Assert shape of the bound tree

Author: Julien Couvreur

src/Compilers/CSharp/Portable/BoundTree/BoundNodes.xml

@@ -95,12 +95,7 @@
   <AbstractNode Name="BoundEarlyValuePlaceholderBase" Base="BoundValuePlaceholderBase">
   </AbstractNode>
 
-  <!--
-  This node will not survive the local rewriting,
-  except in some scenarios in a Linq Expression Tree when the containing node
-  survives.
-  -->
-  <Node Name="BoundValuePlaceholder" Base="BoundValuePlaceholderBase">
+  <Node Name="BoundValuePlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
   </Node>
 
   <!--
@@ -113,9 +108,9 @@
 
   <!--
   This node is used to represent an expression returning value of a certain type.
-  It is used to perform intermediate binding, and will not survive the local rewriting.
+  It is used to perform intermediate binding.
   -->
-  <Node Name="BoundDeconstructValuePlaceholder" Base="BoundValuePlaceholderBase">
+  <Node Name="BoundDeconstructValuePlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
     <Field Name="VariableSymbol" Type="Symbol?"/>
     <Field Name="IsDiscardExpression" Type="bool" Null="NotApplicable"/>
@@ -124,24 +119,22 @@
   <!--
   In a tuple binary operator, this node is used to represent tuple elements in a tuple binary
   operator, and to represent an element-wise comparison result to convert back to bool.
-  It does not survive the initial binding.
   -->
-  <Node Name="BoundTupleOperandPlaceholder" Base="BoundValuePlaceholderBase">
+  <Node Name="BoundTupleOperandPlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="InitialBinding">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
   <!--
   This node is used to represent an awaitable expression of a certain type, when binding an using-await statement.
   -->
-  <Node Name="BoundAwaitableValuePlaceholder" Base="BoundValuePlaceholderBase">
+  <Node Name="BoundAwaitableValuePlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="StateMachineRewriting">
     <Field Name="Type" Type="TypeSymbol?" Override="true" Null="allow"/>
   </Node>
 
   <!--
   This node is used to represent an expression of a certain type, when attempting to bind its pattern dispose method
-  It does not survive past initial binding.
   -->
-  <Node Name="BoundDisposableValuePlaceholder" Base="BoundValuePlaceholderBase">
+  <Node Name="BoundDisposableValuePlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="InitialBinding">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
@@ -156,29 +149,29 @@
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
-  <!-- This node is used to represent the receiver for an implicit Index or Range indexer. It does not survive lowering -->
-  <Node Name="BoundImplicitIndexerReceiverPlaceholder" Base="BoundValuePlaceholderBase">
+  <!-- This node is used to represent the receiver for an implicit Index or Range indexer. -->
+  <Node Name="BoundImplicitIndexerReceiverPlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
     <Field Name="IsEquivalentToThisReference" Type="bool" PropertyOverrides="true"/>
   </Node>
 
-  <!-- This node represents the receiver for a list pattern. It does not survive lowering -->
-  <Node Name="BoundListPatternReceiverPlaceholder" Base="BoundEarlyValuePlaceholderBase">
+  <!-- This node represents the receiver for a list pattern. -->
+  <Node Name="BoundListPatternReceiverPlaceholder" Base="BoundEarlyValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
-  <!-- This node represents the Index value of accessing an element in a list pattern. It does not survive lowering -->
-  <Node Name="BoundListPatternIndexPlaceholder" Base="BoundEarlyValuePlaceholderBase">
+  <!-- This node represents the Index value of accessing an element in a list pattern. -->
+  <Node Name="BoundListPatternIndexPlaceholder" Base="BoundEarlyValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
-  <!-- This node represents the receiver for a slice pattern. It does not survive lowering -->
-  <Node Name="BoundSlicePatternReceiverPlaceholder" Base="BoundEarlyValuePlaceholderBase">
+  <!-- This node represents the receiver for a slice pattern. -->
+  <Node Name="BoundSlicePatternReceiverPlaceholder" Base="BoundEarlyValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
-  <!-- This node represents the Range value of accessing a range in a slice pattern. It does not survive lowering -->
-  <Node Name="BoundSlicePatternRangePlaceholder" Base="BoundEarlyValuePlaceholderBase">
+  <!-- This node represents the Range value of accessing a range in a slice pattern. -->
+  <Node Name="BoundSlicePatternRangePlaceholder" Base="BoundEarlyValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
   </Node>
 
