Demangle nx... syntax for noexcept(e) as an expression in a dependent signature.

PiperOrigin-RevId: 640590102
Change-Id: I2641cddd35119062328a197162bb700d8309fc05

absl/debugging/internal/demangle.cc

@@ -1998,6 +1998,7 @@ static bool ParseBracedExpression(State *state) {
 //              ::= st <type>
 //              ::= at <type>
 //              ::= az <expression>
+//              ::= nx <expression>
 //              ::= <template-param>
 //              ::= <function-param>
 //              ::= sZ <template-param>
@@ -2136,6 +2137,12 @@ static bool ParseExpression(State *state) {
   }
   state->parse_state = copy;
 
+  // noexcept(expression) appearing as an expression in a dependent signature
+  if (ParseTwoCharToken(state, "nx") && ParseExpression(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
   // sizeof...(pack)
   //
   // <expression> ::= sZ <template-param>

absl/debugging/internal/demangle_test.cc

@@ -1128,6 +1128,21 @@ TEST(Demangle, AlignofExpression) {
   EXPECT_STREQ("f<>()", tmp);
 }
 
+TEST(Demangle, NoexceptExpression) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> void f(T (&a)[noexcept(T{})]) {}
+  // template void f<int>(int (&)[noexcept(int{})]);
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // void f<int>(int (&) [noexcept (int{})])
+  EXPECT_TRUE(Demangle("_Z1fIiEvRAnxtlT_E_S0_", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 TEST(Demangle, ThreadLocalWrappers) {
   char tmp[80];