[ecosSystem]

Problem

AEval() and AEvalA() can't be called from a macro or script with a codeblock literal:

local a := {1,2}
aeval(a, {|x| x})    // error XM0205: No suitable overload of 'XSharp.RT.Functions.AEval()'

This also fails with the optional start/count arguments, and for a plain macro aeval({1,2}, {|x| x}). Passing a USUAL that holds a codeblock works, and so does AScan(), because its parameter is a USUAL.

Cause

The codeblock literal has the type XSharp.Codeblock, and the parameter has the type ICodeblock. In Binder.Conversion(), the reference conversion check uses Type.IsSubclassOf(). That method only looks at base classes and never at implemented interfaces. So no conversion was found, and every non-generic overload was rejected. The generic AEval<T> overloads are rejected anyway by the open-generic check.

Change

Binder.Conversion.cs: use IsAssignableFrom() instead of IsSubclassOf():

• for the implicit reference conversion (source type to base type or interface)
• for the reverse explicit conversion

For class to class conversions this gives the same result as before. The identity case is handled earlier by TypesMatch().

Tests

• ScriptTests.prg: four new tests:
  • aeval through Compile and through CompileCodeblock
  • aeval with start/count
  • aevala
• Harness: I also checked with a C# harness, in the VO and Core dialects, through both Compile and CompileCodeblock. All cases failed with XM0205 before the change and pass after it.
• MacroCompiler.Example run: I ran it with and without the change. The only difference in the results is the four new tests.
  • I couldn't build XSharp.VO/VFP/Rdd locally, so I commented out the few VO/VFP-only lines in VoTests.
  • The test run stops at DbCreate in the UDC tests in both runs, so the tests after that point did not run.
• Real application: the change was also tried in a real application that runs scripts through GetScriptCompiler() + CompileCodeblock(), together with MacroCompiler: nested codeblocks can use LOCALs of the enclosing script/codeblock #2113.

Relation to #2113

This fixes the AEval() side note in #2113. The two PRs are independent. Together, a script can use aeval(a, {|x| nSum += x}) with a LOCAL nSum. Both PRs add tests at the same place in ScriptTests.prg, so whichever one is merged second will have a trivial conflict there: keep both test blocks.

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