[cfe] Dot Shorthands: Fix bug with property fileOffsets.

Surfaced from this co19 test crashing because of an assert when making a null-aware element. The `fileOffset` for static tearoffs and static gets were not being properly set and caused the crash. This CL simply sets the `fileOffset` on those expressions and existing tests should pass.

https://github.com/dart-lang/co19/blob/2c7f9a6a379cfc49b3e9019d1f616d7ec9edd766/LanguageFeatures/Static-access-shorthand/non_ambiguity_A02_t01.dart

Bug: #59758
Change-Id: I7b81f0ee11d8a9458154f1148e92523d1ad8be99
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/420840
Reviewed-by: Chloe Stefantsova <[email protected]>
Commit-Queue: Kallen Tu <[email protected]>

Author: kallentu

pkg/front_end/lib/src/type_inference/inference_visitor.dart

@@ -12284,18 +12284,21 @@ class InferenceVisitorImpl extends InferenceVisitorBase
     ExpressionInferenceResult expressionInferenceResult;
     switch (member) {
       case Field():
-        expressionInferenceResult =
-            inferExpression(new StaticGet(member), cachedContext);
+        Expression staticGet = new StaticGet(member)
+          ..fileOffset = node.fileOffset;
+        expressionInferenceResult = inferExpression(staticGet, cachedContext);
       case Procedure():
         if (member.isGetter) {
-          expressionInferenceResult =
-              inferExpression(new StaticGet(member), cachedContext);
+          Expression staticGet = new StaticGet(member)
+            ..fileOffset = node.fileOffset;
+          expressionInferenceResult = inferExpression(staticGet, cachedContext);
         } else {
           // Method tearoffs.
           DartType type =
               member.function.computeFunctionType(Nullability.nonNullable);
-          return instantiateTearOff(
-              type, typeContext, new StaticTearOff(member));
+          Expression tearOff = new StaticTearOff(member)
+            ..fileOffset = node.fileOffset;
+          return instantiateTearOff(type, typeContext, tearOff);
         }
       case Constructor():
       case null:
@@ -12317,13 +12320,15 @@ class InferenceVisitorImpl extends InferenceVisitorBase
           if (constructor is Constructor) {
             DartType type = constructor.function
                 .computeFunctionType(Nullability.nonNullable);
-            return instantiateTearOff(
-                type, typeContext, new ConstructorTearOff(constructor));
+            Expression tearOff = new ConstructorTearOff(constructor)
+              ..fileOffset = node.fileOffset;
+            return instantiateTearOff(type, typeContext, tearOff);
           } else if (constructor is Procedure) {
             DartType type = constructor.function
                 .computeFunctionType(Nullability.nonNullable);
-            return instantiateTearOff(
-                type, typeContext, new StaticTearOff(constructor));
+            Expression tearOff = new StaticTearOff(constructor)
+              ..fileOffset = node.fileOffset;
+            return instantiateTearOff(type, typeContext, tearOff);
           }
         }