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cmd/compile: improve error message for invalid use of interface with type constraints #50837

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virtuald opened this issue Jan 26, 2022 · 3 comments
Closed

cmd/compile: improve error message for invalid use of interface with type constraints #50837

virtuald opened this issue Jan 26, 2022 · 3 comments
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@griesemer
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FrozenDueToAge help wanted NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.19

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@virtuald
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What did you do?

https://gotipplay.golang.org/p/K_OPRyt5aJo

package main

type C interface {
	~int
	Fn()
}

func UseInterface(c C) {}

type Foo struct {
	I C
}

What did you expect to see?

./prog.go:8:21: interface with type constraints used as function parameter
./prog.go:11:4: interface with type constraints cannot be used as field

What did you see instead?

./prog.go:8:21: interface contains type constraints
./prog.go:11:4: interface contains type constraints
@ianlancetaylor ianlancetaylor changed the title compiler?: Improve interface with type constraint compilation error cmd/compile: improve error message for invalid use of interface with type constraints Jan 26, 2022
@ianlancetaylor ianlancetaylor added help wanted NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jan 26, 2022
@ianlancetaylor ianlancetaylor added this to the Go1.19 milestone Jan 26, 2022
@ianlancetaylor
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CC @griesemer

@griesemer griesemer added NeedsFix The path to resolution is known, but the work has not been done. and removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jan 27, 2022
@griesemer
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griesemer commented Jan 27, 2022 •
edited

The checker.varType function needs a context string so that it can report a context-aware error. Straight-forward to fix, needs some Fingerspitzengefühl for good error messages.

@griesemer griesemer self-assigned this Jan 27, 2022
@griesemer
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This reports now:

./prog.go:8:21: cannot use type C outside a type constraint: interface contains type constraints
./prog.go:11:4: cannot use type C outside a type constraint: interface contains type constraints

not great, but a bit clearer. Closing this for now.

@golang golang locked and limited conversation to collaborators Jun 23, 2023
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@griesemer griesemer

Labels
FrozenDueToAge help wanted NeedsFix The path to resolution is known, but the work has not been done.
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Status: Done
Milestone
Go1.19
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4 participants
@virtuald @ianlancetaylor @griesemer @gopherbot