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https://github.com/carbon-language/carbon-lang.git
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Jon Ross-Perkins
800e8fd55a
Also document why these are expected on `CARBON_KIND`. In
`kind_switch_test.cpp`, drop the `str` variable.
My recollection of the original discussion of `CARBON_KIND` is that it
should always have braces due to the risk of confusion for statement
interpretation, similar to a typical `if`/`else` but more subtle due to
the macro.
For example:
```
case CARBON_KIND(int n):
str << "int = " << n;
return str.TakeStr();
```
is equivalent to:
```
case CARBON_KIND(int n): {
str << "int = " << n;
}
return str.TakeStr();
```
This happens to work in context because `str` isn't scoped, but a
trivial refactoring to move `RawStringOstream str;` the first statement
of the `case` would probably have non-obvious results. For example:
```
case CARBON_KIND(int n):
RawStringOstream str; // Valid name shadowing, destructed without use.
str << "int = " << n; // Name lookup error on `n`.
return str.TakeStr();
```
55 lines
1.3 KiB
C++
55 lines
1.3 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "toolchain/base/kind_switch.h"
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#include <gtest/gtest.h>
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#include <string>
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#include <variant>
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#include "common/raw_string_ostream.h"
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namespace Carbon {
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namespace {
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TEST(KindSwitch, Variant) {
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auto f = [](std::variant<int, float, char> v) -> std::string {
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CARBON_KIND_SWITCH(v) {
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case CARBON_KIND(int n): {
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return llvm::formatv("int = {0}", n);
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}
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case CARBON_KIND(float f): {
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return llvm::formatv("float = {0}", f);
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}
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case CARBON_KIND(char c): {
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return llvm::formatv("char = {0}", c);
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}
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}
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};
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EXPECT_EQ(f(int{1}), "int = 1");
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EXPECT_EQ(f(float{2}), "float = 2.00");
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EXPECT_EQ(f(char{'h'}), "char = h");
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}
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TEST(KindSwitch, VariantUnusedValue) {
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auto f = [](std::variant<int, float> v) -> std::string {
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CARBON_KIND_SWITCH(v) {
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case CARBON_KIND(int n): {
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return llvm::formatv("int = {0}", n);
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}
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case CARBON_KIND(float _):
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// The float value is not used, we see that using `_` works.
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return "float";
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}
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};
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EXPECT_EQ(f(int{1}), "int = 1");
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EXPECT_EQ(f(float{2}), "float");
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}
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} // namespace
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} // namespace Carbon
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