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go/types, types2: provide better error message for short variable declarations #43087

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griesemer opened this issue Dec 9, 2020 · 3 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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@griesemer
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Given

var a int
a, b, b := 1, 2, 3
_ = a
_ = b

The compiler reports: b repeated on left side of :=.
types2 (go tool compile -G) reports: b redeclared in this block.

The compiler error message seems better because it's actually ok to "redeclare" a variable (here: a) with a short variable declaration.

cc: @findleyr

@griesemer griesemer added the NeedsFix The path to resolution is known, but the work has not been done. label Dec 9, 2020
@griesemer griesemer added this to the Go1.17 milestone Dec 9, 2020
@griesemer griesemer self-assigned this Dec 9, 2020
@griesemer griesemer changed the title types2: provide better error message for short variable errors types2: provide better error message for short variable declarations Dec 9, 2020
@griesemer griesemer changed the title types2: provide better error message for short variable declarations go/types, types2: provide better error message for short variable declarations Apr 21, 2021
@gopherbot
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Change https://golang.org/cl/312170 mentions this issue: cmd/compile/internal/types2: better errors for invalid short var decls

@griesemer
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cc: @findleyr

gopherbot pushed a commit that referenced this issue Apr 22, 2021
- rewrite Checker.shortVarDecl core loop for clarity
- match compiler error messages (#43087)
- don't allow multiple identical redeclarations (#45652)

For #43087.
For #45652.

Change-Id: I8c3329a553aa104d7853fbaea8b88049bc9b3b88
Reviewed-on: https://go-review.googlesource.com/c/go/+/312170
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
@griesemer griesemer modified the milestones: Go1.17, Go1.18 Apr 28, 2021
@findleyr
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This was resolved by the port to go/types: https://golang.org/cl/314629.

@golang golang locked and limited conversation to collaborators Apr 29, 2022
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