Recognize synthetic catch-clause and unhandled exceptions.

Bug: flutter/flutter#16741
Change-Id: I619c2eb0662cfdd16cc865ae5eae9c7d19bc55c4
Reviewed-on: https://dart-review.googlesource.com/52984
Commit-Queue: Alexander Aprelev <[email protected]>
Reviewed-by: Alexander Markov <[email protected]>
Reviewed-by: Jens Johansen <[email protected]>

Author: aam

pkg/kernel/binary.md

@@ -1050,8 +1050,8 @@ type ReturnStatement extends Statement {
 type TryCatch extends Statement {
   Byte tag = 75;
   Statement body;
-  // 1 if any catch needs a stacktrace (have a stacktrace variable).
-  Byte anyCatchNeedsStackTrace;
+  // "any catch needs a stacktrace" means it has a stacktrace variable.
+  Byte flags (anyCatchNeedsStackTrace, isSynthesized);
   List<Catch> catches;
 }
 

pkg/kernel/lib/ast.dart

@@ -4174,8 +4174,9 @@ class ReturnStatement extends Statement {
 class TryCatch extends Statement {
   Statement body;
   List<Catch> catches;
+  bool isSynthetic;
 
-  TryCatch(this.body, this.catches) {
+  TryCatch(this.body, this.catches, {this.isSynthetic: false}) {
     body?.parent = this;
     setParents(catches, this);
   }

pkg/kernel/lib/binary/ast_from_binary.dart

@@ -1549,8 +1549,8 @@ class BinaryBuilder {
         return new ReturnStatement(readExpressionOption())..fileOffset = offset;
       case Tag.TryCatch:
         Statement body = readStatement();
-        readByte(); // whether any catch needs a stacktrace.
-        return new TryCatch(body, readCatchList());
+        int flags = readByte();
+        return new TryCatch(body, readCatchList(), isSynthetic: flags & 2 == 2);
       case Tag.TryFinally:
         return new TryFinally(readStatement(), readStatement());
       case Tag.YieldStatement:

pkg/kernel/lib/binary/ast_to_binary.dart

@@ -1544,17 +1544,16 @@ class BinaryPrinter implements Visitor<void>, BinarySink {
     writeOptionalNode(node.expression);
   }
 
+  int _encodeTryCatchFlags(bool needsStackTrace, bool isSynthetic) {
+    return (needsStackTrace ? 1 : 0) | (isSynthetic ? 2 : 0);
+  }
+
   @override
   void visitTryCatch(TryCatch node) {
     writeByte(Tag.TryCatch);
     writeNode(node.body);
-    if (node.catches.any((Catch c) => c.stackTrace != null)) {
-      // at least one catch needs the stack trace.
-      writeByte(1);
-    } else {
-      // no catch needs the stack trace.
-      writeByte(0);
-    }
+    bool needsStackTrace = node.catches.any((Catch c) => c.stackTrace != null);
+    writeByte(_encodeTryCatchFlags(needsStackTrace, node.isSynthetic));
     writeNodeList(node.catches);
   }
 

pkg/kernel/lib/binary/tag.dart

@@ -135,7 +135,7 @@ class Tag {
   /// Internal version of kernel binary format.
   /// Bump it when making incompatible changes in kernel binaries.
   /// Keep in sync with runtime/vm/kernel_binary.h.
-  static const int BinaryFormatVersion = 4;
+  static const int BinaryFormatVersion = 5;
 }
 
 abstract class ConstantTag {

pkg/kernel/lib/clone.dart

@@ -372,7 +372,8 @@ class CloneVisitor implements TreeVisitor {
   }
 
   visitTryCatch(TryCatch node) {
-    return new TryCatch(clone(node.body), node.catches.map(clone).toList());
+    return new TryCatch(clone(node.body), node.catches.map(clone).toList(),
+        isSynthetic: node.isSynthetic);
   }
 
   visitCatch(Catch node) {

pkg/kernel/lib/transformations/continuation.dart

@@ -355,14 +355,18 @@ abstract class AsyncRewriterBase extends ContinuationRewriterBase {
     var exceptionVariable = new VariableDeclaration(":exception");
     var stackTraceVariable = new VariableDeclaration(":stack_trace");
 
