X-Git-Url: http://git.joshuawise.com/snipe.git/blobdiff_plain/12aa4087bee3e70f170d7457794921de4e385227..6ade8b0a3251e44b34c6bdbbd9403e36d6fd6231:/type/typechecker.sml diff --git a/type/typechecker.sml b/type/typechecker.sml index 699d15a..63608bd 100644 --- a/type/typechecker.sml +++ b/type/typechecker.sml @@ -1,49 +1,243 @@ -(* L1 Compiler +(* L3 Compiler * TypeChecker * Author: Alex Vaynberg * Modified: Frank Pfenning - * - * Simple typechecker that is based on a unit Symbol.table - * This is all that is needed since there is only an integer type present + * Modified: Joshua Wise + * Modified: Chris Lu *) signature TYPE_CHECK = sig (* prints error message and raises ErrorMsg.error if error found *) - val typecheck : Ast.program -> unit + val typecheck : Ast.program -> Ast.program end; structure TypeChecker :> TYPE_CHECK = struct structure A = Ast + + datatype asn = ASSIGNED | UNASSIGNED - (* tc_exp : unit Symbol.table -> Ast.exp -> Mark.ext option -> unit *) - fun tc_exp env (A.Var(id)) ext = - (case Symbol.look env id - of NONE => ( ErrorMsg.error ext ("undefined variable `" ^ Symbol.name id ^ "'") ; - raise ErrorMsg.Error ) - | SOME _ => ()) - | tc_exp env (A.ConstExp(c)) ext = () - | tc_exp env (A.OpExp(oper,es)) ext = - (* Note: it is syntactically impossible in this language to - * apply an operator to an incorrect number of arguments - * so we only check each of the arguments - *) - List.app (fn e => tc_exp env e ext) es - | tc_exp env (A.Marked(marked_exp)) ext = - tc_exp env (Mark.data marked_exp) (Mark.ext marked_exp) + fun returns nil = false + | returns (A.Assign _ :: stms) = returns stms + | returns (A.Return _ :: stms) = true + | returns (A.Nop :: stms) = returns stms + | returns (A.Break :: stms) = true (* blah *) + | returns (A.Continue :: stms) = true (* blah *) + | returns (A.If (_, s1, NONE) :: stms) = returns stms + | returns (A.If (_, s1, SOME s2) :: stms) = (returns s1 andalso returns s2) orelse returns stms + | returns (A.For _ :: stms) = returns stms + | returns (A.While _ :: stms) = returns stms + | returns (A.MarkedStm m :: stms) = returns (Mark.kane m :: stms) + + fun breakcheck nil mark = () + | breakcheck (A.Break :: stms) mark = ( ErrorMsg.error mark ("Illegal break outside loop") ; + raise ErrorMsg.Error ) + | breakcheck (A.Continue :: stms) mark = ( ErrorMsg.error mark ("Illegal continue outside loop") ; + raise ErrorMsg.Error ) + | breakcheck (A.If (_, s1, NONE) :: stms) mark = + ( breakcheck s1 mark; + breakcheck stms mark) + | breakcheck (A.If (_, s1, SOME s2) :: stms) mark = + ( breakcheck s1 mark; + breakcheck s2 mark; + breakcheck stms mark) + | breakcheck (A.MarkedStm m :: stms) mark = (breakcheck [(Mark.kane m)] (Mark.ext m); breakcheck stms mark) + | breakcheck (_ :: stms) mark = breakcheck stms mark + + fun varcheck_exp env fenv (A.Var v) mark : Ast.vtype = + ( case Symbol.look env v + of NONE => ( ErrorMsg.error mark ("undefined variable `" ^ Symbol.name v ^ "'") ; + raise ErrorMsg.Error ) + | SOME (t, UNASSIGNED) => ( ErrorMsg.error mark ("usage of unassigned variable `" ^ Symbol.name v ^ "'") ; + raise ErrorMsg.Error ) + | SOME (t, ASSIGNED) => t) + | varcheck_exp env fenv (A.ConstExp _) mark = (A.Int) + | varcheck_exp env fenv (A.OpExp (_, l)) mark = (List.app (fn znt => (varcheck_exp env fenv znt mark; ())) l; A.Int) + | varcheck_exp