feat(fuzz): Generate Match expressions and statements

[aakoshh]

Description

Problem*

Resolves #7926

Summary*

Implement match statements in the AST generator.

Additional Context

We are generating the what a match statement looks like in the monomorphized AST, but doing so without having in mind a full match statement in Noir, rather, just doing a single layer.

For example take this program:

global G: (u32, u32) = (2, 3);
fn main() -> pub u8 {
  match G {
    (2, _) => 1, 
    (_, 3) => 2, 
    (4, _) => 3, 
    _ => 4
  }
}

It turns into the following AST:

global G$g0: (u32, u32) = (2, 3);
fn main$f0() -> pub u8 {
    {
        let internal variable$l0 = G$g0;
        match $0 {
            ($1, $2) => match $1 {
                2 => {
                    let _$l3 = internal_match_variable_1$l2;
                    1
                },
                4 => match $2 {
                    3 => {
                        let _$l4 = internal_match_variable_0$l1;
                        2
                    },
                    _ => {
                        let _$l5 = internal_match_variable_1$l2;
                        3
                    },
                },
                _ => match $2 {
                    3 => {
                        let _$l6 = internal_match_variable_0$l1;
                        2
                    },
                    _ => {
                        let _$l7 = internal variable$l0;
                        4
                    },
                },
            },
        }
    }
}

So, it's a series of simpler match statements, on one variable at a time. The AST fuzzer generates only one random match, which can be:

• a bool variable against true, false, _
• a numeric variable against some random values and _ (wanted to do ranges but the frontend doesn't parse them)
• a tuple gets matched and individual fields introduced as local variables

I added support for variable names in the Match so that I can print a parseable AST.

The mono test which tests the AST roundtrip is currently not enabled. Example of the difference between how the generated AST is parsed back and printed are as follows:

Extra internal variables introduced by the compiler:

-                    match idx_b {
-                        3379574630 => if G_B {
-                            assert((idx_b <= (1329894387 - 3967336669)), "ETA")
-                            break
-                        } else {
-                            let e = (-((idx_b as Field) * (idx_b as Field)), (idx_b as Field))
-                        },
-                        3478020418 => (),
-                        _ => (),
+                    {
+                        let internal variable = idx_b
+                        match internal variable {
+                            3379574630 => if G_B {
+                                assert((idx_b <= (1329894387 - 3967336669)), "ETA")
+                                break
+                            } else {
+                                let e = (-((idx_b as Field) * (idx_b as Field)), (idx_b as Field))
+                            },
+                            3478020418 => (),
+                            _ => {
+                                let _ = internal variable
+                                ()
+                            },
+                        }

Never matched cases removed by the compiler:

-                match a {
-                    true => func_4((&mut "OF"), ctx_limit),
-                    true => func_4((&mut "FI"), ctx_limit),
-                    false => G_A,
-                    _ => func_4((&mut "SJ"), ctx_limit),
+                {
+                    let internal variable = a
+                    match internal variable {
+                        false => G_A,
+                        true => func_4((&mut "OF"), ctx_limit),
+                    }

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Test Suite Duration'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: ce217e7	Previous: 913ee63	Ratio
test_report_zkpassport_noir-ecdsa_	130 s	104 s	1.25
test_report_zkpassport_noir_rsa_	2 s	1 s	2

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[aakoshh]

Latest test failures need #9195

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 327d0ce	Previous: 11d86ef	Ratio
private-kernel-inner	0.021 s	0.016 s	1.31

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench