Control flow analysis broken for never returning class methods #56812

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1. MartinJohns commented on Dec 17, 2023

   

   Martin Johns (MartinJohns)

   on Dec 17, 2023

   Last edited by MartinJohns

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   This is working as intended. For performance reasons only specific calls are analyzed. Check #32695 for details.

   If you change your code according to the requirements it works:

    const c: Class = new Class();
    if (!arg) {
      c.throwMethod();
    }

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2. jcalz commented on Dec 17, 2023

   

   Joe Calzaretta (jcalz)

   on Dec 17, 2023

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   Also duplicates #46254

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3. gordonmleigh commented on Dec 17, 2023

   

   Gordon Leigh (gordonmleigh)

   on Dec 17, 2023

   Last edited by gordonmleigh

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   Martin Johns (@MartinJohns) thanks for the quick reply.

   Relevant quote from #32695 is:

   A function call is analyzed as an assertion call or never-returning call when

   • the call occurs as a top-level expression statement, and
   • the call specifies a single identifier or a dotted sequence of identifiers for the function name, and
   • each identifier in the function name references an entity with an explicit type, and
   • the function name resolves to a function type with an asserts return type or an explicit never return type annotation.

   Another workaround is as follows:

   function repro1(arg: string | undefined): number {
     if (!arg) {
       // compatible with return type because the type is `never`, even if the CFA doesn't work
       return new Class().throwMethod();
     }
     return arg.length;
   }
4. Gordon Leigh (gordonmleigh)

   closed this as completedon Dec 17, 2023
5. microsoft

   locked as resolved and limited conversation to collaborators on Oct 22, 2025