I'll just implement two-phase dce based on usage graph.

Author: kdy1

ecmascript/transforms/Cargo.toml

@@ -26,6 +26,7 @@ log = "0.4.8"
 num-bigint = {version = "0.2", features = ["serde"]}
 once_cell = "1"
 ordered-float = "1.0.1"
+petgraph = "0.5.1"
 phf = {version = "0.8.0", features = ["macros"]}
 regex = "1"
 retain_mut = "=0.1.1"

ecmascript/transforms/src/optimization/simplify/dce/analyzer.rs

@@ -0,0 +1,2 @@
+#[derive(Debug)]
+pub struct Scope {}

ecmascript/transforms/src/optimization/simplify/dce/mod.rs

@@ -22,6 +22,7 @@ macro_rules! preserve {
     };
 }
 
+mod analyzer;
 mod side_effect;
 
 #[derive(Debug)]