the effect of CD is swapped.

Aaron's suggestion matches my original table. I based my code on include/clang/AST/Expr.h line 4032, which asserts !isConditionDependent() in the implementation of isConditionTrue.

I realized this after I "fixed" my comment to match the implementation change. Am I missing something? Or is the assertion in Expr.h wrong? I think this should be

```
bool CondIsTrue = !E->isConditionDependent() && E->isConditionTrue();
```

I've changed my code to that and reverted the comment change.


Repository:
  rC Clang

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D58292/new/

https://reviews.llvm.org/D58292