remove canonicalization of equality order

Author: evanw

internal/bundler/snapshots/snapshots_dce.txt

@@ -358,22 +358,14 @@ TestDCETypeOfEqualsStringGuardCondition
  var keep_1 = typeof x != "object" && x;
  var keep_1 = typeof x === "object" || x;
  var keep_1 = typeof x == "object" || x;
- var keep_1 = typeof x !== "object" ? x : null;
- var keep_1 = typeof x != "object" ? x : null;
- var keep_1 = typeof x === "object" ? null : x;
- var keep_1 = typeof x == "object" ? null : x;
- var keep_1 = typeof x !== "object" && x;
- var keep_1 = typeof x != "object" && x;
- var keep_1 = typeof x === "object" || x;
- var keep_1 = typeof x == "object" || x;
- var keep_2 = typeof x !== "undefined" ? y : null;
- var keep_2 = typeof x != "undefined" ? y : null;
- var keep_2 = typeof x === "undefined" ? null : y;
- var keep_2 = typeof x == "undefined" ? null : y;
- var keep_2 = typeof x !== "undefined" && y;
- var keep_2 = typeof x != "undefined" && y;
- var keep_2 = typeof x === "undefined" || y;
- var keep_2 = typeof x == "undefined" || y;
+ var keep_1 = "object" !== typeof x ? x : null;
+ var keep_1 = "object" != typeof x ? x : null;
+ var keep_1 = "object" === typeof x ? null : x;
+ var keep_1 = "object" == typeof x ? null : x;
+ var keep_1 = "object" !== typeof x && x;
+ var keep_1 = "object" != typeof x && x;
+ var keep_1 = "object" === typeof x || x;
+ var keep_1 = "object" == typeof x || x;
  var keep_2 = typeof x !== "undefined" ? y : null;
  var keep_2 = typeof x != "undefined" ? y : null;
  var keep_2 = typeof x === "undefined" ? null : y;
@@ -382,6 +374,14 @@ TestDCETypeOfEqualsStringGuardCondition
  var keep_2 = typeof x != "undefined" && y;
  var keep_2 = typeof x === "undefined" || y;
  var keep_2 = typeof x == "undefined" || y;
+ var keep_2 = "undefined" !== typeof x ? y : null;
+ var keep_2 = "undefined" != typeof x ? y : null;
+ var keep_2 = "undefined" === typeof x ? null : y;
+ var keep_2 = "undefined" == typeof x ? null : y;
+ var keep_2 = "undefined" !== typeof x && y;
+ var keep_2 = "undefined" != typeof x && y;
+ var keep_2 = "undefined" === typeof x || y;
+ var keep_2 = "undefined" == typeof x || y;
  var keep_3 = typeof x !== "undefined" ? null : x;
  var keep_3 = typeof x != "undefined" ? null : x;
  var keep_3 = typeof x === "undefined" ? x : null;
@@ -390,14 +390,14 @@ TestDCETypeOfEqualsStringGuardCondition
  var keep_3 = typeof x != "undefined" || x;
  var keep_3 = typeof x === "undefined" && x;
  var keep_3 = typeof x == "undefined" && x;
- var keep_3 = typeof x !== "undefined" ? null : x;
- var keep_3 = typeof x != "undefined" ? null : x;
- var keep_3 = typeof x === "undefined" ? x : null;
- var keep_3 = typeof x == "undefined" ? x : null;
- var keep_3 = typeof x !== "undefined" || x;
- var keep_3 = typeof x != "undefined" || x;
- var keep_3 = typeof x === "undefined" && x;
- var keep_3 = typeof x == "undefined" && x;
+ var keep_3 = "undefined" !== typeof x ? null : x;
+ var keep_3 = "undefined" != typeof x ? null : x;
+ var keep_3 = "undefined" === typeof x ? x : null;
+ var keep_3 = "undefined" == typeof x ? x : null;
+ var keep_3 = "undefined" !== typeof x || x;
+ var keep_3 = "undefined" != typeof x || x;
+ var keep_3 = "undefined" === typeof x && x;
+ var keep_3 = "undefined" == typeof x && x;
 })();
 
