Create life-time regions for flow captures in Control Flow Graph. (#28100)

Create Control Flow Graph regions to designate life-time of flow captures in a Control Flow Graph. A region should start as soon as a capture is needed to accurately represent the order of evaluation within operations involving control of flow. However, it should not start too soon. For example, if there is a branch that represents an execution path that bypasses the use of a capture completely, that branch should not be included into the region for the capture. Also, the region should end as soon as the last operation referencing the capture is reached.

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IAddressOfOperation.cs

@@ -76,51 +76,59 @@ unsafe void M(bool x, S2* p1, S2* p2, int* p3)
 Block[B0] - Entry
     Statements (0)
     Next (Regular) Block[B1]
-Block[B1] - Block
-    Predecessors: [B0]
-    Statements (1)
-        IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'p3')
-          Value: 
-            IParameterReferenceOperation: p3 (OperationKind.ParameterReference, Type: System.Int32*) (Syntax: 'p3')
-
-    Jump if False (Regular) to Block[B3]
-        IParameterReferenceOperation: x (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'x')
-
-    Next (Regular) Block[B2]
-Block[B2] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'p1')
-          Value: 
-            IParameterReferenceOperation: p1 (OperationKind.ParameterReference, Type: S2*) (Syntax: 'p1')
+        Entering: {R1}
 
-    Next (Regular) Block[B4]
-Block[B3] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'p2')
-          Value: 
-            IParameterReferenceOperation: p2 (OperationKind.ParameterReference, Type: S2*) (Syntax: 'p2')
-
-    Next (Regular) Block[B4]
-Block[B4] - Block
-    Predecessors: [B2] [B3]
-    Statements (1)
-        IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'p3 = &(x ? p1 : p2)->i;')
-          Expression: 
-            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32*) (Syntax: 'p3 = &(x ? p1 : p2)->i')
-              Left: 
-                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32*, IsImplicit) (Syntax: 'p3')
-              Right: 
-                IAddressOfOperation (OperationKind.AddressOf, Type: System.Int32*) (Syntax: '&(x ? p1 : p2)->i')
-                  Reference: 
-                    IFieldReferenceOperation: System.Int32 S2.i (OperationKind.FieldReference, Type: System.Int32) (Syntax: '(x ? p1 : p2)->i')
-                      Instance Receiver: 
-                        IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: '(x ? p1 : p2)')
-                          Children(1):
-                              IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: S2*, IsImplicit) (Syntax: 'x ? p1 : p2')
+.locals {R1}
+{
+    CaptureIds: [0] [1]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'p3')
+              Value: 
+                IParameterReferenceOperation: p3 (OperationKind.ParameterReference, Type: System.Int32*) (Syntax: 'p3')
+
+        Jump if False (Regular) to Block[B3]
+            IParameterReferenceOperation: x (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'x')
+
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'p1')
+              Value: 
+                IParameterReferenceOperation: p1 (OperationKind.ParameterReference, Type: S2*) (Syntax: 'p1')
+
+        Next (Regular) Block[B4]
+    Block[B3] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'p2')
+              Value: 
+                IParameterReferenceOperation: p2 (OperationKind.ParameterReference, Type: S2*) (Syntax: 'p2')
+
+        Next (Regular) Block[B4]
+    Block[B4] - Block
+        Predecessors: [B2] [B3]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'p3 = &(x ? p1 : p2)->i;')
+              Expression: 
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32*) (Syntax: 'p3 = &(x ? p1 : p2)->i')
+                  Left: 
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32*, IsImplicit) (Syntax: 'p3')
+                  Right: 
+                    IAddressOfOperation (OperationKind.AddressOf, Type: System.Int32*) (Syntax: '&(x ? p1 : p2)->i')
+                      Reference: 
+                        IFieldReferenceOperation: System.Int32 S2.i (OperationKind.FieldReference, Type: System.Int32) (Syntax: '(x ? p1 : p2)->i')
+                          Instance Receiver: 
+                            IOperation:  (OperationKind.None, Type: null, IsImplicit) (Syntax: '(x ? p1 : p2)')
+                              Children(1):
+                                  IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: S2*, IsImplicit) (Syntax: 'x ? p1 : p2')
+
+        Next (Regular) Block[B5]
+            Leaving: {R1}
+}
 
