go/packages: report type errors unconditionally

Ensure that when types.Checker.Files returns an error some
error is always reported and the package is illTyped.

Adds an additional hint to recompile the tool when types returns
an error "package requires newer Go version 1.22" or similar.

Updates golang/go#65608
Updates golang/go#66525

Change-Id: I131ee3e668815f88d16a18c6e92f002220284a03
Reviewed-on: https://go-review.googlesource.com/c/tools/+/574255
Reviewed-by: Zvonimir Pavlinovic <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: timothy-king

go/packages/packages.go

@@ -1129,10 +1129,24 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 			return
 		}
 	}
-	types.NewChecker(tc, ld.Fset, lpkg.Types, lpkg.TypesInfo).Files(lpkg.Syntax)
 
+	typErr := types.NewChecker(tc, ld.Fset, lpkg.Types, lpkg.TypesInfo).Files(lpkg.Syntax)
 	lpkg.importErrors = nil // no longer needed
 
+	// In go/types go1.21 and go1.22, Checker.Files failed fast with a
+	// a "too new" error, without calling tc.Error and without
+	// proceeding to type-check the package (#66525).
+	// We rely on the runtimeVersion error to give the suggested remedy.
+	if typErr != nil && len(lpkg.Errors) == 0 && len(lpkg.Syntax) > 0 {
+		if msg := typErr.Error(); strings.HasPrefix(msg, "package requires newer Go version") {
+			appendError(types.Error{
+				Fset: ld.Fset,
+				Pos:  lpkg.Syntax[0].Package,
+				Msg:  msg,
+			})
+		}
+	}
+
 	// If !Cgo, the type-checker uses FakeImportC mode, so
 	// it doesn't invoke the importer for import "C",
 	// nor report an error for the import,
@@ -1154,6 +1168,12 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 		}
 	}
 
+	// If types.Checker.Files had an error that was unreported,
+	// make sure to report the unknown error so the package is illTyped.
+	if typErr != nil && len(lpkg.Errors) == 0 {
+		appendError(typErr)
+	}
+
 	// Record accumulated errors.
 	illTyped := len(lpkg.Errors) > 0
 	if !illTyped {