 ================================================================================

internal/js_parser/js_parser.go

@@ -9666,7 +9666,7 @@ func (p *parser) visitAndAppendStmt(stmts []js_ast.Stmt, stmt js_ast.Stmt) []js_
 if c.ValueOrNil.Data != nil {
 c.ValueOrNil = p.visitExpr(c.ValueOrNil)
 p.warnAboutEqualityCheck("case", c.ValueOrNil, c.ValueOrNil.Loc)
-p.warnAboutTypeofAndString(s.Test, c.ValueOrNil)
+p.warnAboutTypeofAndString(s.Test, c.ValueOrNil, onlyCheckOriginalOrder)
 }
 c.Body = p.visitStmts(c.Body, stmtsNormal)
 
@@ -10820,7 +10820,20 @@ func (p *parser) checkForUnrepresentableIdentifier(loc logger.Loc, name string)
 }
 }
 
-func (p *parser) warnAboutTypeofAndString(a js_ast.Expr, b js_ast.Expr) {
+type typeofStringOrder uint8
+
+const (
+onlyCheckOriginalOrder typeofStringOrder = iota
+checkBothOrders
+)
+
+func (p *parser) warnAboutTypeofAndString(a js_ast.Expr, b js_ast.Expr, order typeofStringOrder) {
+if order == checkBothOrders {
+if _, ok := a.Data.(*js_ast.EString); ok {
+a, b = b, a
+}
+}
+
 if typeof, ok := a.Data.(*js_ast.EUnary); ok && typeof.Op == js_ast.UnOpTypeof {
 if str, ok := b.Data.(*js_ast.EString); ok {
 value := helpers.UTF16ToString(str.Value)
@@ -10856,15 +10869,22 @@ func canChangeStrictToLoose(a js_ast.Expr, b js_ast.Expr) bool {
 }
 
 func (p *parser) maybeSimplifyEqualityComparison(loc logger.Loc, e *js_ast.EBinary) (js_ast.Expr, bool) {
+value, primitive := e.Left, e.Right
+
+// Detect when the primitive comes first and flip the order of our checks
+if isPrimitiveLiteral(value.Data) {
+value, primitive = primitive, value
+}
+
 // "!x === true" => "!x"
 // "!x === false" => "!!x"
 // "!x !== true" => "!!x"
 // "!x !== false" => "!x"
-if boolean, ok := e.Right.Data.(*js_ast.EBoolean); ok && js_ast.KnownPrimitiveType(e.Left) == js_ast.PrimitiveBoolean {
+if boolean, ok := primitive.Data.(*js_ast.EBoolean); ok && js_ast.KnownPrimitiveType(value) == js_ast.PrimitiveBoolean {
 if boolean.Value == (e.Op == js_ast.BinOpLooseNe || e.Op == js_ast.BinOpStrictNe) {
-return js_ast.Not(e.Left), true
+return js_ast.Not(value), true
 } else {
-return e.Left, true
+return value, true
 }
 }
 
@@ -10875,17 +10895,18 @@ func (p *parser) maybeSimplifyEqualityComparison(loc logger.Loc, e *js_ast.EBina
 // return something random. The only case of this happening was Internet
 // Explorer returning "unknown" for some objects, which messes with this
 // optimization. So we don't do this when targeting Internet Explorer.
-if typeof, ok := e.Left.Data.(*js_ast.EUnary); ok && typeof.Op == js_ast.UnOpTypeof {
-if str, ok := e.Right.Data.(*js_ast.EString); ok && helpers.UTF16EqualsString(str.Value, "undefined") {
+if typeof, ok := value.Data.(*js_ast.EUnary); ok && typeof.Op == js_ast.UnOpTypeof {
+if str, ok := primitive.Data.(*js_ast.EString); ok && helpers.UTF16EqualsString(str.Value, "undefined") {
+flip := value == e.Right
 op := js_ast.BinOpLt
-if e.Op == js_ast.BinOpLooseEq || e.Op == js_ast.BinOpStrictEq {
+if (e.Op == js_ast.BinOpLooseEq || e.Op == js_ast.BinOpStrictEq) != flip {
 op = js_ast.BinOpGt
 }
-return js_ast.Expr{Loc: loc, Data: &js_ast.EBinary{
-Op: op,
-Left: e.Left,
-Right: js_ast.Expr{Loc: e.Right.Loc, Data: &js_ast.EString{Value: []uint16{'u'}}},
-}}, true
+primitive.Data = &js_ast.EString{Value: []uint16{'u'}}
+if flip {
+value, primitive = primitive, value
+}
+return js_ast.Expr{Loc: loc, Data: &js_ast.EBinary{Op: op, Left: value, Right: primitive}}, true
 }
 }
 }
@@ -11477,18 +11498,29 @@ func stringToEquivalentNumberValue(value []uint16) (float64, bool) {
 func isBinaryNullAndUndefined(left js_ast.Expr, right js_ast.Expr, op js_ast.OpCode) (js_ast.Expr, js_ast.Expr, bool) {
 if a, ok := left.Data.(*js_ast.EBinary); ok && a.Op == op {
 if b, ok := right.Data.(*js_ast.EBinary); ok && b.Op == op {
-if idA, ok := a.Left.Data.(*js_ast.EIdentifier); ok {
-if idB, ok := b.Left.Data.(*js_ast.EIdentifier); ok && idA.Ref == idB.Ref {
+idA, eqA := a.Left, a.Right
+idB, eqB := b.Left, b.Right
+
+// Detect when the identifier comes second and flip the order of our checks
+if _, ok := eqA.Data.(*js_ast.EIdentifier); ok {
+idA, eqA = eqA, idA
+}
+if _, ok := eqB.Data.(*js_ast.EIdentifier); ok {
+idB, eqB = eqB, idB
+}
+
+if idA, ok := idA.Data.(*js_ast.EIdentifier); ok {
+if idB, ok := idB.Data.(*js_ast.EIdentifier); ok && idA.Ref == idB.Ref {
 // "a === null || a === void 0"
-if _, ok := a.Right.Data.(*js_ast.ENull); ok {
-if _, ok := b.Right.Data.(*js_ast.EUndefined); ok {
+if _, ok := eqA.Data.(*js_ast.ENull); ok {
+if _, ok := eqB.Data.(*js_ast.EUndefined); ok {
 return a.Left, a.Right, true
 }
 }
 
