ambiguous identifier resolution #23123
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Araq
reviewed
Dec 27, 2023
Araq
reviewed
Dec 27, 2023
compiler/semexprs.nim
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| @@ -2997,6 +2998,53 @@ proc semPragmaStmt(c: PContext; n: PNode) = | |||
| else: | |||
| pragma(c, c.p.owner, n, stmtPragmas, true) | |||
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| proc resolveIdent(c: PContext, ident: PIdent, s: var PSym, n: PNode, | |||
| flags: TExprFlags, expectedType: PType): PNode = | |||
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So ... it returns what exactly? And when does it overwrite the s parameter? Convoluted.
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I swapped s and the result value, and made it so only n's info is needed. Every parameter seems to be needed though, not sure how to get this cleaner.
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Now merged n/info and ident into the same parameter (just n), and renamed to resolveIdentToSym. Hopefully this is clearer.
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I'm merging this now but in a followup PR the manual needs to be patched and describe in detail how symbol lookups now interact with overloading etc. |
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Thanks for your hard work on this PR! Hint: mm: orc; opt: speed; options: -d:release |
metagn
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TODO: followup needed
Araq
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refs #23123 Not sure if detailed enough.
Araq
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refs #23586 (comment) In #20091 a bad kind of type inference was mistakenly left in where if an identifier `abc` had an expected type of an enum type `Enum`, and `Enum` had a member called `abc`, the identifier would change to be that enum member. This causes bugs where a local symbol can have the same name as an enum member but have a different value. I had assumed this behavior was removed since but it wasn't, and CI seems to pass having it removed. A separate PR needs to be made for the 2.0 branch because these lines were moved around during a refactoring in #23123 which is not in 2.0.
narimiran
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fixes #23002, fixes #22841, refs comments in #23097 When an identifier is ambiguous in scope (i.e. multiple imports contain symbols with the same name), attempt resolving it through type inference (by creating a symchoice). To do this efficiently, `qualifiedLookUp` had to be broken up so that `semExpr` can access the ambiguous candidates directly (now obtained directly via `lookUpCandidates`). This fixes the linked issues, but an example like: ```nim let on = 123 {.warning[ProveInit]: on.} ``` will still fail, since `on` is unambiguously the local `let` symbol here (this is also true for `proc on` but `proc` symbols generate symchoices anyway). Type symbols are not considered to not confuse the type inference. This includes the change in sigmatch, up to this point symchoices with nonoverloadable symbols could be created, they just wouldn't be considered during disambiguation. Now every proper symbol except types are considered in disambiguation, so the correct symbols must be picked during the creation of the symchoice node. I remember there being a violating case of this in the compiler, but this was very likely fixed by excluding type symbols as CI seems to have found no issues. The pure enum ambiguity test was disabled because ambiguous pure enums now behave like overloadable enums with this behavior, so we get a longer error message for `echo amb` like `type mismatch: got <MyEnum | OtherEnum> but expected T` (cherry picked from commit b280100)
narimiran
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fixes #23002, fixes #22841, refs comments in #23097 When an identifier is ambiguous in scope (i.e. multiple imports contain symbols with the same name), attempt resolving it through type inference (by creating a symchoice). To do this efficiently, `qualifiedLookUp` had to be broken up so that `semExpr` can access the ambiguous candidates directly (now obtained directly via `lookUpCandidates`). This fixes the linked issues, but an example like: ```nim let on = 123 {.warning[ProveInit]: on.} ``` will still fail, since `on` is unambiguously the local `let` symbol here (this is also true for `proc on` but `proc` symbols generate symchoices anyway). Type symbols are not considered to not confuse the type inference. This includes the change in sigmatch, up to this point symchoices with nonoverloadable symbols could be created, they just wouldn't be considered during disambiguation. Now every proper symbol except types are considered in disambiguation, so the correct symbols must be picked during the creation of the symchoice node. I remember there being a violating case of this in the compiler, but this was very likely fixed by excluding type symbols as CI seems to have found no issues. The pure enum ambiguity test was disabled because ambiguous pure enums now behave like overloadable enums with this behavior, so we get a longer error message for `echo amb` like `type mismatch: got <MyEnum | OtherEnum> but expected T` (cherry picked from commit b280100)
narimiran
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refs #23586 (comment) In #20091 a bad kind of type inference was mistakenly left in where if an identifier `abc` had an expected type of an enum type `Enum`, and `Enum` had a member called `abc`, the identifier would change to be that enum member. This causes bugs where a local symbol can have the same name as an enum member but have a different value. I had assumed this behavior was removed since but it wasn't, and CI seems to pass having it removed. A separate PR needs to be made for the 2.0 branch because these lines were moved around during a refactoring in #23123 which is not in 2.0. (cherry picked from commit c101490)
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fixes #23002, fixes #22841, refs comments in #23097
When an identifier is ambiguous in scope (i.e. multiple imports contain symbols with the same name), attempt resolving it through type inference (by creating a symchoice). To do this efficiently,
qualifiedLookUphad to be broken up so thatsemExprcan access the ambiguous candidates directly (now obtained directly vialookUpCandidates).This fixes the linked issues, but an example like:
will still fail, since
onis unambiguously the localletsymbol here (this is also true forproc onbutprocsymbols generate symchoices anyway).Type symbols are not considered to not confuse the type inference. This includes the change in sigmatch, up to this point symchoices with nonoverloadable symbols could be created, they just wouldn't be considered during disambiguation. Now every proper symbol except types are considered in disambiguation, so the correct symbols must be picked during the creation of the symchoice node. I remember there being a violating case of this in the compiler, but this was very likely fixed by excluding type symbols as CI seems to have found no issues.
The pure enum ambiguity test was disabled because ambiguous pure enums now behave like overloadable enums with this behavior, so we get a longer error message for
echo ambliketype mismatch: got <MyEnum | OtherEnum> but expected T