Parameters must be of exported types

[Helpdesk]

When compiling a module TypeExports which imports a module M1 both directly and indirectly (via module M2), an error message is incorrectly reported:

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  Line  Col
     5   25 Error: parameters must be of exported types

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MODULE TypeExports;

IMPORT M2, M1;

PROCEDURE Test*(r: M1.R);
END Test;

END TypeExports.

Where M1 and M2 are:

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MODULE M1;

  TYPE
    R* = RECORD END;

END M1.

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MODULE M2;

  IMPORT M1;

  PROCEDURE P*(r: M1.R);
  END P;

END M2.

TypeExports compiles without an error if the order of the imports is changed to:

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IMPORT M1, M2;

[cfbsoftware]

This problem will be fixed in the next maintenance release. During investigation it was discovered that there are possible legitimate use cases of exported procedures with parameters of private types. For example:

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MODULE PrivateType;

IMPORT M;

VAR
  value: INTEGER;

BEGIN
  ASSERT(M.IsDefined(M.r));
  value := M.Value(M.r) 
END PrivateType.

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MODULE M;

  TYPE
    R = RECORD value: INTEGER; defined: BOOLEAN END;

  VAR
    r*: R;
    
  PROCEDURE IsDefined*(r: R): BOOLEAN;
    RETURN r.defined
  END IsDefined;

  PROCEDURE Value*(r: R): INTEGER;
    RETURN r.value
  END Value;
  
BEGIN
  r.defined := FALSE 
END M.

Consequently the severity of the resulting messages will be downgraded from errors to warnings:

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  compiling M

  Line  Col
     9   29 Warning: parameter type is not exported
    13   25 Warning: parameter type is not exported