[clang-tidy] Add the abseil-duration-subtraction check

Summary:
This check uses the context of a subtraction expression as well as knowledge
about the Abseil Time types, to infer the type of the second operand of some
subtraction expressions in Duration conversions. For example:

   absl::ToDoubleSeconds(duration) - foo

can become
   absl::ToDoubleSeconds(duration - absl::Seconds(foo))

This ensures that time calculations are done in the proper domain, and also
makes it easier to further deduce the types of the second operands to these
expressions.

Reviewed By: JonasToth

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D55245

1 files changed, 64 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/abseil-duration-subtraction.cpp b/clang-tools-extra/test/clang-tidy/abseil-duration-subtraction.cpp
new file mode 100644
index 00000000000..154b7d4ba76
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/abseil-duration-subtraction.cpp
@@ -0,0 +1,64 @@
+// RUN: %check_clang_tidy %s abseil-duration-subtraction %t -- -- -I %S/Inputs
+
+#include "absl/time/time.h"
+
+void f() {
+  double x;
+  absl::Duration d, d1, d2;
+
+  x = absl::ToDoubleSeconds(d) - 1.0;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleSeconds(d - absl::Seconds(1))
+  x = absl::ToDoubleSeconds(d) - absl::ToDoubleSeconds(d1);
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleSeconds(d - d1);
+  x = absl::ToDoubleSeconds(d) - 6.5 - 8.0;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleSeconds(d - absl::Seconds(6.5)) - 8.0;
+  x = absl::ToDoubleHours(d) - 1.0;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleHours(d - absl::Hours(1))
+  x = absl::ToDoubleMinutes(d) - 1;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleMinutes(d - absl::Minutes(1))
+  x = absl::ToDoubleMilliseconds(d) - 9;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleMilliseconds(d - absl::Milliseconds(9))
+  x = absl::ToDoubleMicroseconds(d) - 9;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleMicroseconds(d - absl::Microseconds(9))
+  x = absl::ToDoubleNanoseconds(d) - 42;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleNanoseconds(d - absl::Nanoseconds(42))
+
+  // We can rewrite the argument of the duration conversion
+#define THIRTY absl::Seconds(30)
+  x = absl::ToDoubleSeconds(THIRTY) - 1.0;
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleSeconds(THIRTY - absl::Seconds(1))
+#undef THIRTY
+
+  // Some other contexts
+  if (absl::ToDoubleSeconds(d) - 1.0 > 10) {}
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: if (absl::ToDoubleSeconds(d - absl::Seconds(1)) > 10) {}
+
+  // A nested occurance
+  x = absl::ToDoubleSeconds(d) - absl::ToDoubleSeconds(absl::Seconds(5));
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleSeconds(d - absl::Seconds(5))
+  x = absl::ToDoubleSeconds(d) - absl::ToDoubleSeconds(absl::Seconds(absl::ToDoubleSeconds(d1)));
+  // CHECK-MESSAGES: [[@LINE-1]]:7: warning: perform subtraction in the duration domain [abseil-duration-subtraction]
+  // CHECK-FIXES: absl::ToDoubleSeconds(d - absl::Seconds(absl::ToDoubleSeconds(d1)))
+
+  // These should not match
+  x = 5 - 6;
+  x = 4 - absl::ToDoubleSeconds(d) - 6.5 - 8.0;
+  x = absl::ToDoubleSeconds(d) + 1.0;
+  x = absl::ToDoubleSeconds(d) * 1.0;
+  x = absl::ToDoubleSeconds(d) / 1.0;
+
+#define MINUS_FIVE(z) absl::ToDoubleSeconds(z) - 5
+  x = MINUS_FIVE(d);
+#undef MINUS_FIVE
+}