feat(es/minifier): Support more statements in seqential inliner (#6248)

**Description:** We now inline into the discriminant of a switch statement and into the initializer of for/for-in/for-of statements.
swc-project · Oct 26, 2022 · 86e265a · 86e265a · github-actions · Oct 26, 2022
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diff --git a/crates/swc/tests/tsc-references/for-of24.2.minified.js b/crates/swc/tests/tsc-references/for-of24.2.minified.js
@@ -1,3 +1,2 @@
 //// [for-of24.ts]
-var x;
-for (var v of x);
+for (var v of void 0);
diff --git a/crates/swc/tests/tsc-references/for-of29.2.minified.js b/crates/swc/tests/tsc-references/for-of29.2.minified.js
@@ -1,3 +1,2 @@
 //// [for-of29.ts]
-var iterableWithOptionalIterator;
-for (var v of iterableWithOptionalIterator);
+for (var v of void 0);
diff --git a/crates/swc/tests/tsc-references/for-of37.2.minified.js b/crates/swc/tests/tsc-references/for-of37.2.minified.js
@@ -1,8 +1,7 @@
 //// [for-of37.ts]
-var map = new Map([
+for (var v of new Map([
     [
         "",
         !0
     ]
-]);
-for (var v of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of38.2.minified.js b/crates/swc/tests/tsc-references/for-of38.2.minified.js
@@ -1,8 +1,7 @@
 //// [for-of38.ts]
-var map = new Map([
+for (var [k, v] of new Map([
     [
         "",
         !0
     ]
-]);
-for (var [k, v] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of39.2.minified.js b/crates/swc/tests/tsc-references/for-of39.2.minified.js
@@ -1,5 +1,5 @@
 //// [for-of39.ts]
-var map = new Map([
+for (var [k, v] of new Map([
     [
         "",
         !0
@@ -8,5 +8,4 @@ var map = new Map([
         "",
         0
     ]
-]);
-for (var [k, v] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of40.2.minified.js b/crates/swc/tests/tsc-references/for-of40.2.minified.js
@@ -1,8 +1,7 @@
 //// [for-of40.ts]
-var map = new Map([
+for (var [k = "", v = !1] of new Map([
     [
         "",
         !0
     ]
-]);
-for (var [k = "", v = !1] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of44.2.minified.js b/crates/swc/tests/tsc-references/for-of44.2.minified.js
@@ -1,5 +1,5 @@
 //// [for-of44.ts]
-var array = [
+for (var [num, strBoolSym] of [
     [
         0,
         ""
@@ -12,5 +12,4 @@ var array = [
         1,
         Symbol()
     ]
-];
-for (var [num, strBoolSym] of array);
+]);
diff --git a/crates/swc/tests/tsc-references/for-of45.2.minified.js b/crates/swc/tests/tsc-references/for-of45.2.minified.js
@@ -1,8 +1,8 @@
 //// [for-of45.ts]
-var k, v, map = new Map([
+var k, v;
+for ([k = "", v = !1] of new Map([
     [
         "",
         !0
     ]
-]);
-for ([k = "", v = !1] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of46.2.minified.js b/crates/swc/tests/tsc-references/for-of46.2.minified.js
@@ -1,8 +1,8 @@
 //// [for-of46.ts]
-var k, v, map = new Map([
+var k, v;
+for ([k = !1, v = ""] of new Map([
     [
         "",
         !0
     ]
-]);
-for ([k = !1, v = ""] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of49.2.minified.js b/crates/swc/tests/tsc-references/for-of49.2.minified.js
@@ -1,8 +1,8 @@
 //// [for-of49.ts]
-var k, v, map = new Map([
+var k, v;
+for ([k, ...[v]] of new Map([
     [
         "",
         !0
     ]
-]);
-for ([k, ...[v]] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of50.2.minified.js b/crates/swc/tests/tsc-references/for-of50.2.minified.js
@@ -1,8 +1,7 @@
 //// [for-of50.ts]
-var map = new Map([
+for (const [k, v] of new Map([
     [
         "",
         !0
     ]
-]);
-for (const [k, v] of map);
+]));
diff --git a/crates/swc/tests/tsc-references/for-of57.2.minified.js b/crates/swc/tests/tsc-references/for-of57.2.minified.js
@@ -1,3 +1,2 @@
 //// [for-of57.ts]
-var iter;
-for (let num of iter);
+for (let num of void 0);
diff --git a/crates/swc/tests/tsc-references/parserRealSource1.2.minified.js b/crates/swc/tests/tsc-references/parserRealSource1.2.minified.js
@@ -7,8 +7,7 @@ import _class_call_check from "@swc/helpers/src/_class_call_check.mjs";
