[cfe] Avoid repearing type inference on pattern for-in loops

Previously the type inference was repeated in order to obtain the
static type of the iterable expression. That type is computed in the
shared analysis, and this CL passes the computed type to the clients
of the analysis routine in the result object.

In addition to being redundant, the repeated inference pass caused
crashes.

Closes #53092

Change-Id: I63d3d82be046884fa16d904a43e3bb6e01cf6f7e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/321141
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Chloe Stefantsova <[email protected]>

Author: chloestefantsova

pkg/_fe_analyzer_shared/lib/src/type_inference/type_analysis_result.dart

@@ -320,11 +320,15 @@ class PatternForInResult<Type extends Object, Error> {
   /// The static type of the elements of the for in expression.
   final Type elementType;
 
+  /// The static type of the collection of elements of the for in expression.
+  final Type expressionType;
+
   /// Error for when the expression is not an iterable.
   final Error? patternForInExpressionIsNotIterableError;
 
   PatternForInResult(
       {required this.elementType,
+      required this.expressionType,
       required this.patternForInExpressionIsNotIterableError});
 }
 

pkg/_fe_analyzer_shared/lib/src/type_inference/type_analyzer.dart

@@ -1425,6 +1425,7 @@ mixin TypeAnalyzer<
 
     return new PatternForInResult(
         elementType: elementType,
+        expressionType: expressionType,
         patternForInExpressionIsNotIterableError:
             patternForInExpressionIsNotIterableError);
   }

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

@@ -1636,20 +1636,28 @@ class InferenceVisitorImpl extends InferenceVisitorBase
     ForInVariable forInVariable =
         new PatternVariableDeclarationForInVariable(patternVariableDeclaration);
 
-    DartType elementType = forInVariable.computeElementType(this);
-    ExpressionInferenceResult iterableResult =
-        inferForInIterable(iterable, elementType, isAsync: isAsync);
-    DartType inferredType = iterableResult.inferredType;
-    variable.type = inferredType;
+    variable.type = result.elementType;
+    iterable = ensureAssignable(
+        wrapType(
+            const DynamicType(),
+            isAsync ? coreTypes.streamClass : coreTypes.iterableClass,
+            libraryBuilder.nonNullable),
+        result.expressionType,
+        iterable,
+        errorTemplate: templateForInLoopTypeNotIterable,
+        nullabilityErrorTemplate: templateForInLoopTypeNotIterableNullability,
+        nullabilityPartErrorTemplate:
+            templateForInLoopTypeNotIterablePartNullability);
     // This is matched by the call to [forEach_end] in
     // [inferElement], [inferMapEntry] or [inferForInStatement].
     flowAnalysis.forEach_bodyBegin(node);
-    syntheticAssignment = forInVariable.inferAssignment(this, inferredType);
+    syntheticAssignment =
+        forInVariable.inferAssignment(this, result.elementType);
     if (syntheticAssignment is VariableSet) {
-      flowAnalysis.write(node, variable, inferredType, null);
+      flowAnalysis.write(node, variable, result.elementType, null);
     }
 
-    return new ForInResult(variable, iterableResult.expression,
+    return new ForInResult(variable, /*iterableResult.expression*/ iterable,
         syntheticAssignment, patternVariableDeclaration);
   }
 

pkg/front_end/testcases/patterns/for_in_inference_error.dart.strong.expect

@@ -11,7 +11,7 @@ import self as self;
 import "dart:core" as core;
 
 static method test() → dynamic {
-  for (final dynamic #t1 in invalid-expression "pkg/front_end/testcases/patterns/for_in_inference_error.dart:6:23: Error: The type 'int' used in the 'for' loop must implement 'Iterable<dynamic>'.
+  for (final invalid-type #t1 in invalid-expression "pkg/front_end/testcases/patterns/for_in_inference_error.dart:6:23: Error: The type 'int' used in the 'for' loop must implement 'Iterable<dynamic>'.
  - 'Iterable' is from 'dart:core'.
   for (var [int x] in 0) {} // Error.
                       ^" in 0 as{TypeError} core::Iterable<dynamic>) {

pkg/front_end/testcases/patterns/for_in_inference_error.dart.strong.transformed.expect

@@ -17,7 +17,7 @@ static method test() → dynamic {
   for (var [int x] in 0) {} // Error.
                       ^" in 0 as{TypeError} core::Iterable<dynamic>.{core::Iterable::iterator}{core::Iterator<Never>};
     for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
-      final dynamic #t1 = :sync-for-iterator.{core::Iterator::current}{Never};
+      final invalid-type #t1 = :sync-for-iterator.{core::Iterator::current}{Never};
       {
         hoisted core::int x;
         {

pkg/front_end/testcases/patterns/for_in_inference_error.dart.weak.expect

@@ -11,7 +11,7 @@ import self as self;
 import "dart:core" as core;
 
 static method test() → dynamic {
-  for (final dynamic #t1 in invalid-expression "pkg/front_end/testcases/patterns/for_in_inference_error.dart:6:23: Error: The type 'int' used in the 'for' loop must implement 'Iterable<dynamic>'.
+  for (final invalid-type #t1 in invalid-expression "pkg/front_end/testcases/patterns/for_in_inference_error.dart:6:23: Error: The type 'int' used in the 'for' loop must implement 'Iterable<dynamic>'.
  - 'Iterable' is from 'dart:core'.
   for (var [int x] in 0) {} // Error.
                       ^" in 0 as{TypeError} core::Iterable<dynamic>) {

pkg/front_end/testcases/patterns/for_in_inference_error.dart.weak.modular.expect

@@ -11,7 +11,7 @@ import self as self;
 import "dart:core" as core;
 
 static method test() → dynamic {
-  for (final dynamic #t1 in invalid-expression "pkg/front_end/testcases/patterns/for_in_inference_error.dart:6:23: Error: The type 'int' used in the 'for' loop must implement 'Iterable<dynamic>'.
+  for (final invalid-type #t1 in invalid-expression "pkg/front_end/testcases/patterns/for_in_inference_error.dart:6:23: Error: The type 'int' used in the 'for' loop must implement 'Iterable<dynamic>'.
  - 'Iterable' is from 'dart:core'.
   for (var [int x] in 0) {} // Error.
                       ^" in 0 as{TypeError} core::Iterable<dynamic>) {

pkg/front_end/testcases/patterns/for_in_inference_error.dart.weak.transformed.expect

