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Improve error message when instantiating generics with object constructor (#20358)

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* Improve error message when instantiating generics with object constructor

* follow suggestion

* Update compiler/semobjconstr.nim

Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>

* Update tests/errmsgs/t19882_2.nim

Co-authored-by: Clay Sweetser <Varriount@users.noreply.github.com>
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Bung 2022-09-22 09:11:39 +08:00 • committed by GitHub
commit 2afce84616
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2 changed files with 11 additions and 2 deletions
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8
compiler/semobjconstr.nim
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@ -398,8 +398,12 @@ proc semObjConstr(c: PContext, n: PNode, flags: TExprFlags; expectedType: PType
# multiple times as long as they don't have closures. # multiple times as long as they don't have closures.
result.typ.flags.incl tfHasOwned result.typ.flags.incl tfHasOwned
if t.kind != tyObject: if t.kind != tyObject:
return localErrorNode(c, result, return localErrorNode(c, result, if t.kind != tyGenericBody:
"object constructor needs an object type".dup(addDeclaredLoc(c.config, t))) "object constructor needs an object type".dup(addDeclaredLoc(c.config, t))
else: "cannot instantiate: '" &
typeToString(t, preferDesc) &
"'; the object's generic parameters cannot be inferred and must be explicitly given"
)
# Check if the object is fully initialized by recursively testing each # Check if the object is fully initialized by recursively testing each
# field (if this is a case object, initialized fields in two different # field (if this is a case object, initialized fields in two different

5
tests/errmsgs/t19882_2.nim Normal file
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@ -0,0 +1,5 @@
discard """
errormsg: "cannot instantiate: 'A[T]'; the object's generic parameters cannot be inferred and must be explicitly given"
"""
type A[T] = object
var a = A()