[LLDB][ClangExpression] Fix initialization of static enum alias members

`IntegerLiteral::Create` operates on integer types. For that reason
when we parse DWARF into an AST, when we encounter a constant
initialized enum member variable, we try to determine the underlying
integer type before creating the `IntegerLiteral`. However, we
currently don't desugar the type and for enum typedefs
`dyn_cast<EnumType>` fails. In debug builds this triggers following
assert:

```
Assertion failed: (type->isIntegerType() && "Illegal type in IntegerLiteral"), function IntegerLiteral, file Expr.cpp, line 892
```

This patch turns the `dyn_cast<EnumType>` into a `getAs<EnumType>`
which `dyn_cast`s the canonical type, allowing us to get to the
underlying integer type.

**Testing**

* API test
* Manual repro is fixed

Differential Revision: https://reviews.llvm.org/D130213

2 files changed, 19 insertions, 0 deletions

diff --git a/lldb/test/API/lang/cpp/const_static_integral_member/TestConstStaticIntegralMember.py b/lldb/test/API/lang/cpp/const_static_integral_member/TestConstStaticIntegralMember.py
index c2bf1fe..09345b9 100644
--- a/lldb/test/API/lang/cpp/const_static_integral_member/TestConstStaticIntegralMember.py
+++ b/lldb/test/API/lang/cpp/const_static_integral_member/TestConstStaticIntegralMember.py
@@ -66,6 +66,12 @@ class TestCase(TestBase):
         self.expect_expr("A::scoped_ll_enum_val_neg", result_value="case0")
         self.expect_expr("A::scoped_ll_enum_val", result_value="case2")
 
+        # Test an aliased enum with fixed underlying type.
+        self.expect_expr("ClassWithEnumAlias::enum_alias",
+                         result_value="scoped_enum_case2")
+        self.expect_expr("ClassWithEnumAlias::enum_alias_alias",
+                         result_value="scoped_enum_case1")
+
         # Test taking address.
         if lldbplatformutil.getPlatform() == "windows":
             # On Windows data members without the out-of-class definitions still have
diff --git a/lldb/test/API/lang/cpp/const_static_integral_member/main.cpp b/lldb/test/API/lang/cpp/const_static_integral_member/main.cpp
index 9762424..b262513 100644
--- a/lldb/test/API/lang/cpp/const_static_integral_member/main.cpp
+++ b/lldb/test/API/lang/cpp/const_static_integral_member/main.cpp
@@ -69,6 +69,15 @@ struct ClassWithConstexprs {
   constexpr static ScopedEnum scoped_enum_val = ScopedEnum::scoped_enum_case2;
 } cwc;
 
+struct ClassWithEnumAlias {
+  using EnumAlias = ScopedEnum;
+  static constexpr EnumAlias enum_alias = ScopedEnum::scoped_enum_case2;
+
+  using EnumAliasAlias = EnumAlias;
+  static constexpr EnumAliasAlias enum_alias_alias =
+      ScopedEnum::scoped_enum_case1;
+};
+
 int main() {
   A a;
 
@@ -98,5 +107,9 @@ int main() {
   se = A::invalid_scoped_enum_val;
   ScopedCharEnum sce = A::scoped_char_enum_val;
   ScopedLongLongEnum sle = A::scoped_ll_enum_val;
+
+  auto enum_alias_val = ClassWithEnumAlias::enum_alias;
+  auto enum_alias_alias_val = ClassWithEnumAlias::enum_alias_alias;
+
   return 0; // break here
 }