Wrap field initializers copied by TFA in a FileUriExpression.

Before TFA runs, MixinFullResolution will clone a mixin's fields into the application classes for that mixin. The cloned Field on the application class will have a fileUri that refers to the original mixin file.

However, TFA then copies those fields into FieldInitializers which don't have a fileUri context and so the fileUri for the surrounding Constructor is used. This leaves expressions in the initializer with offsets relative to the mixin's file but in the context of the mixin application's file.

To fix this, we can wrap the initializer in a FileUriExpression referring to the original mixin class. We only do this if the field the initializer is copied from refers to a different file than the target constructor.

Also add handlers for FileUriExpressions to several visitors that don't already support this new AST node.

Change-Id: I47b0d48dfe87303949130a40216b199949cfa1d9
Tested: Existing test suite.
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/360420
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Ömer Ağacan <[email protected]>
Reviewed-by: Alexander Markov <[email protected]>

pkg/compiler/lib/src/inferrer/builder.dart

@@ -2246,6 +2246,11 @@ class KernelTypeGraphBuilder extends ir.VisitorDefault<TypeInformation?>
     return TypeInformationConstantVisitor(this, node)
         .visitConstant(node.constant);
   }
+
+  @override
+  TypeInformation visitFileUriExpression(ir.FileUriExpression node) {
+    return visit(node.expression)!;
+  }
 }
 
 class TypeInformationConstantVisitor

pkg/compiler/lib/src/ir/scope_visitor.dart

@@ -1443,6 +1443,11 @@ class ScopeModelBuilder extends ir.VisitorDefault<EvaluationComplexity>
     return const EvaluationComplexity.constant();
   }
 
+  @override
+  EvaluationComplexity visitFileUriExpression(ir.FileUriExpression node) {
+    return visitNode(node.expression);
+  }
+
   /// Returns true if the node is a field, or a constructor (factory or
   /// generative).
   bool _isFieldOrConstructor(ir.Node node) =>

pkg/compiler/lib/src/ssa/builder.dart

@@ -6228,6 +6228,11 @@ class KernelSsaGraphBuilder extends ir.VisitorDefault<void>
       ..cleanUp();
   }
 
+  @override
+  void visitFileUriExpression(ir.FileUriExpression node) {
+    node.expression.accept(this);
+  }
+
   bool _tryInlineMethod(
       FunctionEntity function,
       Selector? selector,

pkg/dart2wasm/lib/await_transformer.dart

@@ -767,6 +767,9 @@ class _ExpressionTransformer extends Transformer {
   @override
   TreeNode visitRethrow(Rethrow expr) => nullary(expr);
 
+  @override
+  TreeNode visitFileUriExpression(FileUriExpression expr) => unary(expr);
+
   @override
   TreeNode visitVariableGet(VariableGet expr) {
     Expression result = expr;

pkg/dart2wasm/lib/code_generator.dart

@@ -3160,6 +3160,12 @@ class CodeGenerator extends ExpressionVisitor1<w.ValueType, w.ValueType>
     return translator.topInfo.nullableType;
   }
 
+  @override
+  w.ValueType visitFileUriExpression(
+      FileUriExpression node, w.ValueType expectedType) {
+    return wrap(node.expression, expectedType);
+  }
+
   // Generates a function for a constructor's body, where the allocated struct
   // object is passed to this function.
   void generateConstructorBody(Reference target) {

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

@@ -2635,6 +2635,11 @@ class SummaryCollector extends RecursiveResultVisitor<TypeExpr?> {
     _visit(node.operand);
     return _staticType(node);
   }
+
+  @override
+  TypeExpr visitFileUriExpression(FileUriExpression node) {
+    return _visit(node.expression);
+  }
 }
 
 class RuntimeTypeTranslatorImpl

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

@@ -221,6 +221,14 @@ class MoveFieldInitializers {
         if (!isFirst) {
           initExpr = CloneVisitorNotMembers().clone(initExpr);
         }
+        if (c.fileUri != f.fileUri) {
+          if (initExpr is ConstantExpression) {
+            initExpr = FileUriConstantExpression(initExpr.constant,
+                type: initExpr.type, fileUri: f.fileUri);
+          } else {
+            initExpr = FileUriExpression(initExpr, f.fileUri);
+          }
+        }
         final Initializer newInit = initializedFields.contains(f)
             ? LocalInitializer(VariableDeclaration(null,
                 initializer: initExpr, isSynthesized: true))