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Should we go ahead and do it?
Pros:

• Closer to Source 1 specs
• We learn how to extend type inference support to union types

Cons:

• Harder to implement
• Enforcing same types for every return statement helps to enforce correctness of programs

Write test cases for constant declarations

Write test cases for type inference for blocks

Example program:

true || false;
true && true;
true === true;

Trying this:
const x = true || false;
Does not infer x as boolean.

Reason being x is supposed to take on the type of the second argument.

• Have it conform to specs
• Have clearer error messages

Related to #33

Write test cases for conditional statements and conditional expressions

Write test cases for function declarations

• Monomorphic
• Polymorphic

Implement Type Inference for blocks:

• Separate type environment for each block (Scoping)
• Need to take note of functions as well.

The following test cases shouldn't work:

// Should throw error at x === 1
function someFunction2(x) {
    if (x === 1) {
        return x;
    } else {
        return x;
    }
}
someFunction2(true);

// TODO: Implement polymorphic types for functions
// Type variables in function declarations are polymorphic
// function identity(x) {
//     return x;
// }
// identity(3);
// identity("string") + "string";

Basic goal: monomorphic types
Advanced: type scheme representation

Initialise the type environment before program execution.

Deadline: this Sunday

Example program:

const x = 1;
x + 2;

Example programs:

1+1;
math_pi + 1;
1;

Write test cases for:

• Polymorphic functions
• Monomorphic functions
• VarArg functions

Infer literals, such as

• Numbers
• Strings
• Booleans
• Undefined