         return logger.log(funcDescription + " completed in " + (end - start) + " msec"), result;
     }, stringToLiteral = function(value, length) {
         var result = "", addChar = function(index) {
-            var ch = value.charCodeAt(index);
-            switch(ch){
+            switch(value.charCodeAt(index)){
                 case 0x09:
                     result += "\\t";
                     break;

diff --git a/crates/swc/tests/tsc-references/stringLiteralsWithSwitchStatements03.2.minified.js b/crates/swc/tests/tsc-references/stringLiteralsWithSwitchStatements03.2.minified.js
@@ -1,12 +1,6 @@
 //// [stringLiteralsWithSwitchStatements03.ts]
-var x, z;
-switch(x){
+var z;
+switch(void 0){
     case randBool() ? "foo" : "baz":
-    case randBool(), "bar":
-    case "bar":
-    case "baz":
-    case "foo":
-    case "bar":
     case z || "baz":
-    case "baz":
 }
diff --git a/crates/swc_ecma_minifier/src/compress/optimize/sequences.rs b/crates/swc_ecma_minifier/src/compress/optimize/sequences.rs
@@ -581,9 +581,31 @@ where
             Stmt::Return(ReturnStmt { arg: Some(arg), .. }) => {
                 vec![Mergable::Expr(arg)]
             }
+
             Stmt::If(s) if options.sequences() => {
                 vec![Mergable::Expr(&mut s.test)]
             }
+
+            Stmt::Switch(s) if options.sequences() => {
+                vec![Mergable::Expr(&mut s.discriminant)]
+            }
+
+            Stmt::For(s) if options.sequences() => {
+                if let Some(VarDeclOrExpr::Expr(e)) = &mut s.init {
+                    vec![Mergable::Expr(e)]
+                } else {
+                    return None;
+                }
+            }
+
+            Stmt::ForOf(s) if options.sequences() => {
+                vec![Mergable::Expr(&mut s.right)]
+            }
+
+            Stmt::ForIn(s) if options.sequences() => {
+                vec![Mergable::Expr(&mut s.right)]
+            }
+
             Stmt::Throw(s) if options.sequences() => {
                 vec![Mergable::Expr(&mut s.arg)]
             }
@@ -624,7 +646,15 @@ where
         for stmt in stmts.iter_mut() {
             let is_end = matches!(
                 stmt.as_stmt(),
-                Some(Stmt::If(..) | Stmt::Throw(..) | Stmt::Return(..))
+                Some(
+                    Stmt::If(..)
+                        | Stmt::Throw(..)
+                        | Stmt::Return(..)
+                        | Stmt::Switch(..)
+                        | Stmt::For(..)
+                        | Stmt::ForIn(..)
+                        | Stmt::ForOf(..)
+                ) | None
             );
             let can_skip = match stmt.as_stmt() {
                 Some(Stmt::Decl(Decl::Fn(..))) => true,

diff --git a/crates/swc_ecma_minifier/tests/benches-full/echarts.js b/crates/swc_ecma_minifier/tests/benches-full/echarts.js
@@ -2428,8 +2428,7 @@
                 var frameIdx, isAdditive = null != this._additiveTrack, valueKey = isAdditive ? 'additiveValue' : 'value', keyframes = this.keyframes, kfsNum = this.keyframes.length, propName = this.propName, arrDim = this.arrDim, isValueColor = this.isValueColor;
                 if (percent < 0) frameIdx = 0;
                 else if (percent < this._lastFramePercent) {
-                    var start = Math.min(this._lastFrame + 1, kfsNum - 1);
-                    for(frameIdx = start; frameIdx >= 0 && !(keyframes[frameIdx].percent <= percent); frameIdx--);
+                    for(frameIdx = Math.min(this._lastFrame + 1, kfsNum - 1); frameIdx >= 0 && !(keyframes[frameIdx].percent <= percent); frameIdx--);
                     frameIdx = Math.min(frameIdx, kfsNum - 2);
                 } else {
                     for(frameIdx = this._lastFrame; frameIdx < kfsNum && !(keyframes[frameIdx].percent > percent); frameIdx++);
@@ -28477,8 +28476,7 @@
             if (offsets) {
                 var lastFrame = this._lastFrame;
                 if (t < this._lastFramePercent) {
-                    var start = Math.min(lastFrame + 1, len - 1);
