[clangd] PopulateSwitch: disable on dependent enums.

[adamcz]

Summary

If the enum is a dependent type, we would crash somewhere in
getIntWidth(). -Wswitch diagnostic doesn't work on dependent enums
either.

[hokein]

thanks.

clang-tools-extra/clangd/refactor/tweaks/PopulateSwitch.cpp

bool PopulateSwitch::prepare(const Selection &Sel) {
   // Ignore implicit casts, since enums implicitly cast to integer types.
   Cond = Cond->IgnoreParenImpCasts();
 
   EnumT = Cond->getType()->getAsAdjusted<EnumType>();
   if (!EnumT)
     return false;
 
   EnumD = EnumT->getDecl();
-  if (!EnumD)
+  if (!EnumD || EnumD->isDependentType())
     return false;
 
   // We trigger if there are any values in the enum that aren't covered by the
   // switch.
 
   ASTContext &Ctx = Sel.AST->getASTContext();
 
   unsigned EnumIntWidth = Ctx.getIntWidth(QualType(EnumT, 0));

clang-tools-extra/clangd/unittests/TweakTests.cpp

Case Cases[]{
           R""(enum Enum {A,B,b=B}; switch (A) {case A:case B:break;})"",
       },
       {
           // Duplicated constant names all in switch
           Function,
           R""(enum Enum {A,B,b=B}; ^switch (A) {case A:case B:break;})"",
           "unavailable",
       },
+      {
+          // Enum is dependent type
+          File,
+          R""(template<typename T> void f() {enum Enum {A}; ^switch (A) {}})"",
+          "unavailable",
+      },
   };
 
   for (const auto &Case : Cases) {
     Context = Case.Context;
     EXPECT_EQ(apply(Case.TestSource), Case.ExpectedSource);
   }
 }
 
 } // namespace
 } // namespace clangd
 } // namespace clang