[cfe] Support null-aware cascade

johnniwinther · commit-bot@chromium.org · commit 6e85f3337a29 · 2019-11-14T12:39:16.000Z
Change-Id: I1db4125b4469e6a8b6adc5ec6e4dcafc0a26da4a Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/124680 Reviewed-by: Aske Simon Christensen <askesc@google.com> Commit-Queue: Johnni Winther <johnniwinther@google.com>
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -1481,7 +1481,8 @@ class BodyBuilder extends ScopeListener<JumpTarget>
     } else {
       VariableDeclaration variable =
           forest.createVariableDeclarationForValue(expression);
-      push(new Cascade(variable)..fileOffset = expression.fileOffset);
+      push(new Cascade(variable, isNullAware: optional('?..', token))
+        ..fileOffset = expression.fileOffset);
       push(_createReadOnlyVariableAccess(
           variable, token, expression.fileOffset, null));
     }
diff --git a/pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart b/pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart
@@ -255,8 +255,19 @@ class InferenceVisitor
           createVariable(expressionResults[index].expression, const VoidType()),
           replacement);
     }
-    replacement = new Let(node.variable, replacement)
-      ..fileOffset = node.fileOffset;
+
+    if (node.isNullAware) {
+      Member equalsMember = inferrer
+          .findInterfaceMember(result.inferredType, equalsName, node.fileOffset)
+          .member;
+      NullAwareGuard nullAwareGuard = new NullAwareGuard(
+          node.variable, node.variable.fileOffset, equalsMember);
+      replacement =
+          nullAwareGuard.createExpression(result.inferredType, replacement);
+    } else {
+      replacement = new Let(node.variable, replacement)
+        ..fileOffset = node.fileOffset;
+    }
     return new ExpressionInferenceResult(result.inferredType, replacement);
   }
 
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_shadow_ast.dart
@@ -380,14 +380,16 @@ class Cascade extends InternalExpression {
   /// initializer;
   VariableDeclaration variable;
 
+  final bool isNullAware;
+
   /// The expressions performed on [variable].
   final List<Expression> expressions = <Expression>[];
 
   /// Creates a [Cascade] using [variable] as the cascade
   /// variable.  Caller is responsible for ensuring that [variable]'s
   /// initializer is the expression preceding the first `..` of the cascade
   /// expression.
-  Cascade(this.variable) {
+  Cascade(this.variable, {this.isNullAware}) : assert(isNullAware != null) {
     variable?.parent = this;
   }
 
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart
@@ -0,0 +1,19 @@
+// Copyright (c) 2019, 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.
+
+class Class {
+  Class method() => this;
+}
+
+extension Extension on Class {
+  Class extensionMethod() => this;
+}
+
+main() {
+  Class? c;
+  c?..method();
+  c?..method()..method();
+  c?..extensionMethod();
+  c?..extensionMethod()..extensionMethod();
+}
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.outline.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.outline.expect
@@ -0,0 +1,20 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    ;
+  method method() → self::Class
+    ;
+}
+extension Extension on self::Class {
+  method extensionMethod = self::Extension|extensionMethod;
+  tearoff extensionMethod = self::Extension|get#extensionMethod;
+}
+static method Extension|extensionMethod(final self::Class #this) → self::Class
+  ;
+static method Extension|get#extensionMethod(final self::Class #this) → () →* self::Class
+  return () → self::Class => self::Extension|extensionMethod(#this);
+static method main() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.expect
@@ -0,0 +1,26 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    : super core::Object::•()
+    ;
+  method method() → self::Class
+    return this;
+}
+extension Extension on self::Class {
+  method extensionMethod = self::Extension|extensionMethod;
+  tearoff extensionMethod = self::Extension|get#extensionMethod;
+}
+static method Extension|extensionMethod(final self::Class #this) → self::Class
+  return #this;
+static method Extension|get#extensionMethod(final self::Class #this) → () →* self::Class
+  return () → self::Class => self::Extension|extensionMethod(#this);
+static method main() → dynamic {
+  self::Class? c;
+  let final self::Class? #t1 = c in #t1.{core::Object::==}(null) ?{self::Class?} null : let final void #t2 = #t1.{self::Class::method}() in #t1;
+  let final self::Class? #t3 = c in #t3.{core::Object::==}(null) ?{self::Class?} null : let final void #t4 = #t3.{self::Class::method}() in let final void #t5 = #t3.{self::Class::method}() in #t3;
+  let final self::Class? #t6 = c in #t6.{core::Object::==}(null) ?{self::Class?} null : let final void #t7 = self::Extension|extensionMethod(#t6) in #t6;
+  let final self::Class? #t8 = c in #t8.{core::Object::==}(null) ?{self::Class?} null : let final void #t9 = self::Extension|extensionMethod(#t8) in let final void #t10 = self::Extension|extensionMethod(#t8) in #t8;
+}
diff --git a/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/null_shorting_cascade.dart.strong.transformed.expect
@@ -0,0 +1,26 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    : super core::Object::•()
+    ;
+  method method() → self::Class
+    return this;
+}
+extension Extension on self::Class {
+  method extensionMethod = self::Extension|extensionMethod;
+  tearoff extensionMethod = self::Extension|get#extensionMethod;
+}
+static method Extension|extensionMethod(final self::Class #this) → self::Class
+  return #this;
+static method Extension|get#extensionMethod(final self::Class #this) → () →* self::Class
+  return () → self::Class => self::Extension|extensionMethod(#this);
+static method main() → dynamic {
+  self::Class? c;
+  let final self::Class? #t1 = c in #t1.{core::Object::==}(null) ?{self::Class?} null : let final void #t2 = #t1.{self::Class::method}() in #t1;
+  let final self::Class? #t3 = c in #t3.{core::Object::==}(null) ?{self::Class?} null : let final void #t4 = #t3.{self::Class::method}() in let final void #t5 = #t3.{self::Class::method}() in #t3;
+  let final self::Class? #t6 = c in #t6.{core::Object::==}(null) ?{self::Class?} null : let final void #t7 = self::Extension|extensionMethod(#t6) in #t6;
+  let final self::Class? #t8 = c in #t8.{core::Object::==}(null) ?{self::Class?} null : let final void #t9 = self::Extension|extensionMethod(#t8) in let final void #t10 = self::Extension|extensionMethod(#t8) in #t8;
+}
diff --git a/pkg/front_end/testcases/text_serialization.status b/pkg/front_end/testcases/text_serialization.status
@@ -898,6 +898,7 @@ nnbd/issue_39286_2: TextSerializationFailure
 nnbd/late: TextSerializationFailure
 nnbd/null_check: TextSerializationFailure
 nnbd/null_shorting: TextSerializationFailure
+nnbd/null_shorting_cascade: TextSerializationFailure
 nnbd/null_shorting_explicit_extension: TextSerializationFailure
 nnbd/null_shorting_extension: TextSerializationFailure
 nnbd/nullable_null: TextSerializationFailure