env fenv (A.FuncCall (f, l)) mark = + let + val types = map (fn znt => varcheck_exp env fenv znt mark) l + val func = case Symbol.look fenv f + of NONE => ( ErrorMsg.error mark ("undefined function `" ^ Symbol.name f ^ "'") ; + raise ErrorMsg.Error ) + | SOME a => a + val (rtype, params) = case func + of A.Extern (rtype, _, params) => (rtype, params) + | A.Function (rtype, _, params, _, _) => (rtype, params) + val paramtypes = map (fn (i, t) => t) params + val () = if not (types = paramtypes) + then ( ErrorMsg.error mark ("incorrect parameters for function `" ^ Symbol.name f ^ "'") ; + raise ErrorMsg.Error ) + else () + in + rtype + end + | varcheck_exp env fenv (A.Marked m) mark = varcheck_exp env fenv (Mark.kane m) (Mark.ext m) + + fun computeassigns env nil = env + | computeassigns env (A.Assign (id,e) :: stms) = + computeassigns (Symbol.bind env (id, (A.Int, ASSIGNED))) stms + | computeassigns env (A.Return _ :: stms) = env + | computeassigns env (A.Nop :: stms) = computeassigns env stms + | computeassigns env (A.Break :: stms) = env + | computeassigns env (A.Continue :: stms) = env + | computeassigns env (A.If (e, s1, NONE) :: stms) = computeassigns env stms + | computeassigns env (A.If (e, s1, SOME s2) :: stms) = + let + val env1 = computeassigns env s1 + val env2 = computeassigns env s2 + val env' = + Symbol.intersect + (fn ((t, ASSIGNED), (t', ASSIGNED)) => (t, ASSIGNED) (* XXX check types for equality *) + | ((t, _), (t', _)) => (t, UNASSIGNED)) + (env1, env2) + val env' = + if (returns s1) then env2 + else if (returns s2) then env1 + else env' + in + computeassigns env' stms + end + | computeassigns env (A.While (e, s1) :: stms) = computeassigns env stms + | computeassigns env (A.For (sbegin, e, sloop, inner) :: stms) = + let + val env' = case sbegin + of SOME(s) => computeassigns env [s] + | NONE => env + in + computeassigns env' stms + end + | computeassigns env (A.MarkedStm m :: stms) = computeassigns env ((Mark.kane m) :: stms) + + fun varcheck env fenv nil mark = nil + | varcheck env fenv (A.Assign (id, e) :: stms) mark = + let + val sym = Symbol.look env id + val _ = if not (isSome sym) + then (ErrorMsg.error mark ("assignment to undeclared variable " ^ (Symbol.name id)); raise ErrorMsg.Error) + else () + val (t, a) = valOf sym + val t' = varcheck_exp env fenv e mark + in + A.Assign (id, e) :: (varcheck (Symbol.bind env (id, (t, ASSIGNED))) fenv stms mark) + end + | varcheck env fenv (A.Return (e) :: stms) mark = + ( varcheck_exp env fenv e mark; + A.Return (e) :: nil ) + | varcheck env fenv (A.Nop :: stms) mark = + ( A.Nop :: (varcheck env fenv stms mark)) + | varcheck env fenv (A.Break :: stms) mark = + ( A.Break :: nil ) + | varcheck env fenv (A.Continue :: stms) mark = + ( A.Continue :: nil ) + | varcheck env fenv (A.If (e, s1, NONE) :: stms) mark = + ( varcheck_exp env fenv e mark ; + varcheck env fenv s1 mark ; + A.If (e, s1, NONE) :: (varcheck env fenv stms mark) ) + | varcheck env fenv ((i as A.If (e, s1, SOME s2)) :: stms) mark = + ( varcheck_exp env fenv e mark ; + varcheck env fenv s1 mark ; + varcheck env fenv s2 mark ; + A.If (e, s1, SOME s2) :: + (if (returns [i]) + then nil + else varcheck (computeassigns env [i]) fenv stms mark) ) + | varcheck env fenv (A.While (e, s1) :: stms) mark = + ( varcheck_exp env fenv e mark ; + varcheck env fenv s1 mark ; + A.While (e, s1) :: (varcheck env fenv stms mark) ) + | varcheck env fenv (A.For (sbegin, e, sloop, inner) :: stms) mark = + let + val sbegin = case sbegin + of SOME(s) => SOME (hd (varcheck env fenv [s] mark)) + | NONE => NONE + val env' = case sbegin + of SOME(s) => computeassigns env [s] + | NONE => env + val _ = varcheck_exp env' fenv e + val inner = varcheck env' fenv inner mark + val env'' = computeassigns env' inner + val sloop = case sloop + of SOME(s) => SOME (hd (varcheck env'' fenv [s] mark)) + | NONE => NONE + in + A.For (sbegin, e, sloop, inner) :: (varcheck env' fenv stms mark) + end + | varcheck env fenv (A.MarkedStm m :: stms) mark = varcheck env fenv ((Mark.kane m) :: stms) (Mark.ext m) - (* tc_stms : unit Symbol.table -> Ast.program -> unit *) - fun tc_stms env nil = () - | tc_stms env (A.Assign(id,e)::stms) = - ( tc_exp env e NONE ; - tc_stms (Symbol.bind env (id, ())) stms ) - | tc_stms env (A.Return(e)::nil) = - tc_exp env e NONE - | tc_stms env (A.Return _ :: _) = - ( ErrorMsg.error NONE ("`return' not last statement") ; - raise ErrorMsg.Error ) + fun bindvars sym stat l = foldr (fn ((i,t), s) => Symbol.bind s (i,(t, stat))) sym l + fun bindfuns sym l = + foldr + (fn (a as (A.Function (_, id, _, _, _)), s) => Symbol.bind s (id, a) + | (a as (A.Extern (_, id, _)), s) => Symbol.bind s (id, a)) + sym l - fun typecheck prog = tc_stms Symbol.empty prog + fun dupchk l = + List.app + (fn (n, _) => + let + val name = Symbol.name n + val all = List.filter (fn (n', _) => name = (Symbol.name n')) l + val count = length all + in + if count = 1 + then () + else ( ErrorMsg.error NONE ("multiple definition of variable " ^ (Symbol.name n)); + raise ErrorMsg.Error ) + end) l + fun typecheck_fn p (e as (A.Extern (t, id, al))) = (dupchk al; e) + | typecheck_fn p (A.Function (t, id, al, vl, sl)) = + let + val () = breakcheck sl NONE + val () = if not (returns sl) + then ( ErrorMsg.error NONE ("function `"^ Symbol.name id ^ "' does not return in all cases"); + raise ErrorMsg.Error ) + else () + val env = Symbol.empty + val env = bindvars env ASSIGNED al + val env = bindvars env UNASSIGNED vl + val fenv = bindfuns Symbol.empty p + val () = dupchk (al @ vl) + in + A.Function (t, id, al, vl, varcheck env fenv sl NONE) + end + + fun typecheck p = + let + fun getFun n = + List.find (fn A.Extern (_, id, _) => ((Symbol.name id) = n) + | A.Function (_, id, _, _, _) => ((Symbol.name id) = n)) + p + val main = case (getFun "main") + of NONE => ( ErrorMsg.error NONE ("no function named main"); + raise ErrorMsg.Error ) + | SOME m => m + val () = case main + of A.Extern _ => ( ErrorMsg.error NONE ("you anus, main can't be an extern"); + raise ErrorMsg.Error ) + | A.Function (A.Int, _, nil, _, _) => () + | A.Function (A.Int, _, _, _, _) => ( ErrorMsg.error NONE ("main should take no parameters"); + raise ErrorMsg.Error ) + val () = List.app + (fn a => + let + val id = case a + of A.Extern (_, id, _) => id + | A.Function (_, id, _, _, _) => id + val name = Symbol.name id + val all = List.filter + (fn A.Extern (_, id, _) => (Symbol.name id) = name + | A.Function (_, id, _, _, _) => (Symbol.name id) = name) + p + val num = length all + in + if num = 1 + then () + else ( ErrorMsg.error NONE ("multiple definition of " ^ name); + raise ErrorMsg.Error ) + end) p + in + List.map (typecheck_fn p) p + end end