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x/tools/gopls: panic in deslice when completing unknown type in append #38091

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chlunde opened this issue Mar 26, 2020 · 2 comments
Closed

x/tools/gopls: panic in deslice when completing unknown type in append #38091

chlunde opened this issue Mar 26, 2020 · 2 comments
Labels
FrozenDueToAge gopls Issues related to the Go language server, gopls. NeedsFix The path to resolution is known, but the work has not been done. Tools This label describes issues relating to any tools in the x/tools repository.
Milestone
gopls/v0.4.0

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@chlunde
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chlunde commented Mar 26, 2020

What did you do?

Type t in struct in an append variadic arg for a slice with a type now yet defined.

package bad

func _() {
       a := unknown
       a = append(a, struct) //@complete(")")
}

What did you expect to see?

Not much

What did you see instead?

Crash

Stack trace
panic: runtime error: invalid memory address or nil pointer dereference                                                                                                                                                                        
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x79e7db]                                                                                                                                                                        

goroutine 10025 [running]:

golang.org/x/tools/internal/lsp/source.deslice(...)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/source/util.go:429

golang.org/x/tools/internal/lsp/source.(*completer).builtinArgType(0xc0086f0600, 0xe25040, 0xc000100cd0, 0xc0071bc240, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/source/completion_builtin.go:70 +0x3bb

golang.org/x/tools/internal/lsp/source.expectedCandidate.func1(0xc0086f0600, 0xe25040, 0xc000100cd0, 0xc0071bc240, 0xc01032c160)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/source/completion.go:1481 +0xd1

golang.org/x/tools/internal/lsp/source.expectedCandidate(0xc0086f0600, 0xc00025b4b0, 0xc010ae66c0, 0xc0000c5300, 0x116f, 0x1300, 0xb9e2e2, 0x52, 0xc0101eb990, 0x6, ...)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/source/completion.go:1565 +0x3c7

golang.org/x/tools/internal/lsp/source.Completion(0xe12e60, 0xc010ae66c0, 0xe24f00, 0xc012cc2120, 0xe11560, 0xc012cc20c0, 0x4065a00000000000, 0x4045000000000000, 0x0, 0x0, ...)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/source/completion.go:517 +0x9eb

golang.org/x/tools/internal/lsp.(*Server).completion(0xc0002e6680, 0xe12e60, 0xc010b00450, 0xc010536060, 0x0, 0x0, 0xc01032c000)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/completion.go:27 +0x6b0

golang.org/x/tools/internal/lsp.(*Server).Completion(0xc0002e6680, 0xe12e60, 0xc010b00450, 0xc010536060, 0xc010536060, 0x0, 0x0)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/server_gen.go:24 +0x49

golang.org/x/tools/internal/lsp/protocol.serverHandler.Deliver(0xe2d340, 0xc0002e6680, 0xe12e60, 0xc010b00450, 0xc010a7e1c0, 0xae8c00, 0xe10000)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/lsp/protocol/tsserver.go:345 +0x2064

golang.org/x/tools/internal/jsonrpc2.(*Conn).Run.func1(0xc0075ec4e0, 0xc010a7e1c0, 0xc0002eaba0, 0xe12e60, 0xc010b00450, 0x0, 0x0, 0xc0071500f0)

/home/chlunde/opt/gotoolpath/pkg/mod/golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a/internal/jsonrpc2/jsonrpc2.go:372 +0x160