-    return new TryCatch(buildReturn(labeledBody), <Catch>[
-      new Catch(
-          exceptionVariable,
-          new Block(<Statement>[
-            buildCatchBody(exceptionVariable, stackTraceVariable)
-          ]),
-          stackTrace: stackTraceVariable)
-    ]);
+    return new TryCatch(
+      buildReturn(labeledBody),
+      <Catch>[
+        new Catch(
+            exceptionVariable,
+            new Block(<Statement>[
+              buildCatchBody(exceptionVariable, stackTraceVariable)
+            ]),
+            stackTrace: stackTraceVariable)
+      ],
+      isSynthetic: true,
+    );
   }
 
   Statement buildCatchBody(

runtime/observatory/tests/service/service_kernel.status

@@ -16,7 +16,6 @@ evaluate_activation_in_method_class_test: RuntimeError
 evaluate_activation_test/instance: RuntimeError
 evaluate_activation_test/scope: RuntimeError
 evaluate_in_sync_star_activation_test: RuntimeError
-pause_on_unhandled_async_exceptions2_test: RuntimeError # --pause-isolates-on-unhandled-exceptions doesn't currently work. Issue #29056
 pause_on_unhandled_async_exceptions_test: RuntimeError #  --pause-isolates-on-unhandled-exceptions doesn't currently work. Issue #29056
 step_through_arithmetic_test: RuntimeError # probably constant evaluator pre-evaluating e.g. 1+2
 unused_changes_in_last_reload_test: RuntimeError

runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc

@@ -1807,7 +1807,7 @@ void StreamingScopeBuilder::VisitStatement() {
       ++depth_.catch_;
       AddCatchVariables();
 
-      builder_->ReadBool();  // read any_catch_needs_stack_trace.
+      builder_->ReadByte();  // read flags
       intptr_t catch_count =
           builder_->ReadListLength();  // read number of catches.
       for (intptr_t i = 0; i < catch_count; ++i) {
@@ -4355,7 +4355,7 @@ void KernelFingerprintHelper::CalculateStatementFingerprint() {
     }
     case kTryCatch: {
       CalculateStatementFingerprint();  // read body.
-      BuildHash(ReadBool());            // read any_catch_needs_stack_trace.
+      BuildHash(ReadByte());            // read flags
       intptr_t catch_count = ReadListLength();  // read number of catches.
       for (intptr_t i = 0; i < catch_count; ++i) {
         ReadPosition();                  // read position.
@@ -6603,7 +6603,7 @@ void KernelReaderHelper::SkipStatement() {
     }
     case kTryCatch: {
       SkipStatement();  // read body.
-      ReadBool();       // read any_catch_needs_stack_trace.
+      ReadByte();       // read flags
       intptr_t catch_count = ReadListLength();  // read number of catches.
       for (intptr_t i = 0; i < catch_count; ++i) {
         ReadPosition();   // read position.
@@ -7163,9 +7163,10 @@ Fragment StreamingFlowGraphBuilder::BranchIfNull(
 
 Fragment StreamingFlowGraphBuilder::CatchBlockEntry(const Array& handler_types,
                                                     intptr_t handler_index,
-                                                    bool needs_stacktrace) {
+                                                    bool needs_stacktrace,
+                                                    bool is_synthesized) {
   return flow_graph_builder_->CatchBlockEntry(handler_types, handler_index,
-                                              needs_stacktrace);
+                                              needs_stacktrace, is_synthesized);
 }
 
 Fragment StreamingFlowGraphBuilder::TryCatch(int try_handler_index) {
@@ -9851,14 +9852,21 @@ Fragment StreamingFlowGraphBuilder::BuildTryCatch() {
   }
   try_depth_dec();
 
