[cfe] Add implicit cast to dynamic guard

Closes #51724

Change-Id: I7db595557693addc31cbda4b70d00e1ba54671b7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/289906
Reviewed-by: Chloe Stefantsova <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>

Author: johnniwinther

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

@@ -171,12 +171,20 @@ class SwitchExpressionResult<Type extends Object, Error>
   /// This is `null` if no such errors where found.
   final Map<int, Error>? nonBooleanGuardErrors;
 
+  /// The types of the guard expressions.
+  ///
+  /// The key is the case index of the guard.
+  ///
+  /// This is `null` if no such guards where present.
+  final Map<int, Type>? guardTypes;
+
   /// Error for when the switch statement was non exhaustive.
   final Error? nonExhaustiveSwitchError;
 
   SwitchExpressionResult(
       {required super.type,
       required this.nonBooleanGuardErrors,
+      required this.guardTypes,
       required this.nonExhaustiveSwitchError});
 }
 
@@ -214,6 +222,13 @@ class SwitchStatementTypeAnalysisResult<Type extends Object, Error> {
   /// This is `null` if no such errors where found.
   final Map<int, Map<int, Error>>? nonBooleanGuardErrors;
 
+  /// The types of the guard expressions.
+  ///
+  /// The keys of the maps are case and head indices of the guard.
+  ///
+  /// This is `null` if no such guards where present.
+  final Map<int, Map<int, Type>>? guardTypes;
+
   /// Error for when the switch statement was non exhaustive.
   final Error? nonExhaustiveSwitchError;
 
@@ -225,6 +240,7 @@ class SwitchStatementTypeAnalysisResult<Type extends Object, Error> {
     required this.scrutineeType,
     required this.switchCaseCompletesNormallyErrors,
     required this.nonBooleanGuardErrors,
+    required this.guardTypes,
     required this.nonExhaustiveSwitchError,
   });
 }
@@ -450,9 +466,13 @@ class IfCaseStatementResult<Type extends Object, Error> {
   /// Error for when the guard has a non-bool type.
   final Error? nonBooleanGuardError;
 
+  /// The type of the guard expression, if present.
+  final Type? guardType;
+
   IfCaseStatementResult(
       {required this.matchedExpressionType,
-      required this.nonBooleanGuardError});
+      required this.nonBooleanGuardError,
+      required this.guardType});
 }
 
 /// Result for analyzing a pattern-for-in statement or element in

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

@@ -623,9 +623,10 @@ mixin TypeAnalyzer<
         variables, componentVariables, patternVariablePromotionKeys,
         location: JoinedPatternVariableLocation.singlePattern);
     Error? nonBooleanGuardError;
+    Type? guardType;
     if (guard != null) {
-      nonBooleanGuardError =
-          _checkGuardType(guard, analyzeExpression(guard, boolType));
+      guardType = analyzeExpression(guard, boolType);
+      nonBooleanGuardError = _checkGuardType(guard, guardType);
     } else {
       handleNoGuard(node, 0);
     }
@@ -634,7 +635,8 @@ mixin TypeAnalyzer<
     _analyzeIfElementCommon(node, ifTrue, ifFalse, context);
     return new IfCaseStatementResult(
         matchedExpressionType: initializerType,
-        nonBooleanGuardError: nonBooleanGuardError);
+        nonBooleanGuardError: nonBooleanGuardError,
+        guardType: guardType);
   }
 
   /// Analyzes a statement of the form `if (expression case pattern) ifTrue` or
@@ -688,9 +690,10 @@ mixin TypeAnalyzer<
     handle_ifCaseStatement_afterPattern(node: node);
     // Stack: (Expression, Pattern)
     Error? nonBooleanGuardError;
+    Type? guardType;
     if (guard != null) {
-      nonBooleanGuardError =
-          _checkGuardType(guard, analyzeExpression(guard, boolType));
+      guardType = analyzeExpression(guard, boolType);
+      nonBooleanGuardError = _checkGuardType(guard, guardType);
     } else {
       handleNoGuard(node, 0);
     }
@@ -699,7 +702,8 @@ mixin TypeAnalyzer<
     _analyzeIfCommon(node, ifTrue, ifFalse);
     return new IfCaseStatementResult(
         matchedExpressionType: initializerType,
-        nonBooleanGuardError: nonBooleanGuardError);
+        nonBooleanGuardError: nonBooleanGuardError,
+        guardType: guardType);
   }
 