-    Next (Regular) Block[B5]
 Block[B5] - Exit
     Predecessors: [B4]
     Statements (0)

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IAwaitExpression.cs

-// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
@@ -292,63 +292,71 @@ static async Task M(bool b, int i)
 Block[B0] - Entry
     Statements (0)
     Next (Regular) Block[B1]
-Block[B1] - Block
-    Predecessors: [B0]
-    Statements (1)
-        IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
-          Value: 
-            IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'i')
+        Entering: {R1}
 
-    Jump if False (Regular) to Block[B3]
-        IParameterReferenceOperation: b (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'b')
+.locals {R1}
+{
+    CaptureIds: [0] [1]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
+              Value: 
+                IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'i')
+
+        Jump if False (Regular) to Block[B3]
+            IParameterReferenceOperation: b (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'b')
+
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'await M2(2)')
+              Value: 
+                IAwaitOperation (OperationKind.Await, Type: System.Int32) (Syntax: 'await M2(2)')
+                  Expression: 
+                    IInvocationOperation (System.Threading.Tasks.Task<System.Int32> C.M2(System.Int32 i)) (OperationKind.Invocation, Type: System.Threading.Tasks.Task<System.Int32>) (Syntax: 'M2(2)')
+                      Instance Receiver: 
+                        null
+                      Arguments(1):
+                          IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: '2')
+                            ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 2) (Syntax: '2')
+                            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
 
-    Next (Regular) Block[B2]
-Block[B2] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'await M2(2)')
-          Value: 
-            IAwaitOperation (OperationKind.Await, Type: System.Int32) (Syntax: 'await M2(2)')
-              Expression: 
-                IInvocationOperation (System.Threading.Tasks.Task<System.Int32> C.M2(System.Int32 i)) (OperationKind.Invocation, Type: System.Threading.Tasks.Task<System.Int32>) (Syntax: 'M2(2)')
-                  Instance Receiver: 
-                    null
-                  Arguments(1):
-                      IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: '2')
-                        ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 2) (Syntax: '2')
-                        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-
-    Next (Regular) Block[B4]
-Block[B3] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'await M2(3)')
-          Value: 
-            IAwaitOperation (OperationKind.Await, Type: System.Int32) (Syntax: 'await M2(3)')
+        Next (Regular) Block[B4]
+    Block[B3] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'await M2(3)')
+              Value: 
+                IAwaitOperation (OperationKind.Await, Type: System.Int32) (Syntax: 'await M2(3)')
+                  Expression: 
+                    IInvocationOperation (System.Threading.Tasks.Task<System.Int32> C.M2(System.Int32 i)) (OperationKind.Invocation, Type: System.Threading.Tasks.Task<System.Int32>) (Syntax: 'M2(3)')
+                      Instance Receiver: 
+                        null
+                      Arguments(1):
+                          IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: '3')
+                            ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3) (Syntax: '3')
+                            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+
+        Next (Regular) Block[B4]
+    Block[B4] - Block
+        Predecessors: [B2] [B3]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i = b ? awa ... wait M2(3);')
               Expression: 
-                IInvocationOperation (System.Threading.Tasks.Task<System.Int32> C.M2(System.Int32 i)) (OperationKind.Invocation, Type: System.Threading.Tasks.Task<System.Int32>) (Syntax: 'M2(3)')
-                  Instance Receiver: 
-                    null
-                  Arguments(1):
-                      IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: '3')
-                        ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3) (Syntax: '3')
-                        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-
-    Next (Regular) Block[B4]
-Block[B4] - Block
-    Predecessors: [B2] [B3]
-    Statements (1)
-        IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i = b ? awa ... wait M2(3);')
-          Expression: 
-            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'i = b ? awa ... await M2(3)')
-              Left: 
-                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i')
-              Right: 
-                IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'b ? await M ... await M2(3)')
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'i = b ? awa ... await M2(3)')
+                  Left: 
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i')
+                  Right: 
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'b ? await M ... await M2(3)')
+
+        Next (Regular) Block[B5]
+            Leaving: {R1}
+}
 
