feat: Add unquote function (#5497)

# Description

## Problem\*

Resolves #5478

## Summary\*

## Additional Context

## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [x] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: Michael J Klein <[email protected]>

compiler/noirc_frontend/src/parser/parser/types.rs

@@ -54,15 +54,7 @@ pub(super) fn parenthesized_type(
 }
 
 pub(super) fn maybe_comp_time() -> impl NoirParser<bool> {
-    keyword(Keyword::Comptime).or_not().validate(|opt, span, emit| {
-        if opt.is_some() {
-            emit(ParserError::with_reason(
-                ParserErrorReason::ExperimentalFeature("Comptime values"),
-                span,
-            ));
-        }
-        opt.is_some()
-    })
+    keyword(Keyword::Comptime).or_not().map(|opt| opt.is_some())
 }
 
 pub(super) fn field_type() -> impl NoirParser<UnresolvedType> {

noir_stdlib/src/meta/mod.nr

@@ -1 +1,8 @@
 mod type_def;
+
+/// Calling unquote as a macro (via `unquote!(arg)`) will unquote
+/// its argument. Since this is the effect `!` already does, `unquote`
+/// itself does not need to do anything besides return its argument.
+pub comptime fn unquote(code: Quoted) -> Quoted {
+    code
+}

test_programs/compile_success_empty/unquote/Nargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "unquote"
+type = "bin"
+authors = [""]
+compiler_version = ">=0.31.0"
+
+[dependencies]

test_programs/compile_success_empty/unquote/src/main.nr

@@ -0,0 +1,4 @@
+fn main() {
+    std::meta::unquote!(quote { assert(true); });
+    assert(std::meta::unquote!(quote { true }));
+}

tooling/nargo_cli/build.rs

@@ -61,7 +61,7 @@ const IGNORED_BRILLIG_TESTS: [&str; 11] = [
 /// Certain features are only available in the elaborator.
 /// We skip these tests for non-elaborator code since they are not
 /// expected to work there. This can be removed once the old code is removed.
-const IGNORED_NEW_FEATURE_TESTS: [&str; 9] = [
+const IGNORED_NEW_FEATURE_TESTS: [&str; 10] = [
     "macros",
     "wildcard_type",
     "type_definition_annotation",
@@ -71,6 +71,7 @@ const IGNORED_NEW_FEATURE_TESTS: [&str; 9] = [
     "comptime_slice_methods",
     "unary_operator_overloading",
     "unquote_multiple_items_from_annotation",
+    "unquote",
 ];
 
 fn read_test_cases(