Add generic function to fetch scope variables with a generic type (#293)

* Add generic way to fetch scope variables

* Use more specific error

---------

Co-authored-by: Pedro Fontana <[email protected]>

pkg/types/exec_scope_test.go

@@ -258,3 +258,21 @@ func TestErrExitMainScope(t *testing.T) {
 		t.Errorf("TestErrExitMainScope should fail with error: %s and fails with: %s", types.ErrCannotExitMainScop, err)
 	}
 }
+
+func TestFetchScopeVar(t *testing.T) {
+	scope := make(map[string]interface{})
+	scope["k"] = lambdaworks.FeltOne()
+
+	scopes := types.NewExecutionScopes()
+	scopes.EnterScope(scope)
+
+	result, err := types.FetchScopeVar[lambdaworks.Felt]("k", scopes)
+	if err != nil {
+		t.Errorf("TestGetLocalVariables failed with error: %s", err)
+
+	}
+	expected := lambdaworks.FeltOne()
+	if expected != result {
+		t.Errorf("TestGetLocalVariables failed, expected: %s, got: %s", expected.ToSignedFeltString(), result.ToSignedFeltString())
+	}
+}

pkg/types/exec_scopes.go

@@ -18,6 +18,10 @@ func ErrVariableNotInScope(varName string) error {
 	return ExecutionScopesError(errors.Errorf("Variable %s not in scope", varName))
 }
 
+func ErrVariableHasWrongType(varName string) error {
+	return ExecutionScopesError(errors.Errorf("Scope variable %s has wrong type", varName))
+}
+
 func NewExecutionScopes() *ExecutionScopes {
 	data := make([]map[string]interface{}, 1)
 	data[0] = make(map[string]interface{})
@@ -82,3 +86,20 @@ func (es *ExecutionScopes) Get(varName string) (interface{}, error) {
 	}
 	return val, nil
 }
+
+// Generic version of ExecutionScopes.Get which also handles casting
+func FetchScopeVar[T interface{}](varName string, scopes *ExecutionScopes) (T, error) {
+	locals, err := scopes.GetLocalVariables()
+	if err != nil {
+		return *new(T), err
+	}
+	valAny, prs := locals[varName]
+	if !prs {
+		return *new(T), ErrVariableNotInScope(varName)
+	}
+	val, ok := valAny.(T)
+	if !ok {
+		return *new(T), ErrVariableHasWrongType(varName)
+	}
+	return val, nil
+}