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In general the tool favors strong typing, but it backs off to object if it means introducing something that would break the build.  There are several possible causes of weak typing:

  • Explicit use of weak typing using one variable for multiple types; typing typically a variable declared As Variant, As Object, As Form, As Control used for for multiple types; also occurs for a variable used as a scalar and an Array
  • using the VB6 CallByName function, 
  • using IF or Select based on TypeName or TypeOf function
  • using As Any
  • use of variant for dynamic arrays
  • Weakly typed symbols in a COM API description
  • Errors in the code that do not show up in VB6 for some reason
  • Unintended typing variations that are glossed over by VB6 but block unambiguous type inference
  • Timing issues wherein the type of a symbol is known too late in the translation process to assist with recognizing code that references the symbol
  • Depending on a type from a COM API that is not explicitly referenced in the VBP (i.e. CreateObject)
  • Depending on a type based on a variable expression (i.e. CreateObject)

Having said that, gmStudio provides an extensive set of upgrade configuration tools rules and techniques that teams may use to improve type inference:
  • Pre-Edits to change weak declarations to strong ones
  • Refactor/Fixtype commands to set the type of specific symbols based on fully-qualified identifier
  • Explicitly referencing a COM description that was not referenced by the VBP (i.e. helps with CreateObject)
  • Registry type="FixType" to set the type of a class of symbols based on their name
  • Modifying COM descriptions to set the types of various symbols
  • Activating the Generic Collections upgrade feature
  • Adding gmSL routines that help the tool recognize, interpret, and rework specific weak-typing scenarios
  • Setting a symbol to type="dynamic". But be warned, that does not really solve type inference issues, it merely simplifies late call syntax
  • Selects that alter type inference behavior at a global level
     

There are a few more advanced techniques to allow for symbols that are used with multiple-types and even to introduce interfaces or generics where type object or variant was used before.