/**
* Perform type propagation through a given expression, returning the type of value that is
* returned by evaluating this expression.
*
* @param e
* @param environment
* @param generics
* @param context
* @return
*/
private SemanticType propagate(
Expr e,
HashMap<String, SemanticType> environment,
HashSet<String> generics,
WyalFile.Context context) {
SemanticType t;
if (e instanceof Expr.Variable) {
t = propagate((Expr.Variable) e, environment, generics, context);
} else if (e instanceof Expr.Constant) {
t = propagate((Expr.Constant) e, environment, generics, context);
} else if (e instanceof Expr.Unary) {
t = propagate((Expr.Unary) e, environment, generics, context);
} else if (e instanceof Expr.Binary) {
t = propagate((Expr.Binary) e, environment, generics, context);
} else if (e instanceof Expr.Ternary) {
t = propagate((Expr.Ternary) e, environment, generics, context);
} else if (e instanceof Expr.Nary) {
t = propagate((Expr.Nary) e, environment, generics, context);
} else if (e instanceof Expr.Quantifier) {
t = propagate((Expr.Quantifier) e, environment, generics, context);
} else if (e instanceof Expr.FunCall) {
t = propagate((Expr.FunCall) e, environment, generics, context);
} else if (e instanceof Expr.IndexOf) {
t = propagate((Expr.IndexOf) e, environment, generics, context);
} else {
internalFailure("unknown expression encountered (" + e + ")", filename, e);
return null;
}
e.attributes().add(new TypeAttribute(t));
return returnType(e);
}
/**
* Calculate the most precise type that captures those possible values a given expression can
* evaluate to.
*
* @param e
* @return
*/
public static SemanticType returnType(Expr e) {
SemanticType type = e.attribute(TypeAttribute.class).type;
if (e instanceof Expr.Variable || e instanceof Expr.Constant || e instanceof Expr.Quantifier) {
return type;
} else if (e instanceof Expr.Unary) {
Expr.Unary ue = (Expr.Unary) e;
switch (ue.op) {
case NOT:
return SemanticType.Bool;
case NEG:
return type;
case LENGTHOF:
return SemanticType.Int;
}
} else if (e instanceof Expr.Binary) {
Expr.Binary ue = (Expr.Binary) e;
switch (ue.op) {
case ADD:
case SUB:
case MUL:
case DIV:
case REM:
case SETUNION:
case SETINTERSECTION:
case LISTAPPEND:
case RANGE:
return type;
case EQ:
case NEQ:
case IMPLIES:
case IFF:
case LT:
case LTEQ:
case GT:
case GTEQ:
case IN:
case SUBSET:
case SUBSETEQ:
case SUPSET:
case SUPSETEQ:
return SemanticType.Bool;
}
} else if (e instanceof Expr.Ternary) {
Expr.Ternary ue = (Expr.Ternary) e;
switch (ue.op) {
case UPDATE:
case SUBLIST:
return type;
}
} else if (e instanceof Expr.Nary) {
Expr.Nary ue = (Expr.Nary) e;
switch (ue.op) {
case AND:
case OR:
return SemanticType.Bool;
case TUPLE:
case SET:
case LIST:
return type;
}
} else if (e instanceof Expr.IndexOf) {
Expr.IndexOf ue = (Expr.IndexOf) e;
if (type instanceof SemanticType.EffectiveTuple) {
SemanticType.EffectiveTuple tt = (SemanticType.EffectiveTuple) type;
Value.Integer idx = (Value.Integer) ((Expr.Constant) ue.index).value;
return tt.tupleElement(idx.value.intValue());
} else {
SemanticType.Set st = (SemanticType.Set) type;
SemanticType.EffectiveTuple tt = (SemanticType.EffectiveTuple) st.element();
return tt.tupleElement(1);
}
} else {
Expr.FunCall fc = (Expr.FunCall) e;
return ((SemanticType.Function) type).to();
}
// should be deadcode.
throw new IllegalArgumentException("Invalid opcode for expression");
}