-                    for(frame = start; frame >= 0 && !(offsets[frame] <= t); frame--);
+                    for(frame = Math.min(lastFrame + 1, len - 1); frame >= 0 && !(offsets[frame] <= t); frame--);
                     frame = Math.min(frame, len - 2);
                 } else {
                     for(frame = lastFrame; frame < len && !(offsets[frame] > t); frame++);

diff --git a/crates/swc_ecma_minifier/tests/benches-full/terser.js b/crates/swc_ecma_minifier/tests/benches-full/terser.js
@@ -417,8 +417,7 @@
                         return ret;
                     }(function(ch, i) {
                         if (is_big_int) return !1;
-                        var code = ch.charCodeAt(0);
-                        switch(code){
+                        switch(ch.charCodeAt(0)){
                             case 95:
                                 return numeric_separator = !0;
                             case 98:

diff --git a/crates/swc_ecma_minifier/tests/benches-full/three.js b/crates/swc_ecma_minifier/tests/benches-full/three.js
@@ -12078,21 +12078,18 @@
                                 return;
                             }
                             var path = new ShapePath();
-                            if (glyph.o) for(var outline = glyph._cachedOutline || (glyph._cachedOutline = glyph.o.split(' ')), i = 0, l = outline.length; i < l;){
-                                var action = outline[i++];
-                                switch(action){
-                                    case 'm':
-                                        x = outline[i++] * scale + offsetX, y = outline[i++] * scale + offsetY, path.moveTo(x, y);
-                                        break;
-                                    case 'l':
-                                        x = outline[i++] * scale + offsetX, y = outline[i++] * scale + offsetY, path.lineTo(x, y);
-                                        break;
-                                    case 'q':
-                                        cpx = outline[i++] * scale + offsetX, cpy = outline[i++] * scale + offsetY, cpx1 = outline[i++] * scale + offsetX, cpy1 = outline[i++] * scale + offsetY, path.quadraticCurveTo(cpx1, cpy1, cpx, cpy);
-                                        break;
-                                    case 'b':
-                                        cpx = outline[i++] * scale + offsetX, cpy = outline[i++] * scale + offsetY, cpx1 = outline[i++] * scale + offsetX, cpy1 = outline[i++] * scale + offsetY, cpx2 = outline[i++] * scale + offsetX, cpy2 = outline[i++] * scale + offsetY, path.bezierCurveTo(cpx1, cpy1, cpx2, cpy2, cpx, cpy);
-                                }
+                            if (glyph.o) for(var outline = glyph._cachedOutline || (glyph._cachedOutline = glyph.o.split(' ')), i = 0, l = outline.length; i < l;)switch(outline[i++]){
+                                case 'm':
+                                    x = outline[i++] * scale + offsetX, y = outline[i++] * scale + offsetY, path.moveTo(x, y);
+                                    break;
+                                case 'l':
+                                    x = outline[i++] * scale + offsetX, y = outline[i++] * scale + offsetY, path.lineTo(x, y);
+                                    break;
+                                case 'q':
+                                    cpx = outline[i++] * scale + offsetX, cpy = outline[i++] * scale + offsetY, cpx1 = outline[i++] * scale + offsetX, cpy1 = outline[i++] * scale + offsetY, path.quadraticCurveTo(cpx1, cpy1, cpx, cpy);
+                                    break;
+                                case 'b':
+                                    cpx = outline[i++] * scale + offsetX, cpy = outline[i++] * scale + offsetY, cpx1 = outline[i++] * scale + offsetX, cpy1 = outline[i++] * scale + offsetY, cpx2 = outline[i++] * scale + offsetX, cpy2 = outline[i++] * scale + offsetY, path.bezierCurveTo(cpx1, cpy1, cpx2, cpy2, cpx, cpy);