-    Next (Regular) Block[B5]
 Block[B5] - Exit
     Predecessors: [B4]
     Statements (0)
@@ -380,54 +388,62 @@ static async Task M(bool b, int i)
 Block[B0] - Entry
     Statements (0)
     Next (Regular) Block[B1]
-Block[B1] - Block
-    Predecessors: [B0]
-    Statements (1)
-        IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
-          Value: 
-            IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'i')
-
-    Jump if False (Regular) to Block[B3]
-        IParameterReferenceOperation: b (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'b')
-
-    Next (Regular) Block[B2]
-Block[B2] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: '2')
-          Value: 
-            ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 2) (Syntax: '2')
-
-    Next (Regular) Block[B4]
-Block[B3] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: '3')
-          Value: 
-            ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3) (Syntax: '3')
+        Entering: {R1}
 
-    Next (Regular) Block[B4]
-Block[B4] - Block
-    Predecessors: [B2] [B3]
-    Statements (1)
-        IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i = await M2(b ? 2 : 3);')
-          Expression: 
-            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'i = await M2(b ? 2 : 3)')
-              Left: 
-                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i')
-              Right: 
-                IAwaitOperation (OperationKind.Await, Type: System.Int32) (Syntax: 'await M2(b ? 2 : 3)')
-                  Expression: 
-                    IInvocationOperation (System.Threading.Tasks.Task<System.Int32> C.M2(System.Int32 i)) (OperationKind.Invocation, Type: System.Threading.Tasks.Task<System.Int32>) (Syntax: 'M2(b ? 2 : 3)')
-                      Instance Receiver: 
-                        null
-                      Arguments(1):
-                          IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: 'b ? 2 : 3')
-                            IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'b ? 2 : 3')
-                            InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                            OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+.locals {R1}
+{
+    CaptureIds: [0] [1]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
+              Value: 
+                IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'i')
+
+        Jump if False (Regular) to Block[B3]
+            IParameterReferenceOperation: b (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'b')
+
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: '2')
+              Value: 
+                ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 2) (Syntax: '2')
+
+        Next (Regular) Block[B4]
+    Block[B3] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: '3')
+              Value: 
+                ILiteralOperation (OperationKind.Literal, Type: System.Int32, Constant: 3) (Syntax: '3')
+
+        Next (Regular) Block[B4]
+    Block[B4] - Block
+        Predecessors: [B2] [B3]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i = await M2(b ? 2 : 3);')
+              Expression: 
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'i = await M2(b ? 2 : 3)')
+                  Left: 
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i')
+                  Right: 
+                    IAwaitOperation (OperationKind.Await, Type: System.Int32) (Syntax: 'await M2(b ? 2 : 3)')
+                      Expression: 
+                        IInvocationOperation (System.Threading.Tasks.Task<System.Int32> C.M2(System.Int32 i)) (OperationKind.Invocation, Type: System.Threading.Tasks.Task<System.Int32>) (Syntax: 'M2(b ? 2 : 3)')
+                          Instance Receiver: 
+                            null
+                          Arguments(1):
+                              IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: 'b ? 2 : 3')
+                                IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'b ? 2 : 3')
+                                InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                                OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+
+        Next (Regular) Block[B5]
+            Leaving: {R1}
+}
 
-    Next (Regular) Block[B5]
 Block[B5] - Exit
     Predecessors: [B4]
     Statements (0)

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IConstructorBodyOperation.cs

@@ -874,56 +874,81 @@ class C
 Block[B0] - Entry
     Statements (0)
     Next (Regular) Block[B1]
-Block[B1] - Block
-    Predecessors: [B0]
-    Statements (2)
-        IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: ': this(i ?? j)')
-          Value: 
-            IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsImplicit) (Syntax: ': this(i ?? j)')
+        Entering: {R1}
 
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
-          Value: 
-            IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32?) (Syntax: 'i')
+.locals {R1}
+{
+    CaptureIds: [0] [2]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: ': this(i ?? j)')
+              Value: 
+                IInstanceReferenceOperation (ReferenceKind: ContainingTypeInstance) (OperationKind.InstanceReference, Type: C, IsImplicit) (Syntax: ': this(i ?? j)')
 