   /// Analyzes a collection element of the form `if (condition) ifTrue` or
@@ -1706,6 +1710,7 @@ mixin TypeAnalyzer<
     flow.switchStatement_expressionEnd(null, scrutinee, expressionType);
     Type? lubType;
     Map<int, Error>? nonBooleanGuardErrors;
+    Map<int, Type>? guardTypes;
     for (int i = 0; i < numCases; i++) {
       // Stack: (Expression, i * ExpressionCase)
       SwitchExpressionMemberInfo<Node, Expression, Variable> memberInfo =
@@ -1737,8 +1742,9 @@ mixin TypeAnalyzer<
         guard = memberInfo.head.guard;
         bool hasGuard = guard != null;
         if (hasGuard) {
-          Error? nonBooleanGuardError =
-              _checkGuardType(guard, analyzeExpression(guard, boolType));
+          Type guardType = analyzeExpression(guard, boolType);
+          Error? nonBooleanGuardError = _checkGuardType(guard, guardType);
+          (guardTypes ??= {})[i] = guardType;
           if (nonBooleanGuardError != null) {
             (nonBooleanGuardErrors ??= {})[i] = nonBooleanGuardError;
           }
@@ -1778,6 +1784,7 @@ mixin TypeAnalyzer<
     return new SwitchExpressionResult(
         type: lubType,
         nonBooleanGuardErrors: nonBooleanGuardErrors,
+        guardTypes: guardTypes,
         nonExhaustiveSwitchError: nonExhaustiveSwitchError);
   }
 
@@ -1796,6 +1803,7 @@ mixin TypeAnalyzer<
     bool lastCaseTerminates = true;
     Map<int, Error>? switchCaseCompletesNormallyErrors;
     Map<int, Map<int, Error>>? nonBooleanGuardErrors;
+    Map<int, Map<int, Type>>? guardTypes;
     for (int caseIndex = 0; caseIndex < numCases; caseIndex++) {
       // Stack: (Expression, numExecutionPaths * StatementCase)
       flow.switchStatement_beginAlternatives();
@@ -1835,8 +1843,9 @@ mixin TypeAnalyzer<
           //         numHeads * CaseHead, Pattern),
           guard = head.guard;
           if (guard != null) {
-            Error? nonBooleanGuardError =
-                _checkGuardType(guard, analyzeExpression(guard, boolType));
+            Type guardType = analyzeExpression(guard, boolType);
+            Error? nonBooleanGuardError = _checkGuardType(guard, guardType);
+            ((guardTypes ??= {})[caseIndex] ??= {})[headIndex] = guardType;
             if (nonBooleanGuardError != null) {
               ((nonBooleanGuardErrors ??= {})[caseIndex] ??= {})[headIndex] =
                   nonBooleanGuardError;
@@ -1921,6 +1930,7 @@ mixin TypeAnalyzer<
       scrutineeType: scrutineeType,
       switchCaseCompletesNormallyErrors: switchCaseCompletesNormallyErrors,
       nonBooleanGuardErrors: nonBooleanGuardErrors,
+      guardTypes: guardTypes,
       nonExhaustiveSwitchError: nonExhaustiveSwitchError,
     );
   }

