Factor bespoke debug variables into debug_flags crate

compiler/debug_flags/src/lib.rs

@@ -0,0 +1,79 @@
+//! Flags for debugging the Roc compiler.
+//!
+//! Lists environment variable flags that can be enabled for verbose debugging features in debug
+//! builds of the compiler.
+//!
+//! For example, I might define the following alias to run cargo with all unifications and
+//! expanded type aliases printed:
+//!
+//! ```bash
+//! alias cargo="\
+//!            ROC_PRINT_UNIFICATIONS=1 \
+//!   ROC_PRETTY_PRINT_ALIAS_CONTENTS=1 \
+//!   cargo"
+//! ```
+//!
+//! More generally, I have the following:
+//!
+//! ```bash
+//! alias cargo="\
+//!     ROC_PRETTY_PRINT_ALIAS_CONTENTS=0 \
+//!              ROC_PRINT_UNIFICATIONS=0 \
+//!                ROC_PRINT_MISMATCHES=0 \
+//!   ROC_PRINT_IR_AFTER_SPECIALIZATION=0 \
+//!      ROC_PRINT_IR_AFTER_RESET_REUSE=0 \
+//!         ROC_PRINT_IR_AFTER_REFCOUNT=0 \
+//!         ROC_PRETTY_PRINT_IR_SYMBOLS=0 \
+//!   cargo"
+//! ```
+//!
+//! Now you can turn debug flags on and off as you like.
+
+#[macro_export]
+macro_rules! dbg_do {
+    ($flag:path, $expr:expr) => {
+        #[cfg(debug_assertions)]
+        {
+            if std::env::var($flag).unwrap_or("0".to_string()) != "0" {
+                $expr
+            }
+        }
+    };
+}
+
+macro_rules! flags {
+    ($($(#[doc = $doc:expr])+ $flag:ident)*) => {$(
+        $(#[doc = $doc])+
+        pub static $flag: &str = stringify!($flag);
+    )*};
+}
+
+flags! {
+    // ===Types===
+
+    /// Expands the contents of aliases during pretty-printing of types.
+    ROC_PRETTY_PRINT_ALIAS_CONTENTS
+
+    // ===Solve===
+
+    /// Prints type unifications, before and after they happen.
+    ROC_PRINT_UNIFICATIONS
+
+    /// Prints all type mismatches hit during type unification.
+    ROC_PRINT_MISMATCHES
+
+    // ===Mono===
+
+    /// Writes the mono IR to stderr after function specialization
+    ROC_PRINT_IR_AFTER_SPECIALIZATION
+
+    /// Writes the mono IR to stderr after insertion of reset/reuse instructions
+    ROC_PRINT_IR_AFTER_RESET_REUSE
+
+    /// Writes the mono IR to stderr after insertion of refcount instructions
+    ROC_PRINT_IR_AFTER_REFCOUNT
+
+    /// Instructs the mono IR pretty printer to dump pretty symbols and verbose
+    /// layout information
+    ROC_PRETTY_PRINT_IR_SYMBOLS
+}