44 lines
1.8 KiB
Text
44 lines
1.8 KiB
Text
/-
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Copyright (c) 2020 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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import Lean.Data.Options
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/- Basic support for auto bound implicit local names -/
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namespace Lean.Elab
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register_builtin_option autoBoundImplicitLocal : Bool := {
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defValue := true
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descr := "Unbound local variables in declaration headers become implicit arguments if they are a lower case or greek letter followed by numeric digits. For example, `def f (x : Vector α n) : Vector α n :=` automatically introduces the implicit variables {α n}."
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}
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private def isValidAutoBoundSuffix (s : String) : Bool :=
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s.toSubstring.drop 1 |>.all fun c => c.isDigit || isSubScriptAlnum c || c == '_' || c == '\''
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/-
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Remark: Issue #255 exposed a nasty interaction between macro scopes and auto-bound-implicit names.
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```
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local notation "A" => id x
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theorem test : A = A := sorry
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```
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We used to use `n.eraseMacroScopes` at `isValidAutoBoundImplicitName` and `isValidAutoBoundLevelName`.
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Thus, in the example above, when `A` is expanded, a `x` with a fresh macro scope is created.
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`x`+macros-scope is not in scope and is a valid auto-bound implicit name after macro scopes are erased.
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So, an auto-bound exception would be thrown, and `x`+macro-scope would be added as a new implicit.
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When, we try again, a `x` with a new macro scope is created and this process keeps repeating.
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Therefore, we do consider identifier with macro scopes anymore.
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-/
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def isValidAutoBoundImplicitName (n : Name) : Bool :=
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match n with
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| Name.str Name.anonymous s _ => s.length > 0 && (isGreek s[0] || s[0].isLower) && isValidAutoBoundSuffix s
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| _ => false
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def isValidAutoBoundLevelName (n : Name) : Bool :=
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match n with
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| Name.str Name.anonymous s _ => s.length > 0 && s[0].isLower && isValidAutoBoundSuffix s
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| _ => false
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end Lean.Elab
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