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

@@ -1951,9 +1951,18 @@ class InferenceVisitorImpl extends InferenceVisitorBase
     InvalidExpression? guardError = analysisResult.nonBooleanGuardError;
     if (guardError != null) {
       node.patternGuard.guard = guardError..parent = node.patternGuard;
-    } else if (!identical(node.patternGuard.guard, rewrite)) {
-      node.patternGuard.guard = (rewrite as Expression)
-        ..parent = node.patternGuard;
+    } else {
+      if (!identical(node.patternGuard.guard, rewrite)) {
+        node.patternGuard.guard = (rewrite as Expression)
+          ..parent = node.patternGuard;
+      }
+      if (analysisResult.guardType is DynamicType) {
+        node.patternGuard.guard = _createImplicitAs(
+            node.patternGuard.guard!.fileOffset,
+            node.patternGuard.guard!,
+            coreTypes.boolNonNullableRawType)
+          ..parent = node.patternGuard;
+      }
     }
     rewrite = popRewrite();
     if (!identical(node.patternGuard.pattern, rewrite)) {
@@ -8208,6 +8217,12 @@ class InferenceVisitorImpl extends InferenceVisitorBase
           analysisResult.nonBooleanGuardErrors?[caseIndex];
       if (guardError != null) {
         patternGuard.guard = guardError..parent = patternGuard;
+      } else if (patternGuard.guard != null) {
+        if (analysisResult.guardTypes![caseIndex] is DynamicType) {
+          patternGuard.guard = _createImplicitAs(patternGuard.guard!.fileOffset,
+              patternGuard.guard!, coreTypes.boolNonNullableRawType)
+            ..parent = patternGuard;
+        }
       }
     }
 
@@ -8360,6 +8375,15 @@ class InferenceVisitorImpl extends InferenceVisitorBase
             analysisResult.nonBooleanGuardErrors?[caseIndex]?[headIndex];
         if (guardError != null) {
           patternGuard.guard = guardError..parent = patternGuard;
+        } else if (patternGuard.guard != null) {
+          if (analysisResult.guardTypes![caseIndex]![headIndex]
+              is DynamicType) {
+            patternGuard.guard = _createImplicitAs(
+                patternGuard.guard!.fileOffset,
+                patternGuard.guard!,
+                coreTypes.boolNonNullableRawType)
+              ..parent = patternGuard;
+          }
         }
 
         Map<String, DartType> inferredVariableTypes = {

pkg/front_end/test/spell_checking_list_tests.txt

@@ -82,6 +82,7 @@ blah
 blorp
 bold
 boo
+bools
 bots
 boundaries
 boundarykey

pkg/front_end/testcases/patterns/dynamic_guard.dart

@@ -0,0 +1,22 @@
+// Copyright (c) 2023, 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.
+
+dynamic guard() => true;
+
+main() {
+  var [a] = [5];
+  int b;
+  [b] = [5];
+  if (a case == 5 when guard()) {
+    a = 6;
+  }
+  var c = switch (a) {
+    int d when guard() => d,
+    _ => 0,
+  };
+  switch (b) {
+    case int e when guard():
+      print(a);
+  }
+}

