x/tools/gopls: invalid range bug in source.FindParam (reported by telemetry)

[adonovan]

This stack 73LKtQ was reported by telemetry:

	start, end, err := pgf.RangePos(rng)
	if err != nil {
		bug.Reportf("(file=%v).RangePos(%v) failed: %v", pgf.URI, rng, err)
		return info
	}

gopls/bug
golang.org/x/tools/gopls/internal/bug.report:35
golang.org/x/tools/gopls/internal/bug.Reportf:1
golang.org/x/tools/gopls/internal/lsp/source.FindParam:4
golang.org/x/tools/gopls/internal/lsp.canRemoveParameter:1
golang.org/x/tools/gopls/internal/lsp.refactorRewrite:14
golang.org/x/tools/gopls/internal/lsp.(*Server).codeAction:220
golang.org/x/tools/gopls/internal/lsp.(*Server).CodeAction:1
golang.org/x/tools/gopls/internal/lsp/protocol.serverDispatch:142
golang.org/x/tools/gopls/internal/lsp/protocol.ServerHandler.func1:5
golang.org/x/tools/gopls/internal/lsp/lsprpc.handshaker.func1:52
golang.org/x/tools/internal/jsonrpc2.MustReplyHandler.func1:2
golang.org/x/tools/internal/jsonrpc2.AsyncHandler.func1.2:3
runtime.goexit:0

golang.org/x/tools/gopls@v0.14.2 go1.19.8 windows/amd64 (3)

Issue created by golang.org/x/tools/gopls/internal/telemetry/cmd/stacks.

[adonovan]

This indicates that an invalid Range was supplied, and at least one of its start/end positions has a line or column number that is beyond EOF, or, less likely, indicates a position on a line containing a UTF-8 encoding error.

I think the bug.Report is erroneous, and FindParam should return an "invalid position" error.

[gopherbot]

Change https://go.dev/cl/548738 mentions this issue: gopls/internal: don't bug.Report when given an invalid position