[cfe] Account for non-pattern case heads when joining variables

Part of #49749

Change-Id: Ib7530e476c09402405d2763f1f7c29b2f29c3bdb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/286461
Reviewed-by: Johnni Winther <[email protected]>
Commit-Queue: Chloe Stefantsova <[email protected]>

Author: chloestefantsova

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

@@ -7830,6 +7830,10 @@ class BodyBuilder extends StackListenerImpl
             }
             jointPatternVariables = sharedVariables;
           }
+        } else {
+          // It's a non-pattern head, so no variables can be joined.
+          jointPatternVariables = null;
+          break;
         }
       }
       if (jointPatternVariables != null) {

pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart

@@ -0,0 +1,14 @@
+// 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.
+
+test(dynamic x) {
+  switch (x) {
+    case final a when a > 0:
+    case 0:
+    case final a:
+      return a; // Error.
+    default:
+      return null;
+  }
+}

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

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+//       return a; // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → dynamic {
+  #L1:
+  {
+    final dynamic a;
+    final dynamic a#1;
+    final dynamic #0#0 = x;
+    if((let final dynamic #t1 = a = #0#0 in true) && a{dynamic}.>(0) || #C1 =={core::num::==}{(core::Object) → core::bool} #0#0 || (let final dynamic #t2 = a#1 = #0#0 in true)) {
+      {
+        return invalid-expression "pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+      return a; // Error.
+             ^";
+      }
+    }
+    else {
+      {
+        return null;
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 0
+}

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

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+//       return a; // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → dynamic {
+  #L1:
+  {
+    final dynamic a;
+    final dynamic a#1;
+    final dynamic #0#0 = x;
+    if((let final dynamic #t1 = a = #0#0 in true) && a{dynamic}.>(0) || #C1 =={core::num::==}{(core::Object) → core::bool} #0#0 || (let final dynamic #t2 = a#1 = #0#0 in true)) {
+      {
+        return invalid-expression "pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+      return a; // Error.
+             ^";
+      }
+    }
+    else {
+      {
+        return null;
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 0
+}

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

@@ -0,0 +1 @@
+test(dynamic x) {}

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

@@ -0,0 +1 @@
+test(dynamic x) {}

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

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+//       return a; // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → dynamic {
+  #L1:
+  {
+    final dynamic a;
+    final dynamic a#1;
+    final dynamic #0#0 = x;
+    if((let final dynamic #t1 = a = #0#0 in true) && a{dynamic}.>(0) || #C1 =={core::num::==}{(core::Object) → core::bool} #0#0 || (let final dynamic #t2 = a#1 = #0#0 in true)) {
+      {
+        return invalid-expression "pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+      return a; // Error.
+             ^";
+      }
+    }
+    else {
+      {
+        return null;
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 0
+}

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

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+//       return a; // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → dynamic {
+  #L1:
+  {
+    final dynamic a;
+    final dynamic a#1;
+    final dynamic #0#0 = x;
+    if((let final dynamic #t1 = a = #0#0 in true) && a{dynamic}.>(0) || #C1 =={core::num::==}{(core::Object) → core::bool} #0#0 || (let final dynamic #t2 = a#1 = #0#0 in true)) {
+      {
+        return invalid-expression "pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+      return a; // Error.
+             ^";
+      }
+    }
+    else {
+      {
+        return null;
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 0
+}

pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart.weak.outline.expect

@@ -0,0 +1,5 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+
+static method test(dynamic x) → dynamic
+  ;

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

@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+//       return a; // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+static method test(dynamic x) → dynamic {
+  #L1:
+  {
+    final dynamic a;
+    final dynamic a#1;
+    final dynamic #0#0 = x;
+    if((let final dynamic #t1 = a = #0#0 in true) && a{dynamic}.>(0) || #C1 =={core::num::==}{(core::Object) → core::bool} #0#0 || (let final dynamic #t2 = a#1 = #0#0 in true)) {
+      {
+        return invalid-expression "pkg/front_end/testcases/patterns/non_pattern_case_among_pattern_cases_in_switch.dart:10:14: Error: Undefined name 'a'.
+      return a; // Error.
+             ^";
+      }
+    }
+    else {
+      {
+        return null;
+      }
+    }
+  }
+}
+
+constants  {
+  #C1 = 0
+}