Fix "why not promoted" functionality for compound indexed assignment.

Bug: #44898
Change-Id: I40c6087a0db2c67106f9ce138b79a8a5769b37de
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/193834
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: stereotype441

pkg/_fe_analyzer_shared/test/flow_analysis/why_not_promoted/data/argument_type_not_assignable_nullability_error.dart

@@ -429,51 +429,47 @@ class C29 {
 }
 
 indexSetCompound(C29 c, List<int> values) {
-  // TODO(paulberry): get this to work with the CFE
   if (c.bad == null) return;
   values[
       /*analyzer.notPromoted(propertyNotPromoted(target: member:C29.bad, type: int?))*/ c
-          .bad] += 1;
+          . /*cfe.notPromoted(propertyNotPromoted(target: member:C29.bad, type: int?))*/ bad] += 1;
 }
 
 class C30 {
   int? bad;
 }
 
 indexSetIfNull(C30 c, List<int?> values) {
-  // TODO(paulberry): get this to work with the CFE
   if (c.bad == null) return;
   values[
       /*analyzer.notPromoted(propertyNotPromoted(target: member:C30.bad, type: int?))*/ c
-          .bad] ??= 1;
+          . /*cfe.notPromoted(propertyNotPromoted(target: member:C30.bad, type: int?))*/ bad] ??= 1;
 }
 
 class C31 {
   int? bad;
 }
 
 indexSetPreIncDec(C31 c, List<int> values) {
-  // TODO(paulberry): get this to work with the CFE
   if (c.bad == null) return;
   ++values[
       /*analyzer.notPromoted(propertyNotPromoted(target: member:C31.bad, type: int?))*/ c
-          .bad];
+          . /*cfe.notPromoted(propertyNotPromoted(target: member:C31.bad, type: int?))*/ bad];
   --values[
       /*analyzer.notPromoted(propertyNotPromoted(target: member:C31.bad, type: int?))*/ c
-          .bad];
+          . /*cfe.notPromoted(propertyNotPromoted(target: member:C31.bad, type: int?))*/ bad];
 }
 
 class C32 {
   int? bad;
 }
 
 indexSetPostIncDec(C32 c, List<int> values) {
-  // TODO(paulberry): get this to work with the CFE
   if (c.bad == null) return;
   values[
       /*analyzer.notPromoted(propertyNotPromoted(target: member:C32.bad, type: int?))*/ c
-          .bad]++;
+          . /*cfe.notPromoted(propertyNotPromoted(target: member:C32.bad, type: int?))*/ bad]++;
   values[
       /*analyzer.notPromoted(propertyNotPromoted(target: member:C32.bad, type: int?))*/ c
-          .bad]--;
+          . /*cfe.notPromoted(propertyNotPromoted(target: member:C32.bad, type: int?))*/ bad]--;
 }

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

@@ -4,6 +4,7 @@
 
 // @dart = 2.9
 
+import 'package:_fe_analyzer_shared/src/flow_analysis/flow_analysis.dart';
 import 'package:_fe_analyzer_shared/src/util/link.dart';
 import 'package:front_end/src/api_prototype/lowering_predicates.dart';
 import 'package:kernel/ast.dart';
@@ -3372,6 +3373,8 @@ class InferenceVisitor
 
     VariableDeclaration indexVariable;
     Expression readIndex = indexResult.expression;
+    Map<DartType, NonPromotionReason> Function() whyNotPromotedIndex =
+        inferrer.flowAnalysis?.whyNotPromoted(readIndex);
     Expression writeIndex;
     if (isPureExpression(readIndex)) {
       writeIndex = clonePureExpression(readIndex);
@@ -3382,7 +3385,8 @@ class InferenceVisitor
     }
 
     readIndex = inferrer.ensureAssignable(
-        readIndexType, indexResult.inferredType, readIndex);
+        readIndexType, indexResult.inferredType, readIndex,
+        whyNotPromoted: whyNotPromotedIndex);
 
     ExpressionInferenceResult readResult = _computeIndexGet(
         node.readOffset,
@@ -3403,7 +3407,8 @@ class InferenceVisitor
         .member;
 
     writeIndex = inferrer.ensureAssignable(
-        writeIndexType, indexResult.inferredType, writeIndex);
+        writeIndexType, indexResult.inferredType, writeIndex,
+        whyNotPromoted: whyNotPromotedIndex);
 
