[CFE] Constant transformation for expression compilation

Fixes #42240

Change-Id: Idc75e99aed6acbb67755c77faa1904183a630f91
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/153355
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/front_end/lib/src/fasta/kernel/constant_evaluator.dart

@@ -127,6 +127,32 @@ void transformLibraries(
   }
 }
 
+void transformProcedure(
+    Procedure procedure,
+    ConstantsBackend backend,
+    Map<String, String> environmentDefines,
+    TypeEnvironment typeEnvironment,
+    ErrorReporter errorReporter,
+    EvaluationMode evaluationMode,
+    {bool keepFields: true,
+    bool evaluateAnnotations: true,
+    bool desugarSets: false,
+    bool enableTripleShift: false,
+    bool errorOnUnevaluatedConstant: false}) {
+  final ConstantsTransformer constantsTransformer = new ConstantsTransformer(
+      backend,
+      environmentDefines,
+      keepFields,
+      evaluateAnnotations,
+      desugarSets,
+      enableTripleShift,
+      errorOnUnevaluatedConstant,
+      typeEnvironment,
+      errorReporter,
+      evaluationMode);
+  constantsTransformer.visitProcedure(procedure);
+}
+
 enum EvaluationMode {
   weak,
   agnostic,

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

@@ -122,7 +122,7 @@ import '../target_implementation.dart' show TargetImplementation;
 import '../uri_translator.dart' show UriTranslator;
 
 import 'constant_evaluator.dart' as constants
-    show EvaluationMode, transformLibraries;
+    show EvaluationMode, transformLibraries, transformProcedure;
 
 import 'kernel_constants.dart' show KernelConstantErrorReporter;
 
@@ -1092,26 +1092,7 @@ class KernelTarget extends TargetImplementation {
 
     TypeEnvironment environment =
         new TypeEnvironment(loader.coreTypes, loader.hierarchy);
-    constants.EvaluationMode evaluationMode;
-    // If nnbd is not enabled we will use weak evaluation mode. This is needed
-    // because the SDK might be agnostic and therefore needs to be weakened
-    // for legacy mode.
-    assert(
-        isExperimentEnabledGlobally(ExperimentalFlag.nonNullable) ||
-            loader.nnbdMode == NnbdMode.Weak,
-        "Non-weak nnbd mode found without experiment enabled: "
-        "${loader.nnbdMode}.");
-    switch (loader.nnbdMode) {
-      case NnbdMode.Weak:
-        evaluationMode = constants.EvaluationMode.weak;
-        break;
-      case NnbdMode.Strong:
-        evaluationMode = constants.EvaluationMode.strong;
-        break;
-      case NnbdMode.Agnostic:
-        evaluationMode = constants.EvaluationMode.agnostic;
-        break;
-    }
+    constants.EvaluationMode evaluationMode = _getConstantEvaluationMode();
 
     constants.transformLibraries(
         loader.libraries,
@@ -1141,11 +1122,52 @@ class KernelTarget extends TargetImplementation {
   ChangedStructureNotifier get changedStructureNotifier => null;
 
   void runProcedureTransformations(Procedure procedure) {
+    TypeEnvironment environment =
+        new TypeEnvironment(loader.coreTypes, loader.hierarchy);
+    constants.EvaluationMode evaluationMode = _getConstantEvaluationMode();
+
+    constants.transformProcedure(
+        procedure,
+        backendTarget.constantsBackend(loader.coreTypes),
+        environmentDefines,
+        environment,
+        new KernelConstantErrorReporter(loader),
+        evaluationMode,
+        desugarSets: !backendTarget.supportsSetLiterals,
+        enableTripleShift:
+            isExperimentEnabledGlobally(ExperimentalFlag.tripleShift),
+        errorOnUnevaluatedConstant: errorOnUnevaluatedConstant);
+    ticker.logMs("Evaluated constants");
+
     backendTarget.performTransformationsOnProcedure(
         loader.coreTypes, loader.hierarchy, procedure,
         logger: (String msg) => ticker.logMs(msg));
   }
 
