Documentation

Lean.Meta.InferType

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def Lean.Expr.instantiateBetaRevRange (e : Expr) (start stop : Nat) (args : Array Expr) :
Expr

Auxiliary function for instantiating the loose bound variables in e with args[start:stop]. This function is similar to instantiateRevRange, but it applies beta-reduction when we instantiate a bound variable with a lambda expression. Example: Given the term #0 a, and start := 0, stop := 1, args := #[fun x => x] the result is a instead of (fun x => x) a. This reduction is useful when we are inferring the type of eliminator-like applications. For example, given (n m : Nat) (f : Nat → Nat) (h : m = n), the type of Eq.subst (motive := fun x => f m = f x) h rfl is motive n which is (fun (x : Nat) => f m = f x) n This function reduces the new application to f m = f n

We use it to implement inferAppType

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partial def Lean.Expr.instantiateBetaRevRange.visit (start stop : Nat) (args : Array Expr) (e : Expr) (offset : Nat) :
MonadStateCacheT (ExprStructEq × Nat) Expr Id Expr
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def Lean.Meta.throwFunctionExpected {α : Type} (f : Expr) :
MetaM α
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def Lean.Meta.throwIncorrectNumberOfLevels {α : Type} (constName : Name) (us : List Level) :
MetaM α
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def Lean.Meta.throwTypeExcepted {α : Type} (type : Expr) :
MetaM α
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def Lean.Meta.getLevel (type : Expr) :
MetaM Level
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def Lean.Meta.throwUnknownMVar {α : Type} (mvarId : MVarId) :
MetaM α
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@[inline]
def Lean.Meta.withInferTypeConfig {α : Type} (x : MetaM α) :
MetaM α

Ensure MetaM configuration is strong enough for inferring/checking types. For example, beta := true is essential when type checking.

Remark: we previously use the default configuration here, but this is problematic because it overrides unrelated configurations.

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@[export lean_infer_type]
def Lean.Meta.inferTypeImp (e : Expr) :
MetaM Expr
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def Lean.Meta.inferTypeImp.infer (e : Expr) :
MetaM Expr
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partial def Lean.Meta.isPropQuick :
Expr → MetaM LBool

isPropQuick e is an "approximate" predicate which returns LBool.true if e is a proposition.

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def Lean.Meta.isProp (e : Expr) :
MetaM Bool

isProp e returns true if e is a proposition.

If e contains metavariables, it may not be possible to decide whether is a proposition or not. We return false in this case. We considered using LBool and retuning LBool.undef, but we have no applications for it.

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partial def Lean.Meta.isProofQuick :
Expr → MetaM LBool

isProofQuick e is an "approximate" predicate which returns LBool.true if e is a proof.

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def Lean.Meta.isProof (e : Expr) :
MetaM Bool
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partial def Lean.Meta.isTypeQuick :
Expr → MetaM LBool

isTypeQuick e is an "approximate" predicate which returns LBool.true if e is a type.

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def Lean.Meta.isType (e : Expr) :
MetaM Bool

Return true iff the type of e is a Sort _.

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def Lean.Meta.typeFormerTypeLevelQuick :
Expr → Option Level
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def Lean.Meta.typeFormerTypeLevel (type : Expr) :
MetaM (Option Level)

Return u iff type is Sort u or As → Sort u.

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partial def Lean.Meta.typeFormerTypeLevel.go (type : Expr) (xs : Array Expr) :
MetaM (Option Level)
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def Lean.Meta.isTypeFormerType (type : Expr) :
MetaM Bool

Return true iff type is Sort _ or As → Sort _.

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def Lean.Meta.isPropFormerType (type : Expr) :
MetaM Bool

Return true iff type is Prop or As → Prop.

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def Lean.Meta.isTypeFormer (e : Expr) :
MetaM Bool

Return true iff e : Sort _ or e : (forall As, Sort _). Remark: it subsumes isType

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def Lean.Meta.arrowDomainsN (n : Nat) (type : Expr) :
MetaM (Array Expr)

Given n and a non-dependent function type α₁ → α₂ → ... → αₙ → Sort u, returns the types α₁, α₂, ..., αₙ. Throws an error if there are not at least n argument types or if a later argument type depends on a prior one (i.e., it's a dependent function type).

This can be used to infer the expected type of the alternatives when constructing a MatcherApp.

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def Lean.Meta.inferArgumentTypesN (n : Nat) (e : Expr) :
MetaM (Array Expr)

Infers the types of the next n parameters that e expects. See arrowDomainsN.

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