Homework 3

src/cd/frontend/semantic/SemanticFailure.java

@@ -0,0 +1,127 @@
+package cd.frontend.semantic;
+
+/** 
+ * Thrown by the semantic checker when a semantic error is detected
+ * in the user's program. */
+public class SemanticFailure extends RuntimeException {
+	private static final long serialVersionUID = 5375946759285719123L;
+	
+	public enum Cause {
+		/**
+		 * Caused by a nested method being found.  Those are not 
+		 * supported.
+		 */
+		NESTED_METHODS_UNSUPPORTED,
+		
+		/** 
+		 * Caused by an assignment to either a final field, {@code this},
+		 * or some other kind of expression which cannot be assigned to.
+		 * <b>Not</b> used for type errors in assignments, which fall
+		 * under {@link #TYPE_ERROR}. */
+		NOT_ASSIGNABLE,
+
+		/** The value of a final field is not a compile-time constant */
+		NOT_A_CONSTANT_EXPR,
+
+		/** Two variables, fields, methods, or classes with the same name 
+		 *  were declared in the same scope */
+		DOUBLE_DECLARATION,
+
+		/** A field was accessed that does not exist */
+		NO_SUCH_FIELD,
+		
+		/** A method was called that does not exist */
+		NO_SUCH_METHOD,
+		
+		/** 
+		 * A variable or other identifier was used in a method
+		 * body which has no corresponding declaration */
+		NO_SUCH_VARIABLE,
+		
+		/** 
+		 * A method with a return type is missing a return statement among one of its paths */
+		MISSING_RETURN,
+		
+		/** 
+		 * Can occur in many contents:
+		 * <ul>
+		 * <li> Assignment to a variable from an expression of wrong type
+		 * <li> A parameter in a method invocation had the wrong type
+		 * <li> A condition of a while loop or if statement was not boolean
+		 * <li> A non-array was indexed (i.e., a[i] where a is not an array)
+		 * <li> The index was not an int (i.e., a[i] where i is not an int)
+		 * <li> Arithmetic operators (+,-,etc) used with non-int type
+		 * <li> Boolean operators (!,&&,||,etc) used with non-boolean type
+		 * <li> Method or field accessed on non-object type
+		 * <li> {@code write()} is used with non-int argument
+		 * <li> An invalid cast was detected (i.e., a cast to a type that
+		 * is not a super- or sub-type of the original type).
+		 * <li> The size of an array in a new expression was not an
+		 * int (i.e., new A[i] where i is not an int)
+		 * </ul>
+		 */
+		TYPE_ERROR,
+		
+		/**
+		 * A class is its own super class
+		 */
+		CIRCULAR_INHERITANCE,
+		
+		/**
+		 * One of the following:
+		 * <ul>
+		 * <li>No class {@code Main}
+		 * <li>Class {@code Main} does not have a method {@code main()}
+		 * <li>The method {@code main} has > 0 parameters.
+		 * <li>The method {@code main} has a non-void return type.
+		 * </ul>
+		 */
+		INVALID_START_POINT,
+		
+		/**
+		 * A class {@code Object} was defined.  This class is implicitly
+		 * defined and cannot be defined explicitly.
+		 */
+		OBJECT_CLASS_DEFINED,
+		
+		/**
+		 * A type name was found for which no class declaration exists.
+		 * This can occur in many contexts:
+		 * <ul>
+		 * <li>The extends clause on a class declaration.
+		 * <li>A cast.
+		 * <li>A new expression.
+		 * </ul>
+		 */
+		NO_SUCH_TYPE,
+		
+		/**
+		 * The parameters of an overridden method have different types
+		 * from the base method, there is a different 
+		 * number of parameters, or the return value is different.
+		 */
+		INVALID_OVERRIDE,
+		
+		/** A method was called with the wrong number of arguments */
+		WRONG_NUMBER_OF_ARGUMENTS,
+		
+		/** 
+		 * Indicates the use of a local variable that may not have been
+		 * initialized (ACD only).
+		 */
+		POSSIBLY_UNINITIALIZED,
+	}
+	
+	public final Cause cause;
+	
+	public SemanticFailure(Cause cause) {
+		super(cause.name());
+		this.cause = cause;
+	}
+	
+	public SemanticFailure(Cause cause, String format, Object... args) {
+		super(String.format(format, args));
+		this.cause = cause;
+	}
+	
+}