add std feature (#231)

- `std` feature is enabled by default
- By default enable #![no_std] compilation
- Import std create if `std` feature is enabled or if testing
- Use core, alloc types
- Make it clear where std types are being used
- In no std, use BTreeMap in place of HashMap.
   HashMap is not available in no std due to lack of a
   secure random number generator

Note: The project does not yet compile without std feature being specified.
But it's really close to being able to do so.

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

src/tests/interpreter/mod.rs

@@ -176,7 +176,7 @@ pub fn eval_file(
         let r = engine.eval_query(query.to_string(), enable_tracing)?;
         let r_full = engine_full.eval_query_and_all_rules(query.to_string(), enable_tracing)?;
         if r != r_full {
-            println!(
+            std::println!(
                 "{}\n{}",
                 serde_json::to_string_pretty(&r_full)?,
                 serde_json::to_string_pretty(&r)?
@@ -194,7 +194,7 @@ pub fn eval_file(
             let r = engine.eval_query(query.to_string(), enable_tracing)?;
             let r_full = engine_full.eval_query_and_all_rules(query.to_string(), enable_tracing)?;
             if r != r_full {
-                println!(
+                std::println!(
                     "{}\n{}",
                     serde_json::to_string_pretty(&r_full)?,
                     serde_json::to_string_pretty(&r)?
@@ -277,12 +277,12 @@ fn yaml_test_impl(file: &str) -> Result<()> {
     let yaml_str = std::fs::read_to_string(file)?;
     let test: YamlTest = serde_yaml::from_str(&yaml_str)?;
 
-    println!("running {file}");
+    std::println!("running {file}");
 
     for case in test.cases {
-        print!("case {} ", case.note);
+        std::print!("case {} ", case.note);
         if case.skip == Some(true) {
-            println!("skipped");
+            std::println!("skipped");
             continue;
         }
 
@@ -329,13 +329,13 @@ fn yaml_test_impl(file: &str) -> Result<()> {
                             expected
                         );
                     }
-                    println!("{actual}");
+                    std::println!("{actual}");
                 }
                 _ => return Err(actual),
             },
         }
 
-        println!("passed");
+        std::println!("passed");
     }
 
     Ok(())

src/tests/scheduler/analyzer/mod.rs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+use crate::*;
 use crate::{ast::*, lexer::*, parser::*, scheduler::*};
 use anyhow::{bail, Result};
 use serde::{Deserialize, Serialize};
@@ -73,25 +74,25 @@ fn analyze_file(regos: &[String], expected_scopes: &[Scope]) -> Result<()> {
             to_string_set(scope.inputs.iter()),
             expected_scopes[idx].inputs
         );
-        println!("scope {idx} matched.")
+        std::println!("scope {idx} matched.")
     }
 
     Ok(())
 }
 
 fn yaml_test_impl(file: &str) -> Result<()> {
-    println!("\nrunning {file}");
+    std::println!("\nrunning {file}");
 
     let yaml_str = std::fs::read_to_string(file)?;
     let test: YamlTest = serde_yaml::from_str(&yaml_str)?;
 
     for case in &test.cases {
-        print!("\ncase {} ", case.note);
+        std::print!("\ncase {} ", case.note);
         analyze_file(&case.modules, &case.scopes)?;
-        println!("passed");
+        std::println!("passed");
     }
 
-    println!("{} cases passed.", test.cases.len());
+    std::println!("{} cases passed.", test.cases.len());
     Ok(())
 }
 

src/tests/scheduler/mod.rs

@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 use crate::scheduler::*;
+use crate::*;
 use anyhow::{bail, Result};
 
 mod analyzer;
@@ -20,7 +21,7 @@ fn make_info(definitions: &[(&'static str, &[&'static str])]) -> StmtInfo<&'stat
 
 fn print_stmts(stmts: &[&str], order: &[u16]) {
     for idx in order.iter().cloned() {
-        println!("{}", stmts[idx as usize]);
+        std::println!("{}", stmts[idx as usize]);
     }
 }
 
@@ -29,7 +30,7 @@ fn check_result(stmts: &[&str], expected: &[&str], r: SortResult) -> Result<()>
         SortResult::Order(order) => {
             print_stmts(stmts, &order);
             for (i, o) in order.iter().cloned().enumerate() {
-                println!("{:30}{}", stmts[o as usize], expected[i]);
+                std::println!("{:30}{}", stmts[o as usize], expected[i]);
             }
             for (i, o) in order.iter().cloned().enumerate() {
                 assert_eq!(stmts[o as usize], expected[i]);