[Feature] String Reducers + Canonicalization

[gluax]

🚀 Feature

The goal is to add string to the Phases Reducer, allowing type-inference to handle characters.
Depends on #943.

Motivation

Right now, each of the AST and ASG relies on a reducer to handle certain phases such as canonicalization, type inference, etc.
The goal is to update the Reducers allowing for compilation.

Implementation

AST

• Reducer
  • A new function reduce_string should be added to the trait ReconstructingReducer block leo/ast/src/reducer/reconstructing_reducer.rs. It should return an Expression.
  • Need to modify reduce_value to return an Expression.
• Director
  • A new function reduce_string should be added to the impl<R: ReconstructingReducer> ReconstructingDirector<R> block leo/ast/src/reducer/reconstructing_director.rs. The function should return the string Value Expression Node wrapped in an Expression Node.
  • The reduce_value function should match the string Value Expression Node and call reduce_string. It should be modified to return an expression.
  • The reduce_expression function should return the expression rather than type wrapping it.
• Canonicalization
  • A new function reduce_string should be added to the impl ReconstructingReducer for Canonicalizer block.
  • The function should convert the string AST Node to an ArrayInline Expression Node.

Tests

• Compiler Tests:
  • Assigning a string.
    • Explicit.
    • Non-Explicit. Type Inference Should be tested here as well.
  • Should test after Canonicalization a string is an inline-array.
  • Passing a string to functions.
  • Circuit member variable string fields.
  • Global const string.

[damirka]

Closed by #957.