Fix #12712 FN duplicateCondition with function in namespace (#6386)

Author: chrchr-github

lib/astutils.cpp

@@ -1684,8 +1684,6 @@ bool isSameExpression(bool macro, const Token *tok1, const Token *tok2, const Se
                     return false;
             } else {
                 const Token * ftok = tok1;
-                if (Token::simpleMatch(tok1->previous(), "::"))
-                    ftok = tok1->previous();
                 if (!settings.library.isFunctionConst(ftok) && !ftok->isAttributeConst() && !ftok->isAttributePure())
                     return false;
             }

test/testcondition.cpp

@@ -5558,6 +5558,12 @@ class TestCondition : public TestFixture {
               "}\n");
         ASSERT_EQUALS("[test.cpp:4] -> [test.cpp:6]: (style) The if condition is the same as the previous if condition\n", errout_str());
 
+        check("void f(double d) {\n" // #12712
+              "    if (std::isfinite(d)) {}\n"
+              "    if (std::isfinite(d)) {}\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2] -> [test.cpp:3]: (style) The if condition is the same as the previous if condition\n", errout_str());
+
         // do not crash
         check("void assign(const MMA& other) {\n"
               "    if (mPA.cols != other.mPA.cols || mPA.rows != other.mPA.rows)\n"