Demangle decltype(expr)::nested_type (NDT...E).

PiperOrigin-RevId: 638094845
Change-Id: I189ce357ccecbe6f341a311e405f9189bf6c0fee

absl/debugging/internal/demangle.cc

@@ -760,6 +760,7 @@ static bool ParseNestedName(State *state) {
 // <prefix> ::= <prefix> <unqualified-name>
 // <prefix> ::= <prefix> <unqualified-name>
 //          ::= <template-prefix> <template-args>
 //          ::= <template-prefix> <template-args>
 //          ::= <template-param>
 //          ::= <template-param>
+//          ::= <decltype>
 //          ::= <substitution>
 //          ::= <substitution>
 //          ::= # empty
 //          ::= # empty
 // <template-prefix> ::= <prefix> <(template) unqualified-name>
 // <template-prefix> ::= <prefix> <(template) unqualified-name>
@@ -771,7 +772,7 @@ static bool ParsePrefix(State *state) {
   bool has_something = false;
   bool has_something = false;
   while (true) {
   while (true) {
     MaybeAppendSeparator(state);
     MaybeAppendSeparator(state);
-    if (ParseTemplateParam(state) ||
+    if (ParseTemplateParam(state) || ParseDecltype(state) ||
         ParseSubstitution(state, /*accept_std=*/true) ||
         ParseSubstitution(state, /*accept_std=*/true) ||
         ParseUnscopedName(state) ||
         ParseUnscopedName(state) ||
         (ParseOneCharToken(state, 'M') && ParseUnnamedTypeName(state))) {
         (ParseOneCharToken(state, 'M') && ParseUnnamedTypeName(state))) {

absl/debugging/internal/demangle_test.cc

@@ -477,6 +477,22 @@ TEST(Demangle, DependentMemberOperatorCall) {
   EXPECT_STREQ("f<>()", tmp);
   EXPECT_STREQ("f<>()", tmp);
 }
 }
 
 
+TEST(Demangle, TypeNestedUnderDecltype) {
+  char tmp[80];
+
+  // Source:
+  //
+  // template <class T> struct S { using t = int; };
+  // template <class T> decltype(S<T>{})::t f() { return {}; }
+  // void g() { f<int>(); }
+  //
+  // Full LLVM demangling of the instantiation of f:
+  //
+  // decltype(S<int>{})::t f<int>()
+  EXPECT_TRUE(Demangle("_Z1fIiENDTtl1SIT_EEE1tEv", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 // Test subobject-address template parameters.
 // Test subobject-address template parameters.
 TEST(Demangle, SubobjectAddresses) {
 TEST(Demangle, SubobjectAddresses) {
   char tmp[80];
   char tmp[80];