@@ -17,7 +17,7 @@ static method test() → dynamic {
   for (var [int x] in 0) {} // Error.
                       ^" in 0 as{TypeError} core::Iterable<dynamic>.{core::Iterable::iterator}{core::Iterator<Never>};
     for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
-      final dynamic #t1 = :sync-for-iterator.{core::Iterator::current}{Never};
+      final invalid-type #t1 = :sync-for-iterator.{core::Iterator::current}{Never};
       {
         hoisted core::int x;
         {

pkg/front_end/testcases/patterns/issue52228.dart.strong.expect

@@ -8,11 +8,11 @@ library;
 //   ^^^^^
 //
 import self as self;
-import "dart:async" as asy;
 import "dart:core" as core;
+import "dart:async" as asy;
 
 static method test() → dynamic {
-  await for (final dynamic #t1 in asy::Stream::fromIterable<dynamic>(<core::List<core::int>>[<core::int>[1], <core::int>[2], <core::int>[3]])) {
+  await for (final core::List<core::int> #t1 in asy::Stream::fromIterable<core::List<core::int>>(<core::List<core::int>>[<core::int>[1], <core::int>[2], <core::int>[3]])) {
     hoisted core::int v1;
     {
       final synthesized core::List<core::int> #0#0 = #t1;

pkg/front_end/testcases/patterns/issue52228.dart.strong.transformed.expect

@@ -8,11 +8,11 @@ library;
 //   ^^^^^
 //
 import self as self;
-import "dart:async" as asy;
 import "dart:core" as core;
+import "dart:async" as asy;
 
 static method test() → dynamic {
-  await for (final dynamic #t1 in asy::Stream::fromIterable<dynamic>(core::_GrowableList::_literal3<core::List<core::int>>(core::_GrowableList::_literal1<core::int>(1), core::_GrowableList::_literal1<core::int>(2), core::_GrowableList::_literal1<core::int>(3)))) {
+  await for (final core::List<core::int> #t1 in asy::Stream::fromIterable<core::List<core::int>>(core::_GrowableList::_literal3<core::List<core::int>>(core::_GrowableList::_literal1<core::int>(1), core::_GrowableList::_literal1<core::int>(2), core::_GrowableList::_literal1<core::int>(3)))) {
     hoisted core::int v1;
     {
       final synthesized core::List<core::int> #0#0 = #t1;

pkg/front_end/testcases/patterns/issue52228.dart.weak.expect

@@ -8,11 +8,11 @@ library;
 //   ^^^^^
 //
 import self as self;
-import "dart:async" as asy;
 import "dart:core" as core;
+import "dart:async" as asy;
 
 static method test() → dynamic {
-  await for (final dynamic #t1 in asy::Stream::fromIterable<dynamic>(<core::List<core::int>>[<core::int>[1], <core::int>[2], <core::int>[3]])) {
+  await for (final core::List<core::int> #t1 in asy::Stream::fromIterable<core::List<core::int>>(<core::List<core::int>>[<core::int>[1], <core::int>[2], <core::int>[3]])) {
     hoisted core::int v1;
     {
       final synthesized core::List<core::int> #0#0 = #t1;

pkg/front_end/testcases/patterns/issue52228.dart.weak.modular.expect

@@ -8,11 +8,11 @@ library;
 //   ^^^^^
 //
 import self as self;
-import "dart:async" as asy;
 import "dart:core" as core;
+import "dart:async" as asy;
 
 static method test() → dynamic {
-  await for (final dynamic #t1 in asy::Stream::fromIterable<dynamic>(<core::List<core::int>>[<core::int>[1], <core::int>[2], <core::int>[3]])) {
+  await for (final core::List<core::int> #t1 in asy::Stream::fromIterable<core::List<core::int>>(<core::List<core::int>>[<core::int>[1], <core::int>[2], <core::int>[3]])) {
     hoisted core::int v1;
     {
       final synthesized core::List<core::int> #0#0 = #t1;

pkg/front_end/testcases/patterns/issue52228.dart.weak.transformed.expect

@@ -8,11 +8,11 @@ library;
 //   ^^^^^
 //
 import self as self;
-import "dart:async" as asy;
 import "dart:core" as core;
+import "dart:async" as asy;
 
 static method test() → dynamic {
-  await for (final dynamic #t1 in asy::Stream::fromIterable<dynamic>(core::_GrowableList::_literal3<core::List<core::int>>(core::_GrowableList::_literal1<core::int>(1), core::_GrowableList::_literal1<core::int>(2), core::_GrowableList::_literal1<core::int>(3)))) {
+  await for (final core::List<core::int> #t1 in asy::Stream::fromIterable<core::List<core::int>>(core::_GrowableList::_literal3<core::List<core::int>>(core::_GrowableList::_literal1<core::int>(1), core::_GrowableList::_literal1<core::int>(2), core::_GrowableList::_literal1<core::int>(3)))) {
     hoisted core::int v1;
     {
       final synthesized core::List<core::int> #0#0 = #t1;