fix Issue 22623 - ImportC: typedef'd struct definition tag not put in…

… symbol table

src/dmd/cparse.d

@@ -1691,6 +1691,26 @@ final class CParser(AST) : Parser!AST
                         isalias = false;
                     }
                 }
+                else if (auto tt = dt.isTypeTag())
+                {
+                    /* `struct tag;` and `struct tag { ... };`
+                     * always result in a declaration in the current scope
+                     */
+                    auto stag = (tt.tok == TOK.struct_) ? new AST.StructDeclaration(tt.loc, tt.id, false) :
+                                (tt.tok == TOK.union_)  ? new AST.UnionDeclaration(tt.loc, tt.id) :
+                                                          new AST.EnumDeclaration(tt.loc, tt.id, tt.base);
+                    stag.members = tt.members;
+                    if (!symbols)
+                        symbols = new AST.Dsymbols();
+                    symbols.push(stag);
+                    if (tt.tok == TOK.enum_)
+                    {
+                        if (!tt.members)
+                            error(tt.loc, "`enum %s` has no members", stag.toChars());
+                    }
+                    s = new AST.AliasDeclaration(token.loc, id, stag);
+                    isalias = false;
+                }
                 if (isalias)
                     s = new AST.AliasDeclaration(token.loc, id, dt);
             }

test/compilable/fix22623.c

@@ -0,0 +1,18 @@
+// https://issues.dlang.org/show_bug.cgi?id=22623
+
+struct S {
+    struct T *child;
+};
+
+typedef
+struct T {
+    int xyz;
+} U;
+
+void fn()
+{
+    struct S s;
+    struct T t;
+    if (s.child != &t)
+	;
+}