                             }
                             return {
                                 offsetX: glyph.ha * scale,

diff --git a/..._ecma_minifier/tests/fixture/next/33265/static/chunks/d6e1aeb5-38a8d7ae57119c23/output.js b/..._ecma_minifier/tests/fixture/next/33265/static/chunks/d6e1aeb5-38a8d7ae57119c23/output.js
@@ -10558,8 +10558,7 @@
                         return programMapTable;
                     }
                 }, parsePesType = function(packet, programMapTable) {
-                    var type = programMapTable[parsePid(packet)];
-                    switch(type){
+                    switch(programMapTable[parsePid(packet)]){
                         case streamTypes.H264_STREAM_TYPE:
                             return "video";
                         case streamTypes.ADTS_STREAM_TYPE:
@@ -10715,8 +10714,7 @@
                     }
                 }, inspectAac_ = function(bytes) {
                     for(var packet, endLoop = !1, audioCount = 0, sampleRate = null, timestamp = null, frameSize = 0, byteIndex = 0; bytes.length - byteIndex >= 3;){
-                        var type = probe.aac.parseType(bytes, byteIndex);
-                        switch(type){
+                        switch(probe.aac.parseType(bytes, byteIndex)){
                             case "timed-metadata":
                                 if (bytes.length - byteIndex < 10 || (frameSize = probe.aac.parseId3TagSize(bytes, byteIndex)) > bytes.length) {
                                     endLoop = !0;
@@ -10757,15 +10755,12 @@
                         pid: null,
                         table: null
                     }, result = {};
-                    for(var pid in parsePsi_(bytes, pmt), pmt.table)if (pmt.table.hasOwnProperty(pid)) {
-                        var type = pmt.table[pid];
-                        switch(type){
-                            case streamTypes.H264_STREAM_TYPE:
-                                result.video = [], parseVideoPes_(bytes, pmt, result), 0 === result.video.length && delete result.video;
-                                break;
-                            case streamTypes.ADTS_STREAM_TYPE:
-                                result.audio = [], parseAudioPes_(bytes, pmt, result), 0 === result.audio.length && delete result.audio;
-                        }
+                    for(var pid in parsePsi_(bytes, pmt), pmt.table)if (pmt.table.hasOwnProperty(pid)) switch(pmt.table[pid]){
+                        case streamTypes.H264_STREAM_TYPE:
+                            result.video = [], parseVideoPes_(bytes, pmt, result), 0 === result.video.length && delete result.video;
+                            break;
+                        case streamTypes.ADTS_STREAM_TYPE:
+                            result.audio = [], parseAudioPes_(bytes, pmt, result), 0 === result.audio.length && delete result.audio;
                     }
                     return result;
                 }, tsInspector = {

diff --git a/crates/swc_ecma_minifier/tests/fixture/next/react-pdf-renderer/output.js b/crates/swc_ecma_minifier/tests/fixture/next/react-pdf-renderer/output.js
@@ -8241,8 +8241,8 @@
                 return t.length < 2 ? "0" + t : t;
             }
             l.get = function(e) {
-                var t, r, n = e.substring(0, 3).toLowerCase();
-                switch(n){
+                var t, r;
+                switch(e.substring(0, 3).toLowerCase()){
                     case "hsl":
                         t = l.get.hsl(e), r = "hsl";
                         break;
@@ -9406,10 +9406,10 @@
                         stickToLeft: 3,
                         stickToRight: 4
                     }; t = e.charAt(r++);){
-                        var o = "." === t, a = !o && /\d/.test(t), u = o ? r - 1 == 0 ? i.stickToLeft : i.stickToRight : a ? i.level : i.alphabet;
-                        switch(u){
+                        var o = "." === t, a = !o && /\d/.test(t);
