(*  Title:      HOL/MicroJava/J/WellForm.thy

    ID:         $Id$

    Author:     David von Oheimb

    Copyright   1999 Technische Universitaet Muenchen

Well-formedness of Java programs

for static checks on expressions and statements, see WellType.thy

improvements over Java Specification 1.0 (cf. 8.4.6.3, 8.4.6.4, 9.4.1):

* a method implementing or overwriting another method may have a result type 

  that widens to the result type of the other method (instead of identical type)

simplifications:

* for uniformity, Object is assumed to be declared like any other class

*)

WellForm = TypeRel +

types 'c wtm = 'c prog => cname => 'c mdecl => bool

constdefs

 wf_fdecl	:: "'c prog \\<Rightarrow>          fdecl \\<Rightarrow> bool"

"wf_fdecl G \\<equiv> \\<lambda>(fn,ft). is_type G ft"

 wf_mhead	:: "'c prog \\<Rightarrow> sig   \\<Rightarrow> ty \\<Rightarrow> bool"

"wf_mhead G \\<equiv> \\<lambda>(mn,pTs) rT. (\\<forall>T\\<in>set pTs. is_type G T) \\<and> is_type G rT"

 wf_mdecl	:: "'c wtm \\<Rightarrow> 'c wtm"

"wf_mdecl wtm G C \\<equiv> \\<lambda>(sig,rT,mb). wf_mhead G sig rT \\<and> wtm G C (sig,rT,mb)"

  wf_cdecl	:: "'c wtm \\<Rightarrow> 'c prog \\<Rightarrow> 'c cdecl \\<Rightarrow> bool"

"wf_cdecl wtm G \\<equiv>

   \\<lambda>(C,(sc,fs,ms)).

	(\\<forall>f\\<in>set fs. wf_fdecl G   f    ) \\<and>  unique fs \\<and>

	(\\<forall>m\\<in>set ms. wf_mdecl wtm G C m) \\<and>  unique ms \\<and>

	(case sc of None \\<Rightarrow> C = Object

         | Some D \\<Rightarrow>

             is_class G D \\<and>  \\<not>  G\\<turnstile>D\\<prec>C C \\<and>

             (\\<forall>(sig,rT,b)\\<in>set ms. \\<forall>D' rT' b'.

                 method(G,D) sig = Some(D',rT',b') \\<longrightarrow> G\\<turnstile>rT\\<preceq>rT'))"

 wf_prog	:: "'c wtm \\<Rightarrow> 'c prog \\<Rightarrow> bool"

"wf_prog wtm G \\<equiv>

   let cs = set G in ObjectC \\<in> cs \\<and> (\\<forall>c\\<in>cs. wf_cdecl wtm G c) \\<and> unique G"

end