e4a3b434d7
@Kha The transition has begun :) I found and fixed a few bugs, but it is going well so far.
42 lines
1.3 KiB
Text
42 lines
1.3 KiB
Text
-- From @joehendrix
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-- The imul doesn't type check as Lean won't try to coerce from a reg (bv 64) to a expr (bv ?u)
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new_frontend
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inductive MCType
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| bv : Nat → MCType
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open MCType
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inductive Reg : MCType → Type
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| rax (n : Nat) : Reg (bv n)
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inductive Expr : MCType → Type
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| r : ∀{tp:MCType}, Reg tp → Expr tp
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| sextC {s:Nat} (x : Expr (bv s)) (t:Nat) : Expr (bv t)
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instance reg_is_expr {tp:MCType} : Coe (Reg tp) (Expr tp) := ⟨Expr.r⟩
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def bvmul {w:Nat} (x y : Expr (bv w)) : Expr (bv w) := x
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/-
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Remark: Joe's original example used the following definition.
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```
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def sext {s:Nat} (x : Expr (bv s)) (t:Nat) : Expr (bv t) := Expr.sextC x t
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```
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This definition is bad because the parameter `s` is unconstrained.
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Type class resolution gets stuck at
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```
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CoeT (Reg (bv 64)) (Reg.rax 64) (Expr (bv ?m_1))
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```
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It would have to set `?m_1 := 64` which is not allowed since TC should
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not change external TC metavariables.
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I fixed the problem by changing the definition. Now,
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type inference will enforce that `?m_1` must be 64, and TC will be able
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to synthesize the instance.
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-/
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def sext {s:Nat} (x : Expr (bv s)) (n:Nat) : Expr (bv (s+n)) := Expr.sextC x (s+n)
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open MCType
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variables {u:Nat} (e : Expr (bv 64))
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#check (bvmul (sext (Reg.rax 64) 64) (sext e _) : Expr (bv 128))
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