fix(es/minifier): Fix code for dropping unreachable statements (#6429)

**Related issue:** - Closes #6405.
swc-project · Nov 15, 2022 · bb544ba · bb544ba · github-actions · Nov 15, 2022
1 parent e117bc4
commit bb544ba
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Showing 3 changed files with 22 additions and 9 deletions.
diff --git a/crates/swc_ecma_minifier/src/compress/pure/dead_code.rs b/crates/swc_ecma_minifier/src/compress/pure/dead_code.rs
@@ -269,15 +269,7 @@ impl Pure<'_> {
                 );
             }
 
-            match stmts[idx].as_stmt() {
-                Some(Stmt::Return(ReturnStmt { arg: None, .. })) => {
-                    // Exclude return
-                    new_stmts.extend(stmts.drain(..idx));
-                }
-                _ => {
-                    new_stmts.extend(stmts.drain(..=idx));
-                }
-            }
+            new_stmts.extend(stmts.drain(..=idx));
 
             new_stmts.extend(hoisted_fns);
 

diff --git a/crates/swc_ecma_minifier/tests/pass-1/issue-6405/1/input.js b/crates/swc_ecma_minifier/tests/pass-1/issue-6405/1/input.js
@@ -0,0 +1,14 @@
+export const fn = () => {
+    let val;
+
+    if (!val) {
+        return undefined;
+        // works as expected if comment out below line
+        throw new Error('first');
+    }
+
+    if (val.a?.b !== true) { // Uncaught TypeError: Cannot read properties of undefined (reading 'a')
+        throw new Error('second');
+    }
+    return val;
+}
diff --git a/crates/swc_ecma_minifier/tests/pass-1/issue-6405/1/output.js b/crates/swc_ecma_minifier/tests/pass-1/issue-6405/1/output.js
@@ -0,0 +1,7 @@
+export const fn = ()=>{
+    let val;
+    if (!!val) {
+        if (val.a?.b !== !0) throw Error('second');
+        return val;
+    }
+};
Benchmark suite	Current: `bb544ba`	Previous: `9600308`	Ratio
`es/full/bugs-1`	`367751` ns/iter (`± 203364`)	`358728` ns/iter (`± 20211`)	`1.03`
`es/full/minify/libraries/antd`	`12738437892` ns/iter (`± 2721999605`)	`1970753614` ns/iter (`± 83209994`)	`6.46`
`es/full/minify/libraries/d3`	`2243799199` ns/iter (`± 495758453`)	`436403414` ns/iter (`± 15106176`)	`5.14`
`es/full/minify/libraries/echarts`	`9137695707` ns/iter (`± 627387443`)	`1649793064` ns/iter (`± 61295639`)	`5.54`
`es/full/minify/libraries/jquery`	`688761246` ns/iter (`± 144412401`)	`120893988` ns/iter (`± 7793123`)	`5.70`
`es/full/minify/libraries/lodash`	`696059032` ns/iter (`± 225730691`)	`139829224` ns/iter (`± 7717097`)	`4.98`
`es/full/minify/libraries/moment`	`280589590` ns/iter (`± 130493563`)	`67507421` ns/iter (`± 2083928`)	`4.16`
`es/full/minify/libraries/react`	`54290508` ns/iter (`± 10038943`)	`22202854` ns/iter (`± 1072765`)	`2.45`
`es/full/minify/libraries/terser`	`2407548044` ns/iter (`± 238808274`)	`359007216` ns/iter (`± 8807000`)	`6.71`
`es/full/minify/libraries/three`	`4214102218` ns/iter (`± 348135165`)	`616147879` ns/iter (`± 12528583`)	`6.84`
`es/full/minify/libraries/typescript`	`23813881571` ns/iter (`± 543816685`)	`3581732217` ns/iter (`± 45334056`)	`6.65`
`es/full/minify/libraries/victory`	`5954681550` ns/iter (`± 438502100`)	`881184048` ns/iter (`± 19875891`)	`6.76`
`es/full/minify/libraries/vue`	`1017633454` ns/iter (`± 213860154`)	`179471415` ns/iter (`± 4730819`)	`5.67`
`es/full/codegen/es3`	`35635` ns/iter (`± 4891`)	`34424` ns/iter (`± 3250`)	`1.04`
`es/full/codegen/es5`	`35582` ns/iter (`± 5846`)	`33917` ns/iter (`± 3412`)	`1.05`
`es/full/codegen/es2015`	`36014` ns/iter (`± 9531`)	`34112` ns/iter (`± 1702`)	`1.06`
`es/full/codegen/es2016`	`35165` ns/iter (`± 2406`)	`34087` ns/iter (`± 5975`)	`1.03`
`es/full/codegen/es2017`	`35357` ns/iter (`± 4231`)	`33948` ns/iter (`± 4008`)	`1.04`
`es/full/codegen/es2018`	`35639` ns/iter (`± 3679`)	`34556` ns/iter (`± 3726`)	`1.03`
`es/full/codegen/es2019`	`35685` ns/iter (`± 5038`)	`35521` ns/iter (`± 4079`)	`1.00`
`es/full/codegen/es2020`	`35407` ns/iter (`± 5120`)	`34688` ns/iter (`± 3803`)	`1.02`
`es/full/all/es3`	`327846481` ns/iter (`± 187578606`)	`212352806` ns/iter (`± 12823051`)	`1.54`
`es/full/all/es5`	`225360514` ns/iter (`± 183396960`)	`198628693` ns/iter (`± 10760155`)	`1.13`
`es/full/all/es2015`	`192773879` ns/iter (`± 162767019`)	`145676177` ns/iter (`± 5143401`)	`1.32`
`es/full/all/es2016`	`239316360` ns/iter (`± 122950047`)	`149710787` ns/iter (`± 13111995`)	`1.60`
`es/full/all/es2017`	`276547865` ns/iter (`± 160674054`)	`150991913` ns/iter (`± 6325256`)	`1.83`
`es/full/all/es2018`	`248456241` ns/iter (`± 168108418`)	`156666514` ns/iter (`± 14027559`)	`1.59`
`es/full/all/es2019`	`176506771` ns/iter (`± 114913441`)	`151802647` ns/iter (`± 9561704`)	`1.16`
`es/full/all/es2020`	`187976892` ns/iter (`± 65886548`)	`145116045` ns/iter (`± 8847937`)	`1.30`
`es/full/parser`	`1034504` ns/iter (`± 330922`)	`729070` ns/iter (`± 64347`)	`1.42`
`es/full/base/fixer`	`27362` ns/iter (`± 3639`)	`27598` ns/iter (`± 2217`)	`0.99`
`es/full/base/resolver_and_hygiene`	`95006` ns/iter (`± 10461`)	`91640` ns/iter (`± 7732`)	`1.04`
`serialization of ast node`	`232` ns/iter (`± 19`)	`223` ns/iter (`± 24`)	`1.04`
`serialization of serde`	`230` ns/iter (`± 17`)	`228` ns/iter (`± 24`)	`1.01`