 // "a === void 0 || a === null"
-if _, ok := a.Right.Data.(*js_ast.EUndefined); ok {
-if _, ok := b.Right.Data.(*js_ast.ENull); ok {
+if _, ok := eqA.Data.(*js_ast.EUndefined); ok {
+if _, ok := eqB.Data.(*js_ast.ENull); ok {
 return b.Left, b.Right, true
 }
 }
@@ -12164,16 +12196,6 @@ func (p *parser) visitExprInOut(expr js_ast.Expr, in exprIn) (js_ast.Expr, exprO
 }
 p.fnOnlyDataVisit.silenceWarningAboutThisBeingUndefined = oldSilenceWarningAboutThisBeingUndefined
 
-// Always put constants on the right for equality comparisons to help
-// reduce the number of cases we have to check during pattern matching. We
-// can only reorder expressions that do not have any side effects.
-switch e.Op {
-case js_ast.BinOpLooseEq, js_ast.BinOpLooseNe, js_ast.BinOpStrictEq, js_ast.BinOpStrictNe:
-if isPrimitiveLiteral(e.Left.Data) && !isPrimitiveLiteral(e.Right.Data) {
-e.Left, e.Right = e.Right, e.Left
-}
-}
-
 // Post-process the binary expression
 switch e.Op {
 case js_ast.BinOpComma:
@@ -12200,11 +12222,13 @@ func (p *parser) visitExprInOut(expr js_ast.Expr, in exprIn) (js_ast.Expr, exprO
 if !p.warnAboutEqualityCheck("==", e.Left, afterOpLoc) {
 p.warnAboutEqualityCheck("==", e.Right, afterOpLoc)
 }
-p.warnAboutTypeofAndString(e.Left, e.Right)
+p.warnAboutTypeofAndString(e.Left, e.Right, checkBothOrders)
 
 if p.options.minifySyntax {
 // "x == void 0" => "x == null"
-if _, ok := e.Right.Data.(*js_ast.EUndefined); ok {
+if _, ok := e.Left.Data.(*js_ast.EUndefined); ok {
+e.Left.Data = js_ast.ENullShared
+} else if _, ok := e.Right.Data.(*js_ast.EUndefined); ok {
 e.Right.Data = js_ast.ENullShared
 }
 
