feat: Reject with keyword usage

RVM does not plan to support the `with` keyword which is mainly used
for testing.

- introduce CompilerError::WithKeywordUnsupported and fail query compilation
  when any literal carries with_mods
- skip OPA test cases that hit the error

The "withkeyword" folder is retained in the TODO list to indicate its
lack of support.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/languages/rego/compiler/error.rs

@@ -15,6 +15,9 @@ pub enum CompilerError {
     #[error("Unknown builtin function: {name}")]
     UnknownBuiltinFunction { name: String },
 
+    #[error("the `with` keyword is not supported by the compiler yet")]
+    WithKeywordUnsupported,
+
     #[error("internal: missing context for yield")]
     MissingYieldContext,
 

src/languages/rego/compiler/mod.rs

@@ -10,7 +10,7 @@ mod queries;
 mod references;
 mod rules;
 
-pub use error::{CompilerError, Result};
+pub use error::{CompilerError, Result, SpannedCompilerError};
 
 use crate::ast::ExprRef;
 use crate::lexer::Span;

src/languages/rego/compiler/queries.rs

@@ -38,6 +38,9 @@ impl<'a> Compiler<'a> {
         stmts: &[&LiteralStmt],
     ) -> Result<()> {
         for (idx, stmt) in stmts.iter().enumerate() {
+            if !stmt.with_mods.is_empty() {
+                return Err(CompilerError::WithKeywordUnsupported.at(&stmt.span));
+            }
             let loop_exprs = self.get_statement_loops(stmt)?;
 
             if !loop_exprs.is_empty() {