     ExpressionInferenceResult valueResult = inferrer
         .inferExpression(node.value, valueType, true, isVoidAllowed: true);
@@ -5055,6 +5060,8 @@ class InferenceVisitor
 
     VariableDeclaration indexVariable;
     Expression readIndex = indexResult.expression;
+    Map<DartType, NonPromotionReason> Function() whyNotPromotedIndex =
+        inferrer.flowAnalysis?.whyNotPromoted(readIndex);
     Expression writeIndex;
     if (isPureExpression(readIndex)) {
       writeIndex = clonePureExpression(readIndex);
@@ -5065,7 +5072,8 @@ class InferenceVisitor
     }
 
     readIndex = inferrer.ensureAssignable(
-        readIndexType, indexResult.inferredType, readIndex);
+        readIndexType, indexResult.inferredType, readIndex,
+        whyNotPromoted: whyNotPromotedIndex);
 
     ExpressionInferenceResult readResult = _computeIndexGet(
         node.readOffset,
@@ -5110,7 +5118,8 @@ class InferenceVisitor
     DartType binaryType = binaryResult.inferredType;
 
     writeIndex = inferrer.ensureAssignable(
-        writeIndexType, indexResult.inferredType, writeIndex);
+        writeIndexType, indexResult.inferredType, writeIndex,
+        whyNotPromoted: whyNotPromotedIndex);
 
     binary = inferrer.ensureAssignable(valueType, binaryType, binary,
         fileOffset: node.fileOffset);

pkg/front_end/lib/src/fasta/type_inference/type_inferrer.dart

@@ -316,7 +316,17 @@ class TypeInferrerImpl implements TypeInferrer {
           if (args.isNotEmpty) {
             nonPromotionReasonText += '(${args.join(', ')})';
           }
-          dataForTesting.flowAnalysisResult.nonPromotionReasons[node] =
+          TreeNode origNode = node;
+          while (origNode is VariableGet &&
+              origNode.variable.name == null &&
+              origNode.variable.initializer != null) {
+            // This is a read of a synthetic variable, presumably from a "let".
+            // Find the original expression.
+            // TODO(johnniwinther): add a general solution for getting the
+            // original node for testing.
+            origNode = (origNode as VariableGet).variable.initializer;
+          }
+          dataForTesting.flowAnalysisResult.nonPromotionReasons[origNode] =
               nonPromotionReasonText;
         }
         // Note: this will always pick the first viable reason (only).  I
@@ -478,7 +488,8 @@ class TypeInferrerImpl implements TypeInferrer {
       Template<Message Function(DartType, DartType, bool)>
           nullabilityNullTypeErrorTemplate,
       Template<Message Function(DartType, DartType, DartType, DartType, bool)>
-          nullabilityPartErrorTemplate}) {
+          nullabilityPartErrorTemplate,
+      Map<DartType, NonPromotionReason> Function() whyNotPromoted}) {
     assert(contextType != null);
 
     // [errorTemplate], [nullabilityErrorTemplate], and
@@ -607,14 +618,15 @@ class TypeInferrerImpl implements TypeInferrer {
                     declaredContextType ?? contextType,
                     isNonNullableByDefault));
           } else {
+            whyNotPromoted ??= flowAnalysis?.whyNotPromoted(expression);
             result = _wrapUnassignableExpression(
                 expression,
                 expressionType,
                 contextType,
                 nullabilityErrorTemplate.withArguments(expressionType,
                     declaredContextType ?? contextType, isNonNullableByDefault),
                 context: getWhyNotPromotedContext(
-                    flowAnalysis?.whyNotPromoted(expression)(),
+                    whyNotPromoted?.call(),
                     expression,
                     (type) => typeSchemaEnvironment.isSubtypeOf(type,
                         contextType, SubtypeCheckMode.withNullabilities)));

pkg/front_end/test/spell_checking_list_code.txt

@@ -809,6 +809,7 @@ ordered
 orders
 ordinal
 org
+orig
 orphancy
 orphans
 ors
@@ -884,6 +885,7 @@ preexisting
 preorder
 presented
 presubmit
+presumably
 prev
 prime
 printer