@@ -393,9 +386,8 @@
     <Field Name="IsManaged" Type="bool"/>  
   </Node>
   <!-- Represents an AddressOf operator that has not yet been assigned to a
-       target-type. It has no natural type, and should not survive initial binding
-       except in error cases that are observable via the SemanticModel. -->
-  <Node Name="BoundUnconvertedAddressOfOperator" Base="BoundExpression">
+       target-type. It has no natural type. -->
+  <Node Name="BoundUnconvertedAddressOfOperator" Base="BoundExpression" DoesNotSurvive="InitialBinding">
     <Field Name="Operand" Type="BoundMethodGroup"/>
     <!-- Type is null. -->
     <Field Name="Type" Type="TypeSymbol?" Override="true" Null="always"/>
@@ -637,7 +629,7 @@
     <Field Name="RightOperand" Type="BoundExpression" />
   </Node>
 
-  <Node Name="BoundUnconvertedConditionalOperator" Base="BoundExpression">
+  <Node Name="BoundUnconvertedConditionalOperator" Base="BoundExpression" DoesNotSurvive="InitialBinding">
     <!-- Type is null. -->
     <Field Name="Type" Type="TypeSymbol?" Override="true" Null="always"/>
 
@@ -694,7 +686,7 @@
     <Field Name="Expression" Type="BoundExpression"/>
   </Node>
 
-  <Node Name="BoundAwaitableInfo" Base="BoundNode" HasValidate="true">
+  <Node Name="BoundAwaitableInfo" Base="BoundNode" HasValidate="true" DoesNotSurvive="StateMachineRewriting">
     <!-- Used to refer to the awaitable expression in GetAwaiter -->
     <Field Name="AwaitableInstancePlaceholder" Type="BoundAwaitableValuePlaceholder?" Null="allow" />
     <Field Name="IsDynamic" Type="bool"/>
@@ -709,7 +701,7 @@
     <Field Name="RuntimeAsyncAwaitCallPlaceholder" Type="BoundAwaitableValuePlaceholder?" Null="allow"/>
   </Node>
 
-  <Node Name="BoundAwaitExpression" Base="BoundExpression">
+  <Node Name="BoundAwaitExpression" Base="BoundExpression" DoesNotSurvive="StateMachineRewriting">
     <!-- Non-null type is required for this node kind -->
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow"/>
 
@@ -843,7 +835,7 @@
   Default literals can convert to the target type.
   Does not survive initial lowering.
   -->
-   <Node Name="BoundDefaultLiteral" Base="BoundExpression">
+   <Node Name="BoundDefaultLiteral" Base="BoundExpression" DoesNotSurvive="LocalRewriting">
     <!-- Type is null. -->
     <Field Name="Type" Type="TypeSymbol?" Override="true" Null="always"/>
   </Node>
@@ -1130,7 +1122,7 @@
   Bound node that represents a local function declaration:
     void Foo() { }
   -->
-  <Node Name="BoundLocalFunctionStatement" Base="BoundStatement">
+  <Node Name="BoundLocalFunctionStatement" Base="BoundStatement" DoesNotSurvive="ClosureConversion">
     <!-- Must be a LocalFunctionSymbol until the node reaches LocalRewriter -->
     <Field Name="Symbol" Type="MethodSymbol"/>
     <Field Name="BlockBody" Type="BoundBlock?"/>
@@ -1161,11 +1153,11 @@
     <Field Name="Checked" Type="bool"/>
   </Node>
 
-  <Node Name="BoundYieldReturnStatement" Base="BoundStatement">
+  <Node Name="BoundYieldReturnStatement" Base="BoundStatement" DoesNotSurvive="StateMachineRewriting">
     <Field Name="Expression" Type="BoundExpression" Null="disallow"/>
   </Node>
 
-  <Node Name="BoundYieldBreakStatement" Base="BoundStatement"/>
+  <Node Name="BoundYieldBreakStatement" Base="BoundStatement" DoesNotSurvive="StateMachineRewriting"/>
 
   <Node Name="BoundThrowStatement" Base="BoundStatement">
     <Field Name="ExpressionOpt" Type="BoundExpression?"/>
@@ -1223,7 +1215,7 @@
     <Field Name="LengthBasedStringSwitchDataOpt" Type="LengthBasedStringSwitchData?" />
   </Node>
 
-  <Node Name="BoundIfStatement" Base="BoundStatement">
+  <Node Name="BoundIfStatement" Base="BoundStatement" DoesNotSurvive="LocalRewriting">
     <Field Name="Condition" Type="BoundExpression"/>
     <Field Name="Consequence" Type="BoundStatement"/>
     <Field Name="AlternativeOpt" Type="BoundStatement?"/>
@@ -1292,7 +1284,7 @@
     <Field Name="TargetPlaceholder" Type="BoundDeconstructValuePlaceholder" Null="disallow"/>
   </Node>
 
