[CFE] Option to report error on unevaluated constants.

Fixes dart-lang/sdk#36565

Change-Id: I011e4b5242a02e06392af01ad77615c694fb62ba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/99121
Auto-Submit: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Aske Simon Christensen <askesc@google.com>

Author: askeksa

pkg/front_end/lib/src/api_prototype/compiler_options.dart

@@ -134,6 +134,11 @@ class CompilerOptions {
   /// unevaluated and can be evaluated by a constant evaluator later.
   Map<String, String> environmentDefines = null;
 
+  /// Report an error if a constant could not be evaluated (either because it
+  /// is an environment constant and no environment was specified, or because
+  /// it refers to a constructor or variable initializer that is not available).
+  bool errorOnUnevaluatedConstant = false;
+
   /// The target platform that will consume the compiled code.
   ///
   /// Used to provide platform-specific details to the compiler like:

pkg/front_end/lib/src/base/processed_options.dart

@@ -184,6 +184,8 @@ class ProcessedOptions {
 
   final Map<String, String> environmentDefines;
 
+  bool get errorOnUnevaluatedConstant => _raw.errorOnUnevaluatedConstant;
+
   /// Initializes a [ProcessedOptions] object wrapping the given [rawOptions].
   ProcessedOptions({CompilerOptions options, List<Uri> inputs, this.output})
       : this._raw = options ?? new CompilerOptions(),

pkg/front_end/lib/src/fasta/fasta_codes_generated.dart

@@ -1634,6 +1634,14 @@ const MessageCode messageConstEvalNullValue = const MessageCode(
     analyzerCodes: <String>["CONST_EVAL_THROWS_EXCEPTION"],
     message: r"""Null value during constant evaluation.""");
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeConstEvalUnevaluated = messageConstEvalUnevaluated;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageConstEvalUnevaluated = const MessageCode(
+    "ConstEvalUnevaluated",
+    message: r"""Could not evaluate constant expression.""");
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<
     Message Function(

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

@@ -45,6 +45,7 @@ import '../fasta_codes.dart'
         messageConstEvalNotListOrSetInSpread,
         messageConstEvalNotMapInSpread,
         messageConstEvalNullValue,
+        messageConstEvalUnevaluated,
         noLength,
         templateConstEvalDeferredLibrary,
         templateConstEvalDuplicateElement,
@@ -83,6 +84,7 @@ Component transformComponent(Component component, ConstantsBackend backend,
     bool enableAsserts: false,
     bool evaluateAnnotations: true,
     bool desugarSets: false,
+    bool errorOnUnevaluatedConstant: false,
     CoreTypes coreTypes,
     ClassHierarchy hierarchy}) {
   coreTypes ??= new CoreTypes(component);
@@ -95,6 +97,7 @@ Component transformComponent(Component component, ConstantsBackend backend,
       keepFields: keepFields,
       enableAsserts: enableAsserts,
       desugarSets: desugarSets,
+      errorOnUnevaluatedConstant: errorOnUnevaluatedConstant,
       evaluateAnnotations: evaluateAnnotations);
   return component;
 }
@@ -109,6 +112,7 @@ void transformLibraries(
     bool keepVariables: false,
     bool evaluateAnnotations: true,
     bool desugarSets: false,
+    bool errorOnUnevaluatedConstant: false,
     bool enableAsserts: false}) {
   final ConstantsTransformer constantsTransformer = new ConstantsTransformer(
       backend,
@@ -117,6 +121,7 @@ void transformLibraries(
       keepVariables,
       evaluateAnnotations,
       desugarSets,
+      errorOnUnevaluatedConstant,
       typeEnvironment,
       enableAsserts,
       errorReporter);
@@ -150,6 +155,7 @@ class ConstantsTransformer extends Transformer {
   final bool keepVariables;
   final bool evaluateAnnotations;
   final bool desugarSets;
+  final bool errorOnUnevaluatedConstant;
 
