EssentialTypes: Fix integer constant types

Integer constants are only subject to the stlr or utlr if they are type
int, signed int or unsigned int, otherwise they have the standard type.

Fixes issues with RULE 12.2.

Author: lcartey

c/misra/src/codingstandards/c/misra/EssentialTypes.qll

@@ -355,13 +355,17 @@ class EssentialLiteral extends EssentialExpr, Literal {
     else (
       if this.(CharLiteral).getCharacter().length() = 1
       then result instanceof PlainCharType
-      else (
-        getStandardType().(IntegralType).isSigned() and
-        result = stlr(this)
-        or
-        not getStandardType().(IntegralType).isSigned() and
-        result = utlr(this)
-      )
+      else
+        exists(Type underlyingStandardType |
+          underlyingStandardType = getStandardType().getUnderlyingType()
+        |
+          if underlyingStandardType instanceof IntType
+          then
+            if underlyingStandardType.(IntType).isSigned()
+            then result = stlr(this)
+            else result = utlr(this)
+          else result = underlyingStandardType
+        )
     )
   }
 }

c/misra/test/c/misra/EssentialTypes.expected

@@ -38,3 +38,6 @@
 | test.c:26:3:26:3 | f | float | float | essentially Floating type |
 | test.c:27:3:27:5 | f32 | float32_t | float32_t | essentially Floating type |
 | test.c:28:3:28:6 | cf32 | float | float | essentially Floating type |
+| test.c:32:3:32:3 | 1 | signed char | signed char | essentially Signed type |
+| test.c:33:3:33:4 | 1 | unsigned char | unsigned char | essentially Unsigned type |
+| test.c:34:3:34:5 | 1 | unsigned long | unsigned long | essentially Unsigned type |

c/misra/test/c/misra/test.c

@@ -26,4 +26,10 @@ void testCategoriesForComplexTypes() {
   f;    // Should be essentially Floating type
   f32;  // Should be essentially Floating type
   cf32; // Should be essentially Floating type
+}
+
+void testConstants() {
+  1;   // Essentially signed char
+  1U;  // Essentially unsigned char
+  1UL; // Essentially unsigned long
 }