created by golang.org/x/tools/internal/jsonrpc2.(*Conn).Run

Build info

gopls v0.3.4
golang.org/x/tools/gopls v0.3.4
    golang.org/x/tools/gopls@v0.3.4 h1:4GC7q/pXQ/tsxHBGVdsMdlB4gCxVC06m/7rIXg1Px4E=
    github.com/BurntSushi/toml@v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
    github.com/sergi/go-diff@v1.0.0 h1:Kpca3qRNrduNnOQeazBd0ysaKrUJiIuISHxogkT9RPQ=
    golang.org/x/mod@v0.1.1-0.20191105210325-c90efee705ee h1:WG0RUwxtNT4qqaXX3DPA8zHFNm/D9xaBpxzHt1WcA/E=
    golang.org/x/sync@v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
    golang.org/x/tools@v0.0.0-20200316194252-fafb6e2e8a4a h1:hKrQy/q8/Xivoqgw6nGiz1jqpn1WGBLDcWLZwW0983E=
    golang.org/x/xerrors@v0.0.0-20191011141410-1b5146add898 h1:/atklqdjdhuosWIl6AIbOeHJjicWYPqR9bpxqxYG2pA=
    honnef.co/go/tools@v0.0.1-2020.1.3 h1:sXmLre5bzIR6ypkjXCDI3jHPssRhc8KD/Ome589sc3U=
    mvdan.cc/xurls/v2@v2.1.0 h1:KaMb5GLhlcSX+e+qhbRJODnUUBvlw01jt4yrjFIHAuA=

Hack/patch

Not sure if this is the right approach ¯\(ツ)/¯

diff --git a/internal/lsp/testdata/lsp/primarymod/bad/bad2.go b/internal/lsp/testdata/lsp/primarymod/bad/bad2.go
new file mode 100644
index 00000000..acce3e45
--- /dev/null
+++ b/internal/lsp/testdata/lsp/primarymod/bad/bad2.go
@@ -0,0 +1,6 @@
+package bad
+
+func _() {
+       a := unknown
+       a = append(a, struct) //@complete(")")
+}
diff --git a/internal/lsp/testdata/lsp/summary.txt.golden b/internal/lsp/testdata/lsp/summary.txt.golden
index c4e7d68d..ece318e5 100644
--- a/internal/lsp/testdata/lsp/summary.txt.golden
+++ b/internal/lsp/testdata/lsp/summary.txt.golden
@@ -1,6 +1,6 @@
 -- summary --
 CodeLensCount = 2
-CompletionsCount = 237
+CompletionsCount = 238
 CompletionSnippetCount = 75
 UnimportedCompletionsCount = 11
 DeepCompletionsCount = 5
diff --git a/internal/lsp/source/completion_builtin.go b/internal/lsp/source/completion_builtin.go
index d65eb8f4..26c553f0 100644
--- a/internal/lsp/source/completion_builtin.go
+++ b/internal/lsp/source/completion_builtin.go
@@ -64,7 +64,7 @@ func (c *completer) builtinArgType(obj types.Object, call *ast.CallExpr, parentI
                // Check if we are completing the variadic append() param.
                if exprIdx == 1 && len(call.Args) <= 2 {
                        inf.variadicType = deslice(inf.objType)
-               } else if exprIdx > 0 {
+               } else if exprIdx > 0 && inf.objType != nil {
                        // If we are completing an individual element of the variadic
                        // param, "deslice" the expected type.
                        inf.objType = deslice(inf.objType)
@gopherbot gopherbot added this to the Unreleased milestone Mar 26, 2020
@gopherbot gopherbot added Tools This label describes issues relating to any tools in the x/tools repository. gopls Issues related to the Go language server, gopls. labels Mar 26, 2020
@stamblerre
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Thanks for the report! The patch you proposed above sounds reasonable to me - please send us a PR if you're interested in contributing :)

/cc @muirdm

@gopherbot
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Change https://golang.org/cl/227026 mentions this issue: internal/lsp: fix panic in builtin completions

@stamblerre stamblerre added the NeedsFix The path to resolution is known, but the work has not been done. label Apr 2, 2020
@golang golang locked and limited conversation to collaborators Apr 2, 2021
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FrozenDueToAge gopls Issues related to the Go language server, gopls. NeedsFix The path to resolution is known, but the work has not been done. Tools This label describes issues relating to any tools in the x/tools repository.
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