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[tfa] Propagate int and string constants in conditionals
When comparing a value against a literal or constant: if (x == literal) { ... } if (x == constant) { ... } Allow propagating the value if the LHS type is `int` or `String`, as those types don't have identity. Previously we would propagate the values if the RHS is a literal (not constant). Constants would only be propagated if the LHS type does not override `operator ==`. Because `int` and `String` don't have identity, they can be propagated when they're constants even though they override `operator ==`. Tested: Added new TFA transformer test. Change-Id: I3c150ffae39bfbc06992f666ffec7bab1d1c52d7 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/403987 Commit-Queue: Ömer Ağacan <[email protected]> Reviewed-by: Martin Kustermann <[email protected]> Reviewed-by: Alexander Markov <[email protected]>
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3 files changed

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lines changed

‎pkg/vm/lib/transformations/type_flow/summary_collector.dart‎

Lines changed: 12 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1578,10 +1578,20 @@ class SummaryCollector extends RecursiveResultVisitor<TypeExpr?> {
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} else if (node is EqualsCall && node.left is VariableGet) {
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final lhs = node.left as VariableGet;
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final rhs = node.right;
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if ((rhs is IntLiteral &&
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bool isIntConstant(Expression expr) => switch (expr) {
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IntLiteral() => true,
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ConstantExpression(constant: IntConstant()) => true,
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_ => false
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};
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bool isStringConstant(Expression expr) => switch (expr) {
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StringLiteral() => true,
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ConstantExpression(constant: StringConstant()) => true,
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_ => false
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};
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if ((isIntConstant(rhs) &&
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_isSubtype(lhs.variable.type,
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_environment.coreTypes.intNullableRawType)) ||
1584-
(rhs is StringLiteral &&
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(isStringConstant(rhs) &&
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target.canInferStringClassAfterEqualityComparison &&
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_isSubtype(lhs.variable.type,
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_environment.coreTypes.stringNullableRawType)) ||

‎pkg/vm/testcases/transformations/type_flow/transformer/const_prop_conditional.dart‎

Lines changed: 104 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,104 @@
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// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// Tests constant propagation inside considitonals.
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void testStringLiteral(String s) {
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print(s);
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}
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void testStringConstant(String s) {
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print(s);
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}
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void testIntLiteral(int i) {
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print(i);
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}
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void testIntConstant(int i) {
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print(i);
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}
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void testDefaultEq1(DefaultEq c) {
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print(c);
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}
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void testDefaultEq2(DefaultEq c) {
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print(c);
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}
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void testOverriddenEq1(OverriddenEq c) {
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print(c);
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}
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void testOverriddenEq2(OverriddenEq c) {
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print(c);
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}
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bool get runtimeTrue => int.parse('1') == 1;
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class DefaultEq {
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final int i;
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const DefaultEq(this.i);
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@override
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String toString() => 'DefaultEq(i=$i)';
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}
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class OverriddenEq {
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final int i;
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const OverriddenEq(this.i);
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@override
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bool operator ==(Object other) {
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return true;
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}
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@override
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String toString() => 'OverriddenEq(i=$i)';
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}
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void main() {
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final s1 = runtimeTrue ? "foo" : "bar";
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if (s1 == "foo") {
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testStringLiteral(s1);
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}
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final s2 = runtimeTrue ? "1234" : "asdf";
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const sConst = "1234";
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if (s2 == sConst) {
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testStringConstant(s2);
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}
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final i1 = runtimeTrue ? 123 : 456;
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if (i1 == 123) {
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testIntLiteral(i1);
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}
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final i2 = runtimeTrue ? 456 : 789;
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const iConst = 456;
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if (i2 == iConst) {
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testIntConstant(i2);
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}
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final c1 = runtimeTrue ? DefaultEq(1) : DefaultEq(2);
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if (c1 == const DefaultEq(1)) {
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testDefaultEq1(c1); // should propagate
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}
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if (c1 == sConst) {
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testDefaultEq2(c1); // OK to propagate as the branch won't be taken
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}
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final c2 = runtimeTrue ? OverriddenEq(1) : OverriddenEq(2);
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if (c2 == const OverriddenEq(1)) {
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testOverriddenEq1(c2); // should not propagate
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}
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if (c2 == sConst) {
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testOverriddenEq2(c2); // should not propagate
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}
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}

‎pkg/vm/testcases/transformations/type_flow/transformer/const_prop_conditional.dart.expect‎