+                        switch(o ? r - 1 == 0 ? i.stickToLeft : i.stickToRight : a ? i.level : i.alphabet){
                             case i.alphabet:
-                                l || n.levels.push(0), n.text += t;
+                                u || n.levels.push(0), n.text += t;
                                 break;
                             case i.level:
                                 n.levels.push(parseInt(t));
@@ -9420,7 +9420,7 @@
                             case i.stickToRight:
                                 n.stickToRight = !0;
                         }
-                        var l = a;
+                        var u = a;
                     }
                     return n;
                 }
Benchmark suite	Current: `86e265a`	Previous: `01edb4f`	Ratio
`es/full/bugs-1`	`387271` ns/iter (`± 44005`)	`413795` ns/iter (`± 20077`)	`0.94`
`es/full/minify/libraries/antd`	`1919425798` ns/iter (`± 69578682`)	`2013578744` ns/iter (`± 45413342`)	`0.95`
`es/full/minify/libraries/d3`	`439895874` ns/iter (`± 9446188`)	`390547845` ns/iter (`± 31387493`)	`1.13`
`es/full/minify/libraries/echarts`	`1623574929` ns/iter (`± 86070476`)	`1704129352` ns/iter (`± 31177238`)	`0.95`
`es/full/minify/libraries/jquery`	`116698378` ns/iter (`± 2073008`)	`114639845` ns/iter (`± 2082991`)	`1.02`
`es/full/minify/libraries/lodash`	`130046915` ns/iter (`± 7912521`)	`141321460` ns/iter (`± 3149692`)	`0.92`
`es/full/minify/libraries/moment`	`67110690` ns/iter (`± 3357764`)	`124155576` ns/iter (`± 29574186`)	`0.54`
`es/full/minify/libraries/react`	`22592359` ns/iter (`± 1594457`)	`25326873` ns/iter (`± 2992753`)	`0.89`
`es/full/minify/libraries/terser`	`342963771` ns/iter (`± 18168980`)	`312746776` ns/iter (`± 9812501`)	`1.10`
`es/full/minify/libraries/three`	`544570838` ns/iter (`± 18009687`)	`532482669` ns/iter (`± 26915749`)	`1.02`
`es/full/minify/libraries/typescript`	`3392895098` ns/iter (`± 61855995`)	`3790116593` ns/iter (`± 81660888`)	`0.90`
`es/full/minify/libraries/victory`	`836893368` ns/iter (`± 32989528`)	`782618271` ns/iter (`± 59720608`)	`1.07`
`es/full/minify/libraries/vue`	`159378942` ns/iter (`± 6815178`)	`172810089` ns/iter (`± 3431816`)	`0.92`
`es/full/codegen/es3`	`34252` ns/iter (`± 1631`)	`39429` ns/iter (`± 2789`)	`0.87`
`es/full/codegen/es5`	`34251` ns/iter (`± 2242`)	`40071` ns/iter (`± 2865`)	`0.85`
`es/full/codegen/es2015`	`33984` ns/iter (`± 855`)	`38257` ns/iter (`± 2807`)	`0.89`
`es/full/codegen/es2016`	`33691` ns/iter (`± 1486`)	`39066` ns/iter (`± 1348`)	`0.86`
`es/full/codegen/es2017`	`33807` ns/iter (`± 2128`)	`38540` ns/iter (`± 1958`)	`0.88`
`es/full/codegen/es2018`	`33949` ns/iter (`± 1012`)	`38611` ns/iter (`± 1797`)	`0.88`
`es/full/codegen/es2019`	`34066` ns/iter (`± 701`)	`39887` ns/iter (`± 2290`)	`0.85`
`es/full/codegen/es2020`	`34042` ns/iter (`± 502`)	`38580` ns/iter (`± 1494`)	`0.88`
`es/full/all/es3`	`201231846` ns/iter (`± 10537410`)	`222064422` ns/iter (`± 5598935`)	`0.91`
`es/full/all/es5`	`181233095` ns/iter (`± 19041028`)	`211399283` ns/iter (`± 7327180`)	`0.86`
`es/full/all/es2015`	`146046126` ns/iter (`± 5716949`)	`170894992` ns/iter (`± 8554800`)	`0.85`
`es/full/all/es2016`	`154544399` ns/iter (`± 15929619`)	`169573948` ns/iter (`± 6334468`)	`0.91`
`es/full/all/es2017`	`153665769` ns/iter (`± 12731676`)	`168610335` ns/iter (`± 13425787`)	`0.91`
`es/full/all/es2018`	`146092101` ns/iter (`± 10370831`)	`165343930` ns/iter (`± 6897689`)	`0.88`
`es/full/all/es2019`	`138399647` ns/iter (`± 5247802`)	`164164489` ns/iter (`± 5571963`)	`0.84`
`es/full/all/es2020`	`134339039` ns/iter (`± 5818882`)	`158988979` ns/iter (`± 6146350`)	`0.84`
`es/full/parser`	`705046` ns/iter (`± 30302`)	`805844` ns/iter (`± 38088`)	`0.87`
`es/full/base/fixer`	`25879` ns/iter (`± 976`)	`29050` ns/iter (`± 1785`)	`0.89`
`es/full/base/resolver_and_hygiene`	`90517` ns/iter (`± 8647`)	`104876` ns/iter (`± 7312`)	`0.86`
`serialization of ast node`	`212` ns/iter (`± 7`)	`255` ns/iter (`± 18`)	`0.83`
`serialization of serde`	`218` ns/iter (`± 3`)	`245` ns/iter (`± 14`)	`0.89`