-    Jump if True (Regular) to Block[B3]
-        IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'i')
-          Operand: 
-            IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32?, IsImplicit) (Syntax: 'i')
+        Next (Regular) Block[B2]
+            Entering: {R2}
 
-    Next (Regular) Block[B2]
-Block[B2] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
-          Value: 
-            IInvocationOperation ( System.Int32 System.Int32?.GetValueOrDefault()) (OperationKind.Invocation, Type: System.Int32, IsImplicit) (Syntax: 'i')
-              Instance Receiver: 
-                IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32?, IsImplicit) (Syntax: 'i')
-              Arguments(0)
+    .locals {R2}
+    {
+        CaptureIds: [1]
+        Block[B2] - Block
+            Predecessors: [B1]
+            Statements (1)
+                IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
+                  Value: 
+                    IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32?) (Syntax: 'i')
 
-    Next (Regular) Block[B4]
-Block[B3] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'j')
-          Value: 
-            IParameterReferenceOperation: j (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'j')
+            Jump if True (Regular) to Block[B4]
+                IIsNullOperation (OperationKind.IsNull, Type: System.Boolean, IsImplicit) (Syntax: 'i')
+                  Operand: 
+                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32?, IsImplicit) (Syntax: 'i')
+                Leaving: {R2}
 
-    Next (Regular) Block[B4]
-Block[B4] - Block
-    Predecessors: [B2] [B3]
-    Statements (2)
-        IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsImplicit) (Syntax: ': this(i ?? j)')
-          Expression: 
-            IInvocationOperation ( C..ctor(System.Int32 i)) (OperationKind.Invocation, Type: System.Void) (Syntax: ': this(i ?? j)')
-              Instance Receiver: 
-                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: C, IsImplicit) (Syntax: ': this(i ?? j)')
-              Arguments(1):
-                  IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: 'i ?? j')
-                    IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i ?? j')
-                    InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+            Next (Regular) Block[B3]
+        Block[B3] - Block
+            Predecessors: [B2]
+            Statements (1)
+                IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
+                  Value: 
+                    IInvocationOperation ( System.Int32 System.Int32?.GetValueOrDefault()) (OperationKind.Invocation, Type: System.Int32, IsImplicit) (Syntax: 'i')
+                      Instance Receiver: 
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int32?, IsImplicit) (Syntax: 'i')
+                      Arguments(0)
+
+            Next (Regular) Block[B5]
+                Leaving: {R2}
+    }
+
+    Block[B4] - Block
+        Predecessors: [B2]
+        Statements (1)
+            IFlowCaptureOperation: 2 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'j')
+              Value: 
+                IParameterReferenceOperation: j (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'j')
 
+        Next (Regular) Block[B5]
+    Block[B5] - Block
+        Predecessors: [B3] [B4]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null, IsImplicit) (Syntax: ': this(i ?? j)')
+              Expression: 
+                IInvocationOperation ( C..ctor(System.Int32 i)) (OperationKind.Invocation, Type: System.Void) (Syntax: ': this(i ?? j)')
+                  Instance Receiver: 
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: C, IsImplicit) (Syntax: ': this(i ?? j)')
+                  Arguments(1):
+                      IArgumentOperation (ArgumentKind.Explicit, Matching Parameter: i) (OperationKind.Argument, Type: null) (Syntax: 'i ?? j')
+                        IFlowCaptureReferenceOperation: 2 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i ?? j')
+                        InConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                        OutConversion: CommonConversion (Exists: True, IsIdentity: True, IsNumeric: False, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+
+        Next (Regular) Block[B6]
+            Leaving: {R1}
+}
+
+Block[B6] - Block
+    Predecessors: [B5]
+    Statements (1)
         IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'p = k;')
           Expression: 
             ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'p = k')
@@ -932,9 +957,9 @@ class C
               Right: 
                 IParameterReferenceOperation: k (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'k')
 
