try (EvaluationContext.ScopeContext context = openScope()) {
            beforeReadNoProducer(context, consumer);
            return doCalculateValue(context, consumer);
        }
    }

    @Override
    protected Value<? extends T> calculateOwnValue(ValueConsumer consumer) {
        try (EvaluationContext.ScopeContext context = openScope()) {
            beforeRead(context, consumer);

			}
		default:
			check.errorf(s, InvalidSyntaxTree, "branch statement: %s", s.Tok)
		}

	case *ast.BlockStmt:
		check.openScope(s, "block")
		defer check.closeScope()

		check.stmtList(inner, s.List)

	case *ast.IfStmt:
		check.openScope(s, "if")
		defer check.closeScope()

		check.simpleStmt(s.Init)
		var x operand
		check.expr(nil, &x, s.Cond)

			fallthrough
		default:
			check.errorf(s, InvalidSyntaxTree, "branch statement: %s", s.Tok)
		}

	case *syntax.BlockStmt:
		check.openScope(s, "block")
		defer check.closeScope()

		check.stmtList(inner, s.List)

	case *syntax.IfStmt:
		check.openScope(s, "if")
		defer check.closeScope()

		check.simpleStmt(s.Init)
		var x operand
		check.expr(nil, &x, s.Cond)

        //  Without the safety net of the EvaluationContext, it can cause hard-to-debug exceptions.
        try (EvaluationContext.ScopeContext context = openScope()) {
            return getSupplier(context);
        }
    }

    public DefaultProperty<T> provider(Provider<? extends T> provider) {
        set(provider);
        return this;
    }

// Implementation

// funcType type-checks a function or method type.
func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []*syntax.Field, ftyp *syntax.FuncType) {
	check.openScope(ftyp, "function")
	check.scope.isFunc = true
	check.recordScope(ftyp, check.scope)
	sig.scope = check.scope
	defer check.closeScope()

	if recvPar != nil {
		// collect generic receiver type parameters, if any

				if !versionErr && !buildcfg.Experiment.AliasTypeParams {
					check.error(tdecl, UnsupportedFeature, "generic type alias requires GOEXPERIMENT=aliastypeparams")
					versionErr = true
				}
				check.openScope(tdecl, "type parameters")
				defer check.closeScope()
				check.collectTypeParams(&alias.tparams, tdecl.TParamList)
			}

			rhs = check.definedType(tdecl.Type, obj)
			assert(rhs != nil)

				if !versionErr && !buildcfg.Experiment.AliasTypeParams {
					check.error(tdecl, UnsupportedFeature, "generic type alias requires GOEXPERIMENT=aliastypeparams")
					versionErr = true
				}
				check.openScope(tdecl, "type parameters")
				defer check.closeScope()
				check.collectTypeParams(&alias.tparams, tdecl.TypeParams)
			}

			rhs = check.definedType(tdecl.Type, obj)
			assert(rhs != nil)

        }

        @Override
        protected Value<? extends Set<K>> calculateOwnValue(ValueConsumer consumer) {
            try (EvaluationContext.ScopeContext context = DefaultMapProperty.this.openScope()) {
                beforeRead(context, consumer);
                return getSupplier(context).calculateKeys(consumer);
            }
        }
    }