Line an 8-inch-square baking pan with aluminum foil.

Combine sugar, evaporated milk, butter, and salt in a medium, heavy-duty saucepan over medium heat; bring to a full rolling boil, stirring constantly. Boil, stirring constantly, 4 to 5 minutes. Remove from heat.

Stir in marshmallows, chocolate morsels, pecans, and vanilla extract, stirring vigorously until marshmallows melted, about 1 minute. Pour into prepared baking pan; refrigerate until firm, about 2 hours. Lift from pan; remove foil. Cut into pieces.