   ConstantsTransformer(
       ConstantsBackend backend,
@@ -158,12 +164,14 @@ class ConstantsTransformer extends Transformer {
       this.keepVariables,
       this.evaluateAnnotations,
       this.desugarSets,
+      this.errorOnUnevaluatedConstant,
       this.typeEnvironment,
       bool enableAsserts,
       ErrorReporter errorReporter)
       : constantEvaluator = new ConstantEvaluator(backend, environmentDefines,
             typeEnvironment, enableAsserts, errorReporter,
-            desugarSets: desugarSets);
+            desugarSets: desugarSets,
+            errorOnUnevaluatedConstant: errorOnUnevaluatedConstant);
 
   // Transform the library/class members:
 
@@ -454,6 +462,7 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
   final ConstantsBackend backend;
   final NumberSemantics numberSemantics;
   Map<String, String> environmentDefines;
+  final bool errorOnUnevaluatedConstant;
   final CoreTypes coreTypes;
   final TypeEnvironment typeEnvironment;
   final bool enableAsserts;
@@ -490,7 +499,7 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
 
   ConstantEvaluator(this.backend, this.environmentDefines, this.typeEnvironment,
       this.enableAsserts, this.errorReporter,
-      {this.desugarSets = false})
+      {this.desugarSets = false, this.errorOnUnevaluatedConstant = false})
       : numberSemantics = backend.numberSemantics,
         coreTypes = typeEnvironment.coreTypes,
         canonicalizationCache = <Constant, Constant>{},
@@ -539,7 +548,11 @@ class ConstantEvaluator extends RecursiveVisitor<Constant> {
     seenUnevaluatedChild = false;
     lazyDepth = 0;
     try {
-      return _evaluateSubexpression(node);
+      Constant result = _evaluateSubexpression(node);
+      if (errorOnUnevaluatedConstant && result is UnevaluatedConstant) {
+        return report(node, messageConstEvalUnevaluated);
+      }
+      return result;
     } on _AbortDueToError catch (e) {
       final Uri uri = getFileUri(e.node);
       final int fileOffset = getFileOffset(uri, e.node);

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

@@ -136,6 +136,9 @@ class KernelTarget extends TargetImplementation {
   final Map<String, String> environmentDefines =
       CompilerContext.current.options.environmentDefines;
 
+  final bool errorOnUnevaluatedConstant =
+      CompilerContext.current.options.errorOnUnevaluatedConstant;
+
   final bool enableAsserts = CompilerContext.current.options.enableAsserts;
 
   final List<Object> clonedFormals = <Object>[];
@@ -777,7 +780,8 @@ class KernelTarget extends TargetImplementation {
           environment,
           new KernelConstantErrorReporter(loader),
           enableAsserts: enableAsserts,
-          desugarSets: !backendTarget.supportsSetLiterals);
+          desugarSets: !backendTarget.supportsSetLiterals,
+          errorOnUnevaluatedConstant: errorOnUnevaluatedConstant);
       ticker.logMs("Evaluated constants");
     }
     backendTarget.performModularTransformationsOnLibraries(

pkg/front_end/messages.status

@@ -93,6 +93,8 @@ ConstEvalNonConstantVariableGet/example: Fail
 ConstEvalNotListOrSetInSpread/example: Fail
 ConstEvalNotMapInSpread/example: Fail
 ConstEvalNullValue/example: Fail
+ConstEvalUnevaluated/analyzerCode: Fail
+ConstEvalUnevaluated/example: Fail
 ConstEvalZeroDivisor/example: Fail
 ConstFieldWithoutInitializer/example: Fail
 ConstructorNotFound/example: Fail

pkg/front_end/messages.yaml

@@ -193,6 +193,9 @@ ConstEvalIterationInConstMap:
   template: "Iteration can't be used in a constant map."
   analyzerCode: NON_CONSTANT_MAP_ELEMENT
 
+ConstEvalUnevaluated:
+  template: "Could not evaluate constant expression."
+
 NotConstantExpression:
   template: "#string is not a constant expression."
   analyzerCode: NOT_CONSTANT_EXPRESSION