Order explicit type args by constraint dependencies before unifying - #20342
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A generic value/method with a subtype constraint that references a later type parameter (Register<'a,'b when 'a :> I<'b>>) failed with FS0001 when the argument implements the interface at several instantiations. The explicit type arguments are now unified in dependency order so a parameter referenced by another's constraint is solved first. Fixes #20103 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 8ce30fb9-238f-4bb2-8f31-71e8d173c2ca
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…not-call-method-with-a-generic-interf-d02fa6 # Conflicts: # src/Compiler/Facilities/LanguageFeatures.fs # src/Compiler/Facilities/LanguageFeatures.fsi
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Add equal-arity competing overloads with explicit selection assertions and explicit/inferred type arguments. Verify dependency ordering and rollback through red-green and a failed-candidate undo mutation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 137c3de0-8937-4b62-aff3-13ce91c4cdcb
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Fixes #20103
A generic value or method whose subtype constraint references a later type parameter (
Register<'a, 'b when 'a :> I<'b>>) failed with FS0001 when the supplied argument implemented the interface at more than one instantiation (I<int>andI<string>): the explicit type arguments were unified left-to-right, so'a := Foore-solved'a :> I<'b>while'bwas still unknown and greedily committed it to the wrong instantiation. Explicit type arguments are now unified in constraint-dependency order, so a parameter referenced by another's constraint is solved first. Behind a language-version 11.0 flag; a genuine dependency cycle degrades to the previous left-to-right order.