Identify null primitive constants in the debug scopes

SteveGilham · Sep 10, 2022 · 5834548 · 5834548
1 parent c4bfd8b
commit 5834548
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diff --git a/AltCover.Engine/CecilEx.fs b/AltCover.Engine/CecilEx.fs
@@ -13,6 +13,7 @@ open System.Reflection
 
 open Mono.Cecil
 open Mono.Cecil.Cil
+open Mono.Cecil.Metadata
 
 module AssemblyConstants =
   let internal nugetCache =
@@ -190,12 +191,38 @@ module internal CecilExtension =
        System.Reflection.BindingFlags.Instance
        ||| System.Reflection.BindingFlags.NonPublic)
 
+  let etypeField =
+    typeof<TypeReference>.GetField
+      ("etype",
+       System.Reflection.BindingFlags.Instance
+       ||| System.Reflection.BindingFlags.NonPublic)
+
   let internal offsetTable =
     System.Collections.Generic.SortedDictionary<int, Instruction>()
 
   let unresolved (point: InstructionOffset) =
     isResolvedProp.GetValue(point) :?> bool |> not
 
+  let checkScopeConstants (m: MethodDefinition) =
+    scopesSeen
+    |> Seq.iter(fun scope -> let sus = scope.Constants
+                                       |> Seq.filter (fun c -> (isNull c.Value) &&
+                                                               match etypeField.GetValue(c.ConstantType) :?> byte with
+                                                               | 0x14uy // ElementType.Array
+                                                               | 0x1duy // ElementType.SzArray
+                                                               | 0x12uy // ElementType.Class
+                                                               | 0x1cuy // ElementType.Object
+                                                               | 0x00uy // ElementType.None
+                                                               | 0x13uy // ElementType.Var
+                                                               | 0x1euy // ElementType.MVar
+                                                               | 0x0euy // ElementType.String
+                                                                   -> false
+                                                               | _ -> true)
+                                      |> Seq.toList
+                             sus |> Seq.iter (fun c -> scope.Constants.Remove c |> ignore
+                                                       sprintf "Null Primitive Constant %s in method %s" c.Name m.FullName
+                                                       |> Output.warn))
+
   let prepareLocalScopes (m: MethodDefinition) =
     offsetTable.Clear()
     scopesSeen.Clear()
@@ -238,6 +265,9 @@ module internal CecilExtension =
             scope.End <- resolvePoint scope.End
 
     m.DebugInformation.Scope |> resolveScope
+
+    checkScopeConstants m
+
     pruneLocalScopes m
 
   // Adjust the IL for exception handling

diff --git a/AltCover.Tests/Tests2.fs b/AltCover.Tests/Tests2.fs
@@ -923,8 +923,14 @@ has been prefixed with Ldc_I4_1 (1 byte)
 
     let size = finish.Offset + finish.GetSize()
 
+    let f = pathGetterDef.Body.Instructions.[2].Operand :?> FieldDefinition
+    let primitive = f.FieldType
+    let np = ArrayType(primitive, 23)
+
     pathGetterDef.DebugInformation.Scope <- rescope
 
+    let bexpect = System.Text.StringBuilder()
+
     [ -1
       4
       finish.Offset
@@ -935,10 +941,22 @@ has been prefixed with Ldc_I4_1 (1 byte)
       let s = ScopeDebugInformation(start, null)
       s.Start <- InstructionOffset(i)
       s.End <- InstructionOffset(size)
+      let n = i.ToString().Replace("-", "_")
+      s.Constants.Add <| ConstantDebugInformation("I"+n, primitive, null)
+      s.Constants.Add <| ConstantDebugInformation("A"+n, np, null)
+
+      sprintf "Null Primitive Constant I%s in method System.Boolean Sample31.Class3/Class4::get_Defer()" n
+      |> bexpect.AppendLine
+      |> ignore
       rescope.Scopes.Add s)
 
     rescope.Scopes.Add rescope
 
+    let save = Output.warn
+    let b = System.Text.StringBuilder()
+
+    Output.warn <- b.AppendLine >> ignore
+
     prepareLocalScopes pathGetterDef
 
     Assert.True(
@@ -966,6 +984,9 @@ has been prefixed with Ldc_I4_1 (1 byte)
       |> Seq.toList
 
     test <@ result = expected @>
+    test <@ b.ToString() = bexpect.ToString() @>
+
+    Output.warn <- save
 
   [<Test>]
   let ShouldWriteMonoAssemblyOK () =