-  <Node Name="BoundUsingStatement" Base="BoundStatement">
+  <Node Name="BoundUsingStatement" Base="BoundStatement" DoesNotSurvive="LocalRewriting">
     <!-- DeclarationsOpt and ExpressionOpt cannot both be non-null. -->
     <Field Name="Locals" Type="ImmutableArray&lt;LocalSymbol&gt;"/>
     <Field Name="DeclarationsOpt" Type="BoundMultipleLocalDeclarations?"/>
@@ -1529,7 +1521,7 @@
     <Field Name="Label" Type="LabelSymbol" Null="disallow"/>
   </Node>
 
-  <Node Name="BoundUnconvertedSwitchExpression" Base="BoundSwitchExpression">
+  <Node Name="BoundUnconvertedSwitchExpression" Base="BoundSwitchExpression" DoesNotSurvive="InitialBinding">
   </Node>
 
   <!-- 
@@ -1881,9 +1873,8 @@
 
   <!--
   This node is used to represent a target-typed object creation expression
-  It does not survive past initial binding.
   -->
-  <Node Name="BoundUnconvertedObjectCreationExpression" Base="BoundExpression">
+  <Node Name="BoundUnconvertedObjectCreationExpression" Base="BoundExpression" DoesNotSurvive="InitialBinding">
     <!-- Type is not significant for this node type; always null -->
     <Field Name="Type" Type="TypeSymbol?" Override="true" Null="always"/>
     <Field Name="Arguments" Type="ImmutableArray&lt;BoundExpression&gt;"/>
@@ -1927,9 +1918,8 @@
 
   <!--
   An unconverted collection expression.
-  It does not survive past initial binding.
   -->
-  <Node Name="BoundUnconvertedCollectionExpression" Base="BoundCollectionExpressionBase">
+  <Node Name="BoundUnconvertedCollectionExpression" Base="BoundCollectionExpressionBase" DoesNotSurvive="InitialBinding">
     <!-- Type is not significant for this node type; always null -->
     <Field Name="Type" Type="TypeSymbol?" Override="true" Null="always"/>
   </Node>
@@ -1990,7 +1980,7 @@
   Once converted to a target type, they cannot be target-typed again.
   The tuple literal is one which has not been converted to a target type.
   -->
-  <Node Name="BoundTupleLiteral" Base="BoundTupleExpression">
+  <Node Name="BoundTupleLiteral" Base="BoundTupleExpression" DoesNotSurvive="InitialBinding">
     <!-- 
     It is possible for a tuple to not have a type in a literal form
     Ex: 
@@ -2345,9 +2335,9 @@
 
   <!-- 
   Special node to encapsulate initializers added into a constructor. 
-  Helps to do special optimizations in lowering, doesn't survive the lowering.
+  Helps to do special optimizations in lowering.
   -->
-  <Node Name="BoundTypeOrInstanceInitializers" Base="BoundStatementList">
+  <Node Name="BoundTypeOrInstanceInitializers" Base="BoundStatementList" DoesNotSurvive="LocalRewriting">
   </Node>
 
   <Node Name="BoundNameOfOperator" Base="BoundExpression">
@@ -2365,19 +2355,19 @@
     <Field Name="ConstantValueOpt" Type="ConstantValue?" PropertyOverrides="true"/>
   </AbstractNode>
 
-  <Node Name="BoundUnconvertedInterpolatedString" Base="BoundInterpolatedStringBase">
+  <Node Name="BoundUnconvertedInterpolatedString" Base="BoundInterpolatedStringBase" DoesNotSurvive="InitialBinding">
   </Node>
 
   <Node Name="BoundInterpolatedString" Base="BoundInterpolatedStringBase">
     <Field Name="InterpolationData" Type="InterpolatedStringHandlerData?"/>
   </Node>
 
-  <Node Name="BoundInterpolatedStringHandlerPlaceholder" Base="BoundValuePlaceholderBase"/>
+  <Node Name="BoundInterpolatedStringHandlerPlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="LocalRewriting"/>
 
   <!-- A typed expression placeholder for the arguments to the constructor call for an interpolated string handler
        conversion. We intentionally use a placeholder for overload resolution here to ensure that no conversion
-       from expression can occur. This node is only used for intermediate binding and does not survive local rewriting. -->
-  <Node Name="BoundInterpolatedStringArgumentPlaceholder" Base="BoundValuePlaceholderBase">
+       from expression can occur. -->
+  <Node Name="BoundInterpolatedStringArgumentPlaceholder" Base="BoundValuePlaceholderBase" DoesNotSurvive="LocalRewriting">
     <Field Name="Type" Type="TypeSymbol" Override="true" Null="disallow" />
     <!-- The index in the containing member of the argument this is the placeholder for. Should be a positive number or
          one of the constants in the other part of the partial class. -->
@@ -2573,7 +2563,7 @@
   <Node Name="OutVariablePendingInference" Base="VariablePendingInference" />
 
