diff --git a/pkg/compiler/lib/src/inferrer/builder_kernel.dart b/pkg/compiler/lib/src/inferrer/builder_kernel.dart
index ac087dd97d7..3f7d25c02a2 100644
--- a/pkg/compiler/lib/src/inferrer/builder_kernel.dart
+++ b/pkg/compiler/lib/src/inferrer/builder_kernel.dart
@@ -322,4 +322,10 @@ class KernelTypeGraphBuilder extends ir.Visitor<TypeInformation> {
         receiverType, _analyzedMember, arguments, _sideEffects,
         inLoop: inLoop, isConditional: false);
   }
+
+  @override
+  TypeInformation visitLet(ir.Let node) {
+    visit(node.variable);
+    return visit(node.body);
+  }
 }
diff --git a/tests/compiler/dart2js/equivalence/id_equivalence.dart b/tests/compiler/dart2js/equivalence/id_equivalence.dart
index a3b0fac317c..2dc5ffa57d7 100644
--- a/tests/compiler/dart2js/equivalence/id_equivalence.dart
+++ b/tests/compiler/dart2js/equivalence/id_equivalence.dart
@@ -345,7 +345,9 @@ abstract class AstDataExtractor extends ast.Visitor with DataRegistry {
             computeForNode(node, createUpdateId(position));
           }
           break;
+        case SendStructureKind.PREFIX:
         case SendStructureKind.POSTFIX:
+        case SendStructureKind.COMPOUND:
           computeForNode(node, createAccessId(node.selector));
           computeForNode(node, createInvokeId(node.assignmentOperator));
           computeForNode(node, createUpdateId(node.selector));
@@ -425,17 +427,20 @@ abstract class IrDataExtractor extends ir.Visitor with DataRegistry {
   }
 
   NodeId computeDefaultNodeId(ir.TreeNode node) {
-    assert(node.fileOffset != ir.TreeNode.noOffset);
+    assert(node.fileOffset != ir.TreeNode.noOffset,
+        "No fileOffset on $node (${node.runtimeType})");
     return new NodeId(node.fileOffset, IdKind.node);
   }
 
   NodeId createInvokeId(ir.TreeNode node) {
-    assert(node.fileOffset != ir.TreeNode.noOffset);
+    assert(node.fileOffset != ir.TreeNode.noOffset,
+        "No fileOffset on ${node} (${node.runtimeType})");
     return new NodeId(node.fileOffset, IdKind.invoke);
   }
 
   NodeId createUpdateId(ir.TreeNode node) {
-    assert(node.fileOffset != ir.TreeNode.noOffset);
+    assert(node.fileOffset != ir.TreeNode.noOffset,
+        "No fileOffset on ${node} (${node.runtimeType})");
     return new NodeId(node.fileOffset, IdKind.update);
   }
 
@@ -469,7 +474,8 @@ abstract class IrDataExtractor extends ir.Visitor with DataRegistry {
   }
 
   visitVariableDeclaration(ir.VariableDeclaration node) {
-    if (node.parent is! ir.FunctionDeclaration) {
+    if (node.name != null && node.parent is! ir.FunctionDeclaration) {
+      // Skip synthetic variables and function declaration variables.
       computeForNode(node, computeDefaultNodeId(node));
     }
     super.visitVariableDeclaration(node);
@@ -486,7 +492,10 @@ abstract class IrDataExtractor extends ir.Visitor with DataRegistry {
   }
 
   visitVariableGet(ir.VariableGet node) {
-    computeForNode(node, computeDefaultNodeId(node));
+    if (node.variable.name != null) {
+      // Skip use of synthetic variables.
+      computeForNode(node, computeDefaultNodeId(node));
+    }
     super.visitVariableGet(node);
   }
 
@@ -496,7 +505,10 @@ abstract class IrDataExtractor extends ir.Visitor with DataRegistry {
   }
 
   visitVariableSet(ir.VariableSet node) {
-    computeForNode(node, createUpdateId(node));
+    if (node.variable.name != null) {
+      // Skip use of synthetic variables.
+      computeForNode(node, createUpdateId(node));
+    }
     super.visitVariableSet(node);
   }
 
diff --git a/tests/compiler/dart2js/equivalence/id_equivalence_helper.dart b/tests/compiler/dart2js/equivalence/id_equivalence_helper.dart
index c9b36793c4e..8b965442edf 100644
--- a/tests/compiler/dart2js/equivalence/id_equivalence_helper.dart
+++ b/tests/compiler/dart2js/equivalence/id_equivalence_helper.dart
@@ -292,6 +292,8 @@ Map<Id, IdValue> computeExpectedMap(AnnotatedCode code) {
   Map<Id, IdValue> map = <Id, IdValue>{};
   for (Annotation annotation in code.annotations) {
     IdValue idValue = IdValue.decode(annotation.offset, annotation.text);
+    Expect.isFalse(map.containsKey(idValue.id),
+        "Duplicate annotations for ${idValue.id}.");
     map[idValue.id] = idValue;
   }
   return map;
diff --git a/tests/compiler/dart2js/equivalence/id_equivalence_test.dart b/tests/compiler/dart2js/equivalence/id_equivalence_test.dart
index 1d9ee218d21..1ed42e30d4f 100644
--- a/tests/compiler/dart2js/equivalence/id_equivalence_test.dart
+++ b/tests/compiler/dart2js/equivalence/id_equivalence_test.dart
@@ -182,7 +182,9 @@ class ResolvedAstComputer extends AstDataExtractor with ComputerMixin {
           String dynamicName = getDynamicName();
           if (dynamicName != null) return computeSetName(dynamicName);
           break;
+        case SendStructureKind.PREFIX:
         case SendStructureKind.POSTFIX:
+        case SendStructureKind.COMPOUND:
           String dynamicName = getDynamicName();
           if (dynamicName != null) {
             if (id.kind == IdKind.update) {
diff --git a/tests/compiler/dart2js/inference/data/locals.dart b/tests/compiler/dart2js/inference/data/locals.dart
index 4ef0128215a..1e0839f28ea 100644
--- a/tests/compiler/dart2js/inference/data/locals.dart
+++ b/tests/compiler/dart2js/inference/data/locals.dart
@@ -9,6 +9,10 @@ main() {
   updatedLocal();
   invokeLocal();
   postfixLocal();
+  postfixLocalUsed();
+  prefixLocal();
+  prefixLocalUsed();
+  complexAssignmentLocal();
 }
 
 /*element: uninitializedLocal:[null]*/
@@ -44,3 +48,29 @@ postfixLocal() {
   local2 /*invoke: [exact=JSUInt31]*/ ++;
   return null;
 }
+
+/*element: postfixLocalUsed:[exact=JSUInt31]*/
+postfixLocalUsed() {
+  var local2 = 0;
+  return local2 /*invoke: [exact=JSUInt31]*/ ++;
+}
+
+/*element: prefixLocal:[null]*/
+prefixLocal() {
+  // ignore: UNUSED_LOCAL_VARIABLE
+  var local2 = 0;
+  /*invoke: [exact=JSUInt31]*/ ++local2;
+  return null;
+}
+
+/*element: prefixLocalUsed:[subclass=JSUInt32]*/
+prefixLocalUsed() {
+  var local2 = 0;
+  return /*invoke: [exact=JSUInt31]*/ ++local2;
+}
+
+/*element: complexAssignmentLocal:[subclass=JSUInt32]*/
+complexAssignmentLocal() {
+  var local2 = 0;
+  return local2 /*invoke: [exact=JSUInt31]*/ += 42;
+}