@@ -12221,7 +12245,7 @@ func (p *parser) visitExprInOut(expr js_ast.Expr, in exprIn) (js_ast.Expr, exprO
 if !p.warnAboutEqualityCheck("===", e.Left, afterOpLoc) {
 p.warnAboutEqualityCheck("===", e.Right, afterOpLoc)
 }
-p.warnAboutTypeofAndString(e.Left, e.Right)
+p.warnAboutTypeofAndString(e.Left, e.Right, checkBothOrders)
 
 if p.options.minifySyntax {
 // "typeof x === 'undefined'" => "typeof x == 'undefined'"
@@ -12242,11 +12266,13 @@ func (p *parser) visitExprInOut(expr js_ast.Expr, in exprIn) (js_ast.Expr, exprO
 if !p.warnAboutEqualityCheck("!=", e.Left, afterOpLoc) {
 p.warnAboutEqualityCheck("!=", e.Right, afterOpLoc)
 }
-p.warnAboutTypeofAndString(e.Left, e.Right)
+p.warnAboutTypeofAndString(e.Left, e.Right, checkBothOrders)
 
 if p.options.minifySyntax {
 // "x != void 0" => "x != null"
-if _, ok := e.Right.Data.(*js_ast.EUndefined); ok {
+if _, ok := e.Left.Data.(*js_ast.EUndefined); ok {
+e.Left.Data = js_ast.ENullShared
+} else if _, ok := e.Right.Data.(*js_ast.EUndefined); ok {
 e.Right.Data = js_ast.ENullShared
 }
 
@@ -12263,7 +12289,7 @@ func (p *parser) visitExprInOut(expr js_ast.Expr, in exprIn) (js_ast.Expr, exprO
 if !p.warnAboutEqualityCheck("!==", e.Left, afterOpLoc) {
 p.warnAboutEqualityCheck("!==", e.Right, afterOpLoc)
 }
-p.warnAboutTypeofAndString(e.Left, e.Right)
+p.warnAboutTypeofAndString(e.Left, e.Right, checkBothOrders)
 
 if p.options.minifySyntax {
 // "typeof x !== 'undefined'" => "typeof x != 'undefined'"

internal/js_parser/js_parser_test.go

@@ -3172,20 +3172,20 @@ func TestMangleIf(t *testing.T) {
 
 expectPrintedMangle(t, "let b; a = null == b ? c : b", "let b;\na = b ?? c;\n")
 expectPrintedMangle(t, "let b; a = null != b ? b : c", "let b;\na = b ?? c;\n")
-expectPrintedMangle(t, "let b; a = null == b ? b : c", "let b;\na = b == null ? b : c;\n")
-expectPrintedMangle(t, "let b; a = null != b ? c : b", "let b;\na = b != null ? c : b;\n")
+expectPrintedMangle(t, "let b; a = null == b ? b : c", "let b;\na = null == b ? b : c;\n")
+expectPrintedMangle(t, "let b; a = null != b ? c : b", "let b;\na = null != b ? c : b;\n")
 
 // Don't do this if the condition has side effects
 expectPrintedMangle(t, "let b; a = b.x == null ? c : b.x", "let b;\na = b.x == null ? c : b.x;\n")
 expectPrintedMangle(t, "let b; a = b.x != null ? b.x : c", "let b;\na = b.x != null ? b.x : c;\n")
-expectPrintedMangle(t, "let b; a = null == b.x ? c : b.x", "let b;\na = b.x == null ? c : b.x;\n")
-expectPrintedMangle(t, "let b; a = null != b.x ? b.x : c", "let b;\na = b.x != null ? b.x : c;\n")
+expectPrintedMangle(t, "let b; a = null == b.x ? c : b.x", "let b;\na = null == b.x ? c : b.x;\n")
+expectPrintedMangle(t, "let b; a = null != b.x ? b.x : c", "let b;\na = null != b.x ? b.x : c;\n")
 
 // Don't do this for strict equality comparisons
 expectPrintedMangle(t, "let b; a = b === null ? c : b", "let b;\na = b === null ? c : b;\n")
 expectPrintedMangle(t, "let b; a = b !== null ? b : c", "let b;\na = b !== null ? b : c;\n")
-expectPrintedMangle(t, "let b; a = null === b ? c : b", "let b;\na = b === null ? c : b;\n")
-expectPrintedMangle(t, "let b; a = null !== b ? b : c", "let b;\na = b !== null ? b : c;\n")
+expectPrintedMangle(t, "let b; a = null === b ? c : b", "let b;\na = null === b ? c : b;\n")
+expectPrintedMangle(t, "let b; a = null !== b ? b : c", "let b;\na = null !== b ? b : c;\n")
 
 expectPrintedMangle(t, "let b; a = null === b || b === undefined ? c : b", "let b;\na = b ?? c;\n")
 expectPrintedMangle(t, "let b; a = b !== undefined && b !== null ? b : c", "let b;\na = b ?? c;\n")
@@ -3317,8 +3317,8 @@ func TestMangleOptionalChain(t *testing.T) {
 