   <!-- The node is transformed into BoundLocal or BoundFieldAccess after inference -->
-  <Node Name="DeconstructionVariablePendingInference" Base="VariablePendingInference" />
+  <Node Name="DeconstructionVariablePendingInference" Base="VariablePendingInference" DoesNotSurvive="LocalRewriting" />
 
   <!-- The node is transformed into BoundDeconstructValuePlaceholder after inference -->
   <Node Name="OutDeconstructVarPendingInference" Base="BoundExpression">

src/Compilers/CSharp/Portable/Compiler/MethodCompiler.cs

@@ -791,6 +791,7 @@ private void CompileSynthesizedMethods(TypeCompilationState compilationState)
                         }
 
                         SetGlobalErrorIfTrue(diagnosticsThisMethod.HasAnyErrors());
+                        PipelinePhaseValidator.Assert(loweredBody, PipelinePhase.StateMachineRewriting);
 
                         if (_emitMethodBodies && !diagnosticsThisMethod.HasAnyErrors() && !_globalHasErrors)
                         {
@@ -1499,6 +1500,8 @@ internal static BoundStatement LowerBodyOrInitializer(
                 return body;
             }
 
+            PipelinePhaseValidator.Assert(body, PipelinePhase.InitialBinding);
+
             try
             {
                 var loweredBody = LocalRewriter.Rewrite(
@@ -1585,6 +1588,8 @@ internal static BoundStatement LowerBodyOrInitializer(
                     return bodyWithoutLambdas;
                 }
 
+                PipelinePhaseValidator.Assert(bodyWithoutLambdas, PipelinePhase.ClosureConversion);
+
                 BoundStatement bodyWithoutIterators = IteratorRewriter.Rewrite(bodyWithoutLambdas, method, methodOrdinal, stateMachineStateDebugInfoBuilder, lazyVariableSlotAllocator, compilationState, diagnostics,
                     out IteratorStateMachine iteratorStateMachine);
 
@@ -1608,6 +1613,8 @@ internal static BoundStatement LowerBodyOrInitializer(
                 Debug.Assert(iteratorStateMachine is null || asyncStateMachine is null);
                 stateMachineTypeOpt = (StateMachineTypeSymbol)iteratorStateMachine ?? asyncStateMachine;
 
+                PipelinePhaseValidator.Assert(bodyWithoutAsync, PipelinePhase.StateMachineRewriting);
+
                 return bodyWithoutAsync;
             }
             catch (BoundTreeVisitor.CancelledByStackGuardException ex)

src/Compilers/CSharp/Portable/Generated/BoundNodes.xml.Generated.cs

@@ -66,7 +66,7 @@ internal static BoundStatement Rewrite(
                     method.GetFirstLocation());
 
                 stateMachineType = null;
-                return bodyWithAwaitLifted;
+                return (BoundStatement)bodyWithAwaitLifted.WithHasErrors();
             }
 
             // The CLR doesn't support adding fields to structs, so in order to enable EnC in an async method we need to generate a class.
@@ -82,7 +82,7 @@ internal static BoundStatement Rewrite(
 
             if (!rewriter.VerifyPresenceOfRequiredAPIs())
             {
-                return bodyWithAwaitLifted;
+                return (BoundStatement)bodyWithAwaitLifted.WithHasErrors();
             }
 
             try

src/Compilers/CSharp/Portable/Lowering/AsyncRewriter/AsyncRewriter.cs

@@ -120,7 +120,7 @@ private RuntimeAsyncRewriter(SyntheticBoundNodeFactory factory, IReadOnlySet<Sym
             _factory.Diagnostics.Add(ErrorCode.ERR_UnsupportedFeatureInRuntimeAsync,
                 node.Syntax.Location,
                 _factory.CurrentFunction);
-            return node;
+            return node.WithHasErrors();
         }
 
         var runtimeAsyncAwaitCall = awaitableInfo.RuntimeAsyncAwaitCall;

src/Compilers/CSharp/Portable/Lowering/AsyncRewriter/RuntimeAsyncRewriter.cs

@@ -86,7 +86,7 @@ internal static BoundStatement Rewrite(
             var rewriter = new IteratorRewriter(body, method, isEnumerable, stateMachineType, stateMachineStateDebugInfoBuilder, slotAllocatorOpt, compilationState, diagnostics);
             if (!rewriter.VerifyPresenceOfRequiredAPIs())
             {
-                return body;
+                return (BoundStatement)body.WithHasErrors();
             }
 
             return rewriter.Rewrite();