Lines changed: 134 additions & 0 deletions
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@@ -0,0 +1,134 @@
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library #lib;
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import self as self;
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import "dart:core" as core;
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class DefaultEq extends core::Object /*hasConstConstructor*/ {
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[@vm.inferred-type.metadata=dart.core::_Smi]
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[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,getterSelectorId:1]
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[@vm.unboxing-info.metadata=()->i]
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final field core::int i;
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[@vm.unboxing-info.metadata=(i)->b]
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const constructor •([@vm.inferred-arg-type.metadata=dart.core::_Smi] core::int i) → self::DefaultEq
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: self::DefaultEq::i = i, super core::Object::•()
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;
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[@vm.inferred-return-type.metadata=!]
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[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:2,getterSelectorId:3]
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[@vm.unboxing-info.metadata=[!regcc]]
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method toString() → core::String
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return "DefaultEq(i=${[@vm.direct-call.metadata=#lib::DefaultEq.i] this.{self::DefaultEq::i}{core::int}})";
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}
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class OverriddenEq extends core::Object /*hasConstConstructor*/ {
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[@vm.inferred-type.metadata=dart.core::_Smi]
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[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasNonThisUses:false,hasTearOffUses:false,getterSelectorId:4]
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[@vm.unboxing-info.metadata=()->i]
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final field core::int i;
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[@vm.unboxing-info.metadata=(i)->b]
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const constructor •([@vm.inferred-arg-type.metadata=dart.core::_Smi] core::int i) → self::OverriddenEq
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: self::OverriddenEq::i = i, super core::Object::•()
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;
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[@vm.inferred-return-type.metadata=dart.core::bool]
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[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:5]
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[@vm.unboxing-info.metadata=[!regcc]]
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operator ==(core::Object other) → core::bool {
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return true;
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}
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[@vm.inferred-return-type.metadata=!]
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[@vm.procedure-attributes.metadata=methodOrSetterCalledDynamically:false,getterCalledDynamically:false,hasThisUses:false,hasTearOffUses:false,methodOrSetterSelectorId:2,getterSelectorId:3]
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[@vm.unboxing-info.metadata=[!regcc]]
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method toString() → core::String
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return "OverriddenEq(i=${[@vm.direct-call.metadata=#lib::OverriddenEq.i] this.{self::OverriddenEq::i}{core::int}})";
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testStringLiteral() → void {
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core::print(#C1);
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testStringConstant() → void {
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core::print(#C2);
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testIntLiteral() → void {
61+
core::print(#C3);
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testIntConstant() → void {
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core::print(#C4);
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testDefaultEq1() → void {
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core::print(#C6);
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testDefaultEq2() → void {
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throw "Attempt to execute code removed by Dart AOT compiler (TFA)";
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testOverriddenEq1([@vm.inferred-arg-type.metadata=#lib::OverriddenEq] self::OverriddenEq c) → void {
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core::print(c);
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}
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method testOverriddenEq2([@vm.inferred-arg-type.metadata=#lib::OverriddenEq] self::OverriddenEq c) → void {
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core::print(c);
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}
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[@vm.inferred-return-type.metadata=dart.core::bool]
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static get runtimeTrue() → core::bool
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return [@vm.direct-call.metadata=dart.core::_IntegerImplementation.==] [@vm.inferred-type.metadata=dart.core::bool (skip check)] [@vm.inferred-type.metadata=int] core::int::parse("1") =={core::num::==}{(core::Object) → core::bool} 1;
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[@vm.inferred-return-type.metadata=dart.core::Null? (value: null)]
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static method main() → void {
95+
final core::String s1 = [@vm.inferred-type.metadata=dart.core::bool] self::runtimeTrue ?{core::String} "foo" : "bar";
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if([@vm.inferred-type.metadata=dart.core::bool (receiver not int)] s1 =={core::String::==}{(core::Object) → core::bool} "foo") {
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self::testStringLiteral();
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}
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final core::String s2 = [@vm.inferred-type.metadata=dart.core::bool] self::runtimeTrue ?{core::String} "1234" : "asdf";
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if([@vm.inferred-type.metadata=dart.core::bool (receiver not int)] s2 =={core::String::==}{(core::Object) → core::bool} #C2) {
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self::testStringConstant();
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}
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final core::int i1 = [@vm.inferred-type.metadata=dart.core::bool] self::runtimeTrue ?{core::int} 123 : 456;
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if([@vm.direct-call.metadata=dart.core::_IntegerImplementation.==] [@vm.inferred-type.metadata=dart.core::bool (skip check)] i1 =={core::num::==}{(core::Object) → core::bool} 123) {
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self::testIntLiteral();
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}
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final core::int i2 = [@vm.inferred-type.metadata=dart.core::bool] self::runtimeTrue ?{core::int} 456 : 789;
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if([@vm.direct-call.metadata=dart.core::_IntegerImplementation.==] [@vm.inferred-type.metadata=dart.core::bool (skip check)] i2 =={core::num::==}{(core::Object) → core::bool} #C4) {
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self::testIntConstant();
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}
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final self::DefaultEq c1 = [@vm.inferred-type.metadata=dart.core::bool] self::runtimeTrue ?{self::DefaultEq} new self::DefaultEq::•(1) : new self::DefaultEq::•(2);
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if([@vm.direct-call.metadata=dart.core::Object.==] [@vm.inferred-type.metadata=dart.core::bool (skip check) (receiver not int)] c1 =={core::Object::==}{(core::Object) → core::bool} #C6) {
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self::testDefaultEq1();
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}
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if([@vm.direct-call.metadata=dart.core::Object.==] [@vm.inferred-type.metadata=dart.core::bool (skip check) (receiver not int)] c1 =={core::Object::==}{(core::Object) → core::bool} #C2) {
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self::testDefaultEq2();
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}
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final self::OverriddenEq c2 = [@vm.inferred-type.metadata=dart.core::bool] self::runtimeTrue ?{self::OverriddenEq} new self::OverriddenEq::•(1) : new self::OverriddenEq::•(2);
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if([@vm.direct-call.metadata=#lib::OverriddenEq.==] [@vm.inferred-type.metadata=dart.core::bool (skip check) (receiver not int)] c2 =={self::OverriddenEq::==}{(core::Object) → core::bool} #C7) {
120+
self::testOverriddenEq1(c2);
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}
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if([@vm.direct-call.metadata=#lib::OverriddenEq.==] [@vm.inferred-type.metadata=dart.core::bool (skip check) (receiver not int)] c2 =={self::OverriddenEq::==}{(core::Object) → core::bool} #C2) {
123+
self::testOverriddenEq2(c2);
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}
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}
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constants {
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#C1 = "foo"
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#C2 = "1234"
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#C3 = 123
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#C4 = 456
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#C5 = 1
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#C6 = self::DefaultEq {i:#C5}
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#C7 = self::OverriddenEq {i:#C5}
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}

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