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

@@ -0,0 +1,64 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+static method guard() → dynamic
+  return true;
+static method main() → dynamic {
+  core::int a;
+  {
+    final synthesized dynamic #0#0 = <core::int>[5];
+    if(!(#0#0{core::List<core::int>}.{core::List::length}{core::int} =={core::num::==}{(core::Object) → core::bool} #C1 && (let final dynamic #t1 = a = #0#0{core::List<core::int>}.{core::List::[]}(0){(core::int) → core::int} in true)))
+      throw new _in::ReachabilityError::•();
+  }
+  core::int b;
+  block {
+    final synthesized dynamic #1#0 = <core::int>[5];
+    if(!(#1#0{core::List<core::int>}.{core::List::length}{core::int} =={core::num::==}{(core::Object) → core::bool} #C1 && (let final dynamic #t2 = b = #1#0{core::List<core::int>}.{core::List::[]}(0){(core::int) → core::int} in true)))
+      throw new _in::ReachabilityError::•();
+  } =>#1#0;
+  {
+    final synthesized core::int #2#0 = a;
+    if(#2#0 =={core::num::==}{(core::Object) → core::bool} #C2 && self::guard() as{TypeError,ForNonNullableByDefault} core::bool) {
+      a = 6;
+    }
+  }
+  core::int c = block {
+    core::int #t3;
+    final synthesized core::int #3#0 = a;
+    #L1:
+    {
+      {
+        core::int d;
+        if(#3#0 is{ForNonNullableByDefault} core::int && (let final dynamic #t4 = d = #3#0 in true) && self::guard() as{TypeError,ForNonNullableByDefault} core::bool) {
+          #t3 = d;
+          break #L1;
+        }
+      }
+      {
+        if(true) {
+          #t3 = 0;
+          break #L1;
+        }
+      }
+    }
+  } =>#t3;
+  #L2:
+  {
+    final synthesized core::int #4#0 = b;
+    {
+      core::int e;
+      if(#4#0 is{ForNonNullableByDefault} core::int && (let final dynamic #t5 = e = #4#0 in true) && self::guard() as{TypeError,ForNonNullableByDefault} core::bool) {
+        {
+          core::print(a);
+        }
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 1
+  #C2 = 5
+}

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

@@ -0,0 +1,64 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+import "dart:_internal" as _in;
+
+static method guard() → dynamic
+  return true;
+static method main() → dynamic {
+  core::int a;
+  {
+    final synthesized dynamic #0#0 = core::_GrowableList::_literal1<core::int>(5);
+    if(!(#0#0{core::List<core::int>}.{core::List::length}{core::int} =={core::num::==}{(core::Object) → core::bool} #C1 && (let final core::int #t1 = a = #0#0{core::List<core::int>}.{core::List::[]}(0){(core::int) → core::int} in true)))
+      throw new _in::ReachabilityError::•();
+  }
+  core::int b;
+  block {
+    final synthesized dynamic #1#0 = core::_GrowableList::_literal1<core::int>(5);
+    if(!(#1#0{core::List<core::int>}.{core::List::length}{core::int} =={core::num::==}{(core::Object) → core::bool} #C1 && (let final core::int #t2 = b = #1#0{core::List<core::int>}.{core::List::[]}(0){(core::int) → core::int} in true)))
+      throw new _in::ReachabilityError::•();
+  } =>#1#0;
+  {
+    final synthesized core::int #2#0 = a;
+    if(#2#0 =={core::num::==}{(core::Object) → core::bool} #C2 && self::guard() as{TypeError,ForNonNullableByDefault} core::bool) {
+      a = 6;
+    }
+  }
+  core::int c = block {
+    core::int #t3;
+    final synthesized core::int #3#0 = a;
+    #L1:
+    {
+      {
+        core::int d;
+        if(#3#0 is{ForNonNullableByDefault} core::int && (let final core::int #t4 = d = #3#0 in true) && self::guard() as{TypeError,ForNonNullableByDefault} core::bool) {
+          #t3 = d;
+          break #L1;
+        }
+      }
+      {
+        if(true) {
+          #t3 = 0;
+          break #L1;
+        }
+      }
+    }
+  } =>#t3;
+  #L2:
+  {
+    final synthesized core::int #4#0 = b;
+    {
+      core::int e;
+      if(#4#0 is{ForNonNullableByDefault} core::int && (let final core::int #t5 = e = #4#0 in true) && self::guard() as{TypeError,ForNonNullableByDefault} core::bool) {
+        {
+          core::print(a);
+        }
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 1
+  #C2 = 5
+}

pkg/front_end/testcases/patterns/dynamic_guard.dart.textual_outline.expect

@@ -0,0 +1,2 @@
+dynamic guard() => true;
+main() {}

pkg/front_end/testcases/patterns/dynamic_guard.dart.textual_outline_modelled.expect

@@ -0,0 +1,2 @@
+dynamic guard() => true;
+main() {}