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chore: simplify decide (b = true) and variants (#3426)

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```
@[simp] theorem decide_eq_true {b : Bool} : decide (b = true) = b := by cases b <;> simp
@[simp] theorem decide_eq_false {b : Bool} : decide (b = false) = !b := by cases b <;> simp
@[simp] theorem decide_true_eq {b : Bool} : decide (true = b) = b := by cases b <;> simp
@[simp] theorem decide_false_eq {b : Bool} : decide (false = b) = !b := by cases b <;> simp
```
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Scott Morrison 2024-02-21 15:30:25 +11:00 • committed by GitHub
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src/Init/Data/Bool.lean
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@ -48,6 +48,11 @@ theorem ne_false_iff : {b : Bool} → b ≠ false ↔ b = true := by decide
theorem eq_iff_iff {a b : Bool} : a = b ↔ (a ↔ b) := by cases b <;> simp
@[simp] theorem decide_eq_true {b : Bool} : decide (b = true) = b := by cases b <;> simp
@[simp] theorem decide_eq_false {b : Bool} : decide (b = false) = !b := by cases b <;> simp
@[simp] theorem decide_true_eq {b : Bool} : decide (true = b) = b := by cases b <;> simp
@[simp] theorem decide_false_eq {b : Bool} : decide (false = b) = !b := by cases b <;> simp
/-! ### and -/
@[simp] theorem not_and_self : ∀ (x : Bool), (!x && x) = false := by decide