fix(es/transforms/optimization): Fix dead_branch_remover (#1827)

swc_ecma_transforms_optimization: - Preserve side effects of a while statement even if it's a infinite loop. (#1825)
swc-project · Jun 16, 2021 · b5a7a3f · b5a7a3f
1 parent 4c8d68b
commit b5a7a3f
Show file tree

Hide file tree

Showing 3 changed files with 33 additions and 8 deletions.
diff --git a/ecmascript/transforms/optimization/Cargo.toml b/ecmascript/transforms/optimization/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2018"
 license = "Apache-2.0/MIT"
 name = "swc_ecma_transforms_optimization"
 repository = "https://github.com/swc-project/swc.git"
-version = "0.22.0"
+version = "0.22.1"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]

diff --git a/ecmascript/transforms/optimization/src/simplify/branch/mod.rs b/ecmascript/transforms/optimization/src/simplify/branch/mod.rs
@@ -843,13 +843,17 @@ impl Fold for Remover {
             Stmt::While(s) => {
                 if let (purity, Known(v)) = s.test.as_bool() {
                     if v {
-                        Stmt::While(WhileStmt {
-                            test: Box::new(Expr::Lit(Lit::Bool(Bool {
-                                span: s.test.span(),
-                                value: true,
-                            }))),
-                            ..s
-                        })
+                        if purity.is_pure() {
+                            Stmt::While(WhileStmt {
+                                test: Box::new(Expr::Lit(Lit::Bool(Bool {
+                                    span: s.test.span(),
+                                    value: true,
+                                }))),
+                                ..s
+                            })
+                        } else {
+                            Stmt::While(s)
+                        }
                     } else {
                         let body = s.body.extract_var_ids_as_var();
                         let body = body.map(Decl::Var).map(Stmt::Decl);

diff --git a/ecmascript/transforms/optimization/src/simplify/branch/tests.rs b/ecmascript/transforms/optimization/src/simplify/branch/tests.rs
@@ -1766,3 +1766,24 @@ fn return_function_hoisting() {
         }",
     );
 }
+
+#[test]
+fn issue_1825() {
+    test(
+        "
+        function p(){
+            throw new Error('Something');
+        }
+        
+        while ((p(), 1)) {
+            console.log('Hello world');
+        }
+        ",
+        "
+        function p() {
+            throw new Error('Something');
+        }
+        while(p(), 1)console.log('Hello world');
+        ",
+    );
+}