+  constants.EvaluationMode _getConstantEvaluationMode() {
+    constants.EvaluationMode evaluationMode;
+    // If nnbd is not enabled we will use weak evaluation mode. This is needed
+    // because the SDK might be agnostic and therefore needs to be weakened
+    // for legacy mode.
+    assert(
+        isExperimentEnabledGlobally(ExperimentalFlag.nonNullable) ||
+            loader.nnbdMode == NnbdMode.Weak,
+        "Non-weak nnbd mode found without experiment enabled: "
+        "${loader.nnbdMode}.");
+    switch (loader.nnbdMode) {
+      case NnbdMode.Weak:
+        evaluationMode = constants.EvaluationMode.weak;
+        break;
+      case NnbdMode.Strong:
+        evaluationMode = constants.EvaluationMode.strong;
+        break;
+      case NnbdMode.Agnostic:
+        evaluationMode = constants.EvaluationMode.agnostic;
+        break;
+    }
+    return evaluationMode;
+  }
+
   void verify() {
     // TODO(ahe): How to handle errors.
     verifyComponent(component);

pkg/front_end/test/fasta/expression_suite.dart

@@ -113,7 +113,9 @@ class CompilationResult {
     if (compiledProcedure == null) {
       buffer.write("<no procedure>");
     } else {
-      new Printer(buffer).visitProcedure(compiledProcedure);
+      Printer printer = new Printer(buffer);
+      printer.visitProcedure(compiledProcedure);
+      printer.writeConstantTable(new Component());
     }
     Uri base = entryPoint.resolve(".");
     return "$buffer".replaceAll("$base", "org-dartlang-testcase:///");

pkg/front_end/testcases/expression/const_usage.expression.yaml

@@ -0,0 +1,9 @@
+# Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+entry_point: "main.dart"
+definitions: []
+position: "main.dart"
+expression: |
+  const42.x

pkg/front_end/testcases/expression/const_usage.expression.yaml.expect

@@ -0,0 +1,8 @@
+Errors: {
+}
+method /* from org-dartlang-debug:synthetic_debug_expression */ debugExpr() → dynamic
+  return (#C2).{main::ConstClass::x};
+constants  {
+  #C1 = 42
+  #C2 = main::ConstClass {x:#C1}
+}

pkg/front_end/testcases/expression/const_usage_class.expression.yaml

@@ -0,0 +1,9 @@
+# Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE file.
+
+entry_point: "main.dart"
+definitions: []
+position: "main.dart#ConstClass"
+expression: |
+  classConst42.x

pkg/front_end/testcases/expression/const_usage_class.expression.yaml.expect

@@ -0,0 +1,8 @@
+Errors: {
+}
+method /* from org-dartlang-debug:synthetic_debug_expression */ debugExpr() → dynamic
+  return (#C2).{main::ConstClass::x};
+constants  {
+  #C1 = 42
+  #C2 = main::ConstClass {x:#C1}
+}

pkg/front_end/testcases/expression/lib_ctor.expression.yaml.expect

@@ -3,5 +3,9 @@ Errors: {
 method /* from org-dartlang-debug:synthetic_debug_expression */ debugExpr() → dynamic
   return () → dart.core::Null? {
     new main::A::•<dynamic>();
-    const main::A::•<dynamic>();
+    #C2;
   };
+constants  {
+  #C1 = 0
+  #C2 = main::A<dynamic> {_priv:#C1}
+}

pkg/front_end/testcases/expression/main.dart

@@ -14,6 +14,14 @@ int _privateToplevel(int x) => x + 1;
 int globalVar = 6;
 int _globalPrivate = 7;
 
+const ConstClass const42 = ConstClass(42);
+
+class ConstClass {
+  static const ConstClass classConst42 = ConstClass(42);
+  final int x;
+  const ConstClass(this.x);
+}
+
 class A<T> {
   const A();
   static int doit(int x) => x + 1;

pkg/frontend_server/test/src/expression_compiler_test.dart

@@ -1164,7 +1164,7 @@ int main() {
           expression: 'const MyClass(1)',
           expectedResult: '''
           (function(p) {
-            return dart.const(new foo.MyClass.new(1));
+            return C0 || CT.C0;
           }(
           1
           ))