-    Next (Regular) Block[B5]
-Block[B5] - Exit
-    Predecessors: [B4]
+    Next (Regular) Block[B7]
+Block[B7] - Exit
+    Predecessors: [B6]
     Statements (0)
 ");
         }

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IConversionExpression.cs

@@ -5117,49 +5117,57 @@ void M(int i, bool b, long l, long m)
 Block[B0] - Entry
     Statements (0)
     Next (Regular) Block[B1]
-Block[B1] - Block
-    Predecessors: [B0]
-    Statements (1)
-        IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
-          Value: 
-            IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'i')
-
-    Jump if False (Regular) to Block[B3]
-        IParameterReferenceOperation: b (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'b')
-
-    Next (Regular) Block[B2]
-Block[B2] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'l')
-          Value: 
-            IParameterReferenceOperation: l (OperationKind.ParameterReference, Type: System.Int64) (Syntax: 'l')
-
-    Next (Regular) Block[B4]
-Block[B3] - Block
-    Predecessors: [B1]
-    Statements (1)
-        IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'm')
-          Value: 
-            IParameterReferenceOperation: m (OperationKind.ParameterReference, Type: System.Int64) (Syntax: 'm')
+        Entering: {R1}
+
+.locals {R1}
+{
+    CaptureIds: [0] [1]
+    Block[B1] - Block
+        Predecessors: [B0]
+        Statements (1)
+            IFlowCaptureOperation: 0 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'i')
+              Value: 
+                IParameterReferenceOperation: i (OperationKind.ParameterReference, Type: System.Int32) (Syntax: 'i')
+
+        Jump if False (Regular) to Block[B3]
+            IParameterReferenceOperation: b (OperationKind.ParameterReference, Type: System.Boolean) (Syntax: 'b')
+
+        Next (Regular) Block[B2]
+    Block[B2] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'l')
+              Value: 
+                IParameterReferenceOperation: l (OperationKind.ParameterReference, Type: System.Int64) (Syntax: 'l')
 
-    Next (Regular) Block[B4]
-Block[B4] - Block
-    Predecessors: [B2] [B3]
-    Statements (1)
-        IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i = (int) (b ? l : m);')
-          Expression: 
-            ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'i = (int) (b ? l : m)')
-              Left: 
-                IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i')
-              Right: 
-                IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32) (Syntax: '(int) (b ? l : m)')
-                  Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
-                    (ExplicitNumeric)
-                  Operand: 
-                    IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int64, IsImplicit) (Syntax: 'b ? l : m')
+        Next (Regular) Block[B4]
+    Block[B3] - Block
+        Predecessors: [B1]
+        Statements (1)
+            IFlowCaptureOperation: 1 (OperationKind.FlowCapture, Type: null, IsImplicit) (Syntax: 'm')
+              Value: 
+                IParameterReferenceOperation: m (OperationKind.ParameterReference, Type: System.Int64) (Syntax: 'm')
+
+        Next (Regular) Block[B4]
+    Block[B4] - Block
+        Predecessors: [B2] [B3]
+        Statements (1)
+            IExpressionStatementOperation (OperationKind.ExpressionStatement, Type: null) (Syntax: 'i = (int) (b ? l : m);')
+              Expression: 
+                ISimpleAssignmentOperation (OperationKind.SimpleAssignment, Type: System.Int32) (Syntax: 'i = (int) (b ? l : m)')
+                  Left: 
+                    IFlowCaptureReferenceOperation: 0 (OperationKind.FlowCaptureReference, Type: System.Int32, IsImplicit) (Syntax: 'i')
+                  Right: 
+                    IConversionOperation (TryCast: False, Unchecked) (OperationKind.Conversion, Type: System.Int32) (Syntax: '(int) (b ? l : m)')
+                      Conversion: CommonConversion (Exists: True, IsIdentity: False, IsNumeric: True, IsReference: False, IsUserDefined: False) (MethodSymbol: null)
+                        (ExplicitNumeric)
+                      Operand: 
+                        IFlowCaptureReferenceOperation: 1 (OperationKind.FlowCaptureReference, Type: System.Int64, IsImplicit) (Syntax: 'b ? l : m')
+
+        Next (Regular) Block[B5]
+            Leaving: {R1}
+}
 
