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[ADT] Add DefaultUnreachable("msg") to StringSwitch #161976

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Merged
merged 2 commits into from
Oct 5, 2025
Merged

[ADT] Add DefaultUnreachable("msg") to StringSwitch #161976

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[ADT] Add `DefaultUnreachable("msg")` to StringSwitch
kuhar Oct 4, 2025
7422e8a
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kuhar Oct 4, 2025
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12 changes: 9 additions & 3 deletions llvm/include/llvm/ADT/StringSwitch.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#define LLVM_ADT_STRINGSWITCH_H

#include "llvm/ADT/StringRef.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
#include <cstring>
#include <optional>
Expand Down Expand Up @@ -180,11 +181,16 @@ class StringSwitch {
return Value;
}

[[nodiscard]] operator R() {
assert(Result && "Fell off the end of a string-switch");
return std::move(*Result);
/// Declare default as unreachable, making sure that all cases were handled.
[[nodiscard]] R DefaultUnreachable(
const char *Message = "Fell off the end of a string-switch") {
if (Result)
return std::move(*Result);
llvm_unreachable(Message);
}

[[nodiscard]] operator R() { return DefaultUnreachable(); }

private:
// Returns true when `Str` matches the `S` argument, and stores the result.
bool CaseImpl(T &Value, StringLiteral S) {
Expand Down
16 changes: 16 additions & 0 deletions llvm/unittests/ADT/StringSwitchTest.cpp
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Expand Up @@ -230,3 +230,19 @@ TEST(StringSwitchTest, CasesCopies) {
"Foo", "Bar", "Baz", "Qux", Copyable{NumCopies});
EXPECT_EQ(NumCopies, 1u);
}

TEST(StringSwitchTest, DefaultUnreachable) {
auto Translate = [](StringRef S) {
return llvm::StringSwitch<int>(S)
.Case("A", 0)
.Case("B", 1)
.DefaultUnreachable("Unhandled case");
};

EXPECT_EQ(0, Translate("A"));
EXPECT_EQ(1, Translate("B"));

#if defined(GTEST_HAS_DEATH_TEST) && !defined(NDEBUG)
EXPECT_DEATH((void)Translate("C"), "Unhandled case");
#endif
}