Fix #14848 FP compareValueOutOfTypeRangeError and knownConditionTrueFalse with unsigned arithmetic (cppcheck-opensource#8658)

Co-authored-by: chrchr-github <noreply@github.com>

Author: chrchr-github

lib/vf_settokenvalue.cpp

@@ -613,7 +613,7 @@ namespace ValueFlow
         }
 
         // unary minus
-        else if (parent->isUnaryOp("-")) {
+        else if (parent->isUnaryOp("-") && !astIsUnsigned(parent)) {
             for (const Value &val : tok->values()) {
                 if (!val.isIntValue() && !val.isFloatValue())
                     continue;

test/testvalueflow.cpp

@@ -1269,6 +1269,12 @@ class TestValueFlow : public TestFixture {
         ASSERT_EQUALS(1U, values.size());
         ASSERT_EQUALS(-10, values.back().intvalue);
 
+        code = "bool f(unsigned a) {\n" // #14848
+               "    bool x = -a < 1;\n"
+               "    return x;\n"
+               "}";
+        ASSERT_EQUALS(false, testValueOfXKnown(code, 3U, 1));
+
         // Logical and
         code = "void f(bool b) {\n"
                "   bool x = false && b;\n"