[clang] [CFG] Add a BuildOption to consider default branch of switch on covered enumerations. (PR #161345)

[Balazs Benics via cfe-commits]

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@@ -93,6 +93,158 @@ TEST(CFG, DependantBaseAddImplicitDtors) {
                 .getStatus());
 }
 
+TEST(CFG, SwitchCoveredEnumNoDefault) {
+  const char *Code = R"(
+    enum class E {E1, E2};
+    int f(E e) {
+      switch(e) {
+        case E::E1:
+          return 1;
+        case E::E2:
+          return 2;
+      }
+      return 0;
+    }
+  )";
+  CFG::BuildOptions Options;
+  Options.SwitchKeepDefaultCoveredEnum = true;
+  BuildResult B = BuildCFG(Code, Options);
+  EXPECT_EQ(BuildResult::BuiltCFG, B.getStatus());
+
+  // [B5 (ENTRY)]
+  //   Succs (1): B2
+  //
+  // [B1]
+  //   1: 0
+  //   2: return [B1.1];
+  //   Preds (1): B2
+  //   Succs (1): B0
+  //
+  // [B2]
+  //   1: e (ImplicitCastExpr, LValueToRValue, E)
+  //   T: switch [B2.1]
+  //   Preds (1): B5
+  //   Succs (3): B3 B4 B1
+  //
+  // [B3]
+  //  case E::E2:
+  //   1: 2
+  //   2: return [B3.1];
+  //   Preds (1): B2
+  //   Succs (1): B0
+  //
+  // [B4]
+  //  case E::E1:
+  //   1: 1
+  //   2: return [B4.1];
+  //   Preds (1): B2
+  //   Succs (1): B0
+  //
+  // [B0 (EXIT)]
+  //   Preds (3): B1 B3 B4
+
+  const auto &Entry = B.getCFG()->getEntry();
+  EXPECT_EQ(1u, Entry.succ_size());
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steakhal wrote:

I'd vote for using switching to using `ASSERT_*` and leave it like that.

https://github.com/llvm/llvm-project/pull/161345