module Typecheck (typeCheckExp, typeCheckStm, typeCheckVar) where
+
import Abssyntax
import Control.Monad.State
import Data.Map as Map
if with else: 1 conflict
An if statement before the else could be reduced to an if statement lacking the else, but the correct thing is to shift it onto the stack.
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+
+typing rules
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+
+(t is little tau, T is large tau, E is 'in', and + is that other symbol)
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+
+
+[Eq, Neq]
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+e:bool <= e1:t & e2:t
+where e is e1 Eq e2.
+
+
+[Plus, Minus, Times, Div]
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+e:int <= e1:int & e2:int
+where e is e1 Plus e2.
+
+
+[Lt, ELt, Gt, EGt]
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+e:bool <= e1:int & e2:int
+where e is e1 Lt e2.
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+
+[Assignment]
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+T+ i := e:t <= i:t E T & T+ e:t
+where the assignment is identifier i = expression e.
+
+
+[ExpT]
+
+u,e:t <= e:t & u:t
+where the expression is type u expression e.
+
+
+[ENeg]
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+e:int <= e:int
+
+
+[ENot]
+
+e:bool <= e:bool
+
+
+[SExp, SBlock]
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+S:NoType <= e:t
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+
+[SIf]
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+T+ if e then s1 else s2 <= T+ e:bool & T+ s1 & T+ s2
+
+
+[SWhile]
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+T+ while e do s <= T+ e:bool & T+ s
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+
+[SDecl]
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+T+ i:t => T', i:t <= i!ET & e:t & u:t
+
+(Type u Ident i = Exp e)
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