-    Next (Regular) Block[B5]
 Block[B5] - Exit
     Predecessors: [B4]
     Statements (0)

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IDeclarationExpression.cs

@@ -57,6 +57,7 @@ public void M2(out int i)
 .locals {R1}
 {
     Locals: [var i1] [var i2]
+    CaptureIds: [0]
     Block[B1] - Block
         Predecessors: [B0]
         Statements (0)

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_INameOfOperation.cs

@@ -132,6 +132,7 @@ void M(bool b, int i1, int i2)
 .locals {R1}
 {
     Locals: [System.String test]
+    CaptureIds: [0]
     Block[B1] - Block
         Predecessors: [B0]
         Statements (0)

src/Compilers/Core/Portable/Collections/ArrayBuilderExtensions.cs

@@ -20,6 +20,18 @@ public static bool Any<T>(this ArrayBuilder<T> builder, Func<T, bool> predicate)
             return false;
         }
 
+        public static bool Any<T, A>(this ArrayBuilder<T> builder, Func<T, A, bool> predicate, A arg)
+        {
+            foreach (var item in builder)
+            {
+                if (predicate(item, arg))
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+
         public static bool All<T>(this ArrayBuilder<T> builder, Func<T, bool> predicate)
         {
             foreach (var item in builder)

src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.Context.cs

@@ -17,23 +17,23 @@ internal struct Context
         {
             public readonly IOperation ImplicitInstance;
             public readonly INamedTypeSymbol AnonymousType;
-            public readonly ImmutableArray<KeyValuePair<IPropertySymbol, int>> AnonymousTypePropertyCaptureIds;
+            public readonly ImmutableArray<KeyValuePair<IPropertySymbol, IOperation>> AnonymousTypePropertyValues;
 
-            internal Context(IOperation implicitInstance, INamedTypeSymbol anonymousType, ImmutableArray<KeyValuePair<IPropertySymbol, int>> anonymousTypePropertyCaptureIds)
+            internal Context(IOperation implicitInstance, INamedTypeSymbol anonymousType, ImmutableArray<KeyValuePair<IPropertySymbol, IOperation>> anonymousTypePropertyValues)
             {
-                Debug.Assert(!anonymousTypePropertyCaptureIds.IsDefault);
+                Debug.Assert(!anonymousTypePropertyValues.IsDefault);
                 Debug.Assert(implicitInstance == null || anonymousType == null);
                 ImplicitInstance = implicitInstance;
                 AnonymousType = anonymousType;
-                AnonymousTypePropertyCaptureIds = anonymousTypePropertyCaptureIds;
+                AnonymousTypePropertyValues = anonymousTypePropertyValues;
             }
         }
 
         private Context GetCurrentContext()
         {
             return new Context(_currentImplicitInstance.ImplicitInstance, _currentImplicitInstance.AnonymousType,
-                               _currentImplicitInstance.AnonymousTypePropertyCaptureIds?.ToImmutableArray() ?? 
-                                   ImmutableArray<KeyValuePair<IPropertySymbol, int>>.Empty);
+                               _currentImplicitInstance.AnonymousTypePropertyValues?.ToImmutableArray() ?? 
+                                   ImmutableArray<KeyValuePair<IPropertySymbol, IOperation>>.Empty);
         }
 
         private void SetCurrentContext(in Context context)

src/Compilers/Core/Portable/Operations/ControlFlowRegionKind.cs

@@ -15,9 +15,10 @@ public enum ControlFlowRegionKind
         Root,
 
         /// <summary>
-        /// Region with the only purpose to represent the life-time of locals and nested methods (local functions, lambdas).
+        /// Region with the only purpose to represent the life-time of locals, intermediate results, and nested methods (local functions, lambdas).
         /// The lifetime of a local variable is the portion of program execution during which storage is guaranteed to be reserved for it.
         /// The lifetime of a nested method is the portion of program execution within which the method can be referenced.
+        /// The lifetime of an intermediate result (capture) is the portion of program execution within which the result can be referenced.
         /// </summary>
         LocalLifetime,