-  bool needs_stacktrace = ReadBool();  // read any_catch_needs_stack_trace
+  const int kNeedsStracktraceBit = 1 << 0;
+  const int kIsSyntheticBit = 1 << 1;
+
+  uint8_t flags = ReadByte();
+  bool needs_stacktrace =
+      (flags & kNeedsStracktraceBit) == kNeedsStracktraceBit;
+  bool is_synthetic = (flags & kIsSyntheticBit) == kIsSyntheticBit;
 
   catch_depth_inc();
   intptr_t catch_count = ReadListLength();  // read number of catches.
   const Array& handler_types =
       Array::ZoneHandle(Z, Array::New(catch_count, Heap::kOld));
-  Fragment catch_body =
-      CatchBlockEntry(handler_types, try_handler_index, needs_stacktrace);
+
+  Fragment catch_body = CatchBlockEntry(handler_types, try_handler_index,
+                                        needs_stacktrace, is_synthetic);
   // Fill in the body of the catch.
   for (intptr_t i = 0; i < catch_count; ++i) {
     intptr_t catch_offset = ReaderOffset();   // Catch has no tag.
@@ -10029,7 +10037,8 @@ Fragment StreamingFlowGraphBuilder::BuildTryFinally() {
   handler_types.SetAt(0, Object::dynamic_type());
   // Note: rethrow will actually force mark the handler as needing a stacktrace.
   Fragment finally_body = CatchBlockEntry(handler_types, try_handler_index,
-                                          /* needs_stacktrace = */ false);
+                                          /* needs_stacktrace = */ false,
+                                          /* is_synthesized = */ true);
   SetOffset(finalizer_offset);
   finally_body += BuildStatement();  // read finalizer
   if (finally_body.is_open()) {

runtime/vm/compiler/frontend/kernel_binary_flowgraph.h

@@ -1421,7 +1421,8 @@ class StreamingFlowGraphBuilder : public KernelReaderHelper {
                         bool negate = false);
   Fragment CatchBlockEntry(const Array& handler_types,
                            intptr_t handler_index,
-                           bool needs_stacktrace);
+                           bool needs_stacktrace,
+                           bool is_synthesized);
   Fragment TryCatch(int try_handler_index);
   Fragment Drop();
 

runtime/vm/compiler/frontend/kernel_to_il.cc

@@ -1176,14 +1176,15 @@ Fragment BaseFlowGraphBuilder::BranchIfStrictEqual(
 
 Fragment FlowGraphBuilder::CatchBlockEntry(const Array& handler_types,
                                            intptr_t handler_index,
-                                           bool needs_stacktrace) {
+                                           bool needs_stacktrace,
+                                           bool is_synthesized) {
   ASSERT(CurrentException()->is_captured() ==
          CurrentStackTrace()->is_captured());
   const bool should_restore_closure_context =
       CurrentException()->is_captured() || CurrentCatchContext()->is_captured();
   CatchBlockEntryInstr* entry = new (Z) CatchBlockEntryInstr(
       TokenPosition::kNoSource,  // Token position of catch block.
-      false,                     // Not an artifact of compilation.
+      is_synthesized,  // whether catch block was synthesized by FE compiler
       AllocateBlockId(), CurrentTryIndex(), graph_entry_, handler_types,
       handler_index, *CurrentException(), *CurrentStackTrace(),
       needs_stacktrace, GetNextDeoptId(), should_restore_closure_context);

runtime/vm/compiler/frontend/kernel_to_il.h

@@ -731,7 +731,8 @@ class FlowGraphBuilder : public BaseFlowGraphBuilder {
   Fragment BooleanNegate();
   Fragment CatchBlockEntry(const Array& handler_types,
                            intptr_t handler_index,
-                           bool needs_stacktrace);
+                           bool needs_stacktrace,
+                           bool is_synthesized);
   Fragment TryCatch(int try_handler_index);
   Fragment CheckStackOverflowInPrologue(TokenPosition position);
   Fragment CheckStackOverflow(TokenPosition position);

runtime/vm/kernel_binary.h

@@ -19,7 +19,7 @@ namespace kernel {
 // Keep in sync with package:kernel/lib/binary/tag.dart.
 
 static const uint32_t kMagicProgramFile = 0x90ABCDEFu;
-static const uint32_t kBinaryFormatVersion = 4;
+static const uint32_t kBinaryFormatVersion = 5;
 
 // Keep in sync with package:kernel/lib/binary/tag.dart
 #define KERNEL_TAG_LIST(V)                                                     \