lintcmd: print TOML error on invalid config

Previously the error message would get lost:

    % staticcheck
    staticcheck.conf:5:0:  (last key parsed: "dot_import_whitelist") (compile)

This is actually my bug; the ParseError.Message wasn't always set; fixed
with: BurntSushi/toml#411

Now it prints the expected:

    % staticcheck
    staticcheck.conf:2:32: expected a comma (',') or array terminator (']'), but got end of file (last key parsed: "checks") (config)

Closes: gh-1547 [via git-merge-pr]

go.mod

@@ -3,7 +3,7 @@ module honnef.co/go/tools
 go 1.22
 
 require (
-	github.com/BurntSushi/toml v1.3.2
+	github.com/BurntSushi/toml v1.4.1-0.20240526193622-a339e1f7089c
 	golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa
 	golang.org/x/exp/typeparams v0.0.0-20231108232855-2478ac86f678
 	golang.org/x/sys v0.20.0

go.sum

@@ -1,5 +1,5 @@
-github.com/BurntSushi/toml v1.3.2 h1:o7IhLm0Msx3BaB+n3Ag7L8EVlByGnpq14C4YWiu/gL8=
-github.com/BurntSushi/toml v1.3.2/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
+github.com/BurntSushi/toml v1.4.1-0.20240526193622-a339e1f7089c h1:pxW6RcqyfI9/kWtOwnv/G+AzdKuy2ZrqINhenH4HyNs=
+github.com/BurntSushi/toml v1.4.1-0.20240526193622-a339e1f7089c/go.mod h1:ukJfTF/6rtPPRCnwkur4qwRxa8vTRFBF0uk2lLoLwho=
 golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa h1:FRnLl4eNAQl8hwxVVC17teOw8kdjVDVAiFMtgUdTSRQ=
 golang.org/x/exp v0.0.0-20231110203233-9a3e6036ecaa/go.mod h1:zk2irFbV9DP96SEBUUAy67IdHUaZuSnrz1n472HUCLE=
 golang.org/x/exp/typeparams v0.0.0-20231108232855-2478ac86f678 h1:1P7xPZEwZMoBoz0Yze5Nx2/4pxj6nw9ZqHWXqP0iRgQ=

go/loader/loader.go

@@ -336,7 +336,7 @@ func convertError(err error) []packages.Error {
 
 	case config.ParseError:
 		errs = append(errs, packages.Error{
-			Pos:  fmt.Sprintf("%s:%d", err.Filename, err.Position.Line),
+			Pos:  fmt.Sprintf("%s:%d:%d", err.Filename, err.Position.Line, err.Position.Col),
 			Msg:  fmt.Sprintf("%s (last key parsed: %q)", err.Message, err.LastKey),
 			Kind: packages.ParseError,
 		})

lintcmd/lint.go

@@ -429,6 +429,11 @@ func failed(res runner.Result) []diagnostic {
 				msg = msg[1:]
 			}
 
+			cat := "compile"
+			if e.Kind == packages.ParseError {
+				cat = "config"
+			}
+
 			var posn token.Position
 			if e.Pos == "" {
 				// Under certain conditions (malformed package
@@ -456,7 +461,7 @@ func failed(res runner.Result) []diagnostic {
 				Diagnostic: runner.Diagnostic{
 					Position: posn,
 					Message:  msg,
-					Category: "compile",
+					Category: cat,
 				},
 				Severity: severityError,
 			}