 expectPrintedMangle(t, "a == null && a.b()", "a == null && a.b();\n")
 expectPrintedMangle(t, "a != null || a.b()", "a != null || a.b();\n")
-expectPrintedMangle(t, "null == a && a.b()", "a == null && a.b();\n")
-expectPrintedMangle(t, "null != a || a.b()", "a != null || a.b();\n")
+expectPrintedMangle(t, "null == a && a.b()", "null == a && a.b();\n")
+expectPrintedMangle(t, "null != a || a.b()", "null != a || a.b();\n")
 
 expectPrintedMangle(t, "x = a != null && a.b()", "x = a != null && a.b();\n")
 expectPrintedMangle(t, "x = a == null || a.b()", "x = a == null || a.b();\n")
@@ -3746,13 +3746,13 @@ func TestMangleTypeofIdentifier(t *testing.T) {
 func TestMangleTypeofEqualsUndefined(t *testing.T) {
 expectPrintedMangle(t, "return typeof x !== 'undefined'", "return typeof x < \"u\";\n")
 expectPrintedMangle(t, "return typeof x != 'undefined'", "return typeof x < \"u\";\n")
-expectPrintedMangle(t, "return 'undefined' !== typeof x", "return typeof x < \"u\";\n")
-expectPrintedMangle(t, "return 'undefined' != typeof x", "return typeof x < \"u\";\n")
+expectPrintedMangle(t, "return 'undefined' !== typeof x", "return \"u\" > typeof x;\n")
+expectPrintedMangle(t, "return 'undefined' != typeof x", "return \"u\" > typeof x;\n")
 
 expectPrintedMangle(t, "return typeof x === 'undefined'", "return typeof x > \"u\";\n")
 expectPrintedMangle(t, "return typeof x == 'undefined'", "return typeof x > \"u\";\n")
-expectPrintedMangle(t, "return 'undefined' === typeof x", "return typeof x > \"u\";\n")
-expectPrintedMangle(t, "return 'undefined' == typeof x", "return typeof x > \"u\";\n")
+expectPrintedMangle(t, "return 'undefined' === typeof x", "return \"u\" < typeof x;\n")
+expectPrintedMangle(t, "return 'undefined' == typeof x", "return \"u\" < typeof x;\n")
 }
 
 func TestMangleEquals(t *testing.T) {
@@ -3763,8 +3763,8 @@ func TestMangleEquals(t *testing.T) {
 
 expectPrintedMangle(t, "return typeof x === 'string'", "return typeof x == \"string\";\n")
 expectPrintedMangle(t, "return typeof x !== 'string'", "return typeof x != \"string\";\n")
-expectPrintedMangle(t, "return 'string' === typeof x", "return typeof x == \"string\";\n")
-expectPrintedMangle(t, "return 'string' !== typeof x", "return typeof x != \"string\";\n")
+expectPrintedMangle(t, "return 'string' === typeof x", "return \"string\" == typeof x;\n")
+expectPrintedMangle(t, "return 'string' !== typeof x", "return \"string\" != typeof x;\n")
 
 expectPrintedMangle(t, "return a === 0", "return a === 0;\n")
 expectPrintedMangle(t, "return a !== 0", "return a !== 0;\n")
@@ -3890,13 +3890,13 @@ func TestMangleNestedLogical(t *testing.T) {
 func TestMangleEqualsUndefined(t *testing.T) {
 expectPrintedMangle(t, "return a === void 0", "return a === void 0;\n")
 expectPrintedMangle(t, "return a !== void 0", "return a !== void 0;\n")
-expectPrintedMangle(t, "return void 0 === a", "return a === void 0;\n")
-expectPrintedMangle(t, "return void 0 !== a", "return a !== void 0;\n")
+expectPrintedMangle(t, "return void 0 === a", "return void 0 === a;\n")
+expectPrintedMangle(t, "return void 0 !== a", "return void 0 !== a;\n")
 
 expectPrintedMangle(t, "return a == void 0", "return a == null;\n")
 expectPrintedMangle(t, "return a != void 0", "return a != null;\n")
-expectPrintedMangle(t, "return void 0 == a", "return a == null;\n")
-expectPrintedMangle(t, "return void 0 != a", "return a != null;\n")
+expectPrintedMangle(t, "return void 0 == a", "return null == a;\n")
+expectPrintedMangle(t, "return void 0 != a", "return null != a;\n")
 
 expectPrintedMangle(t, "return a === null || a === undefined", "return a == null;\n")
 expectPrintedMangle(t, "return a === null || a !== undefined", "return a === null || a !== void 0;\n")