gopls/internal/golang: don't suggest removeparam when there are errors

Update the canRemoveParameter logic to reflect that we don't try to
remove parameters when there are parse or type errors.

Change-Id: Ia8239a383b56763d100c69c9a3633c87025b81cf
Reviewed-on: https://go-review.googlesource.com/c/tools/+/572297
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: findleyr

gopls/internal/golang/change_signature.go

@@ -45,6 +45,9 @@ func RemoveUnusedParameter(ctx context.Context, fh file.Handle, rng protocol.Ran
 	if err != nil {
 		return nil, err
 	}
+
+	// Changes to our heuristics for whether we can remove a parameter must also
+	// be reflected in the canRemoveParameter helper.
 	if perrors, terrors := pkg.ParseErrors(), pkg.TypeErrors(); len(perrors) > 0 || len(terrors) > 0 {
 		var sample string
 		if len(perrors) > 0 {

gopls/internal/golang/codeaction.go

@@ -401,12 +401,16 @@ func getRewriteCodeActions(ctx context.Context, pkg *cache.Package, snapshot *ca
 // indicated by the given [start, end) range.
 //
 // This is true if:
+//   - there are no parse or type errors, and
 //   - [start, end) is contained within an unused field or parameter name
 //   - ... of a non-method function declaration.
 //
 // (Note that the unusedparam analyzer also computes this property, but
 // much more precisely, allowing it to report its findings as diagnostics.)
 func canRemoveParameter(pkg *cache.Package, pgf *parsego.File, rng protocol.Range) bool {
+	if perrors, terrors := pkg.ParseErrors(), pkg.TypeErrors(); len(perrors) > 0 || len(terrors) > 0 {
+		return false // can't remove parameters from packages with errors
+	}
 	info, err := FindParam(pgf, rng)
 	if err != nil {
 		return false // e.g. invalid range
@@ -449,7 +453,7 @@ func getInlineCodeActions(pkg *cache.Package, pgf *parsego.File, rng protocol.Ra
 		return nil, err
 	}
 
-	// If range is within call expression, offer inline action.
+	// If range is within call expression, offer to inline the call.
 	var commands []protocol.Command
 	if _, fn, err := EnclosingStaticCall(pkg, pgf, start, end); err == nil {
 		cmd, err := command.NewApplyFixCommand(fmt.Sprintf("Inline call to %s", fn.Name()), command.ApplyFixArgs{

gopls/internal/test/marker/testdata/codeaction/removeparam_witherrs.txt

@@ -0,0 +1,11 @@
+This test checks that we can't remove parameters for packages with errors.
+
+-- p.go --
+package p
+
+func foo(unused int) { //@codeactionerr("unused", "unused", "refactor.rewrite", re"found 0")
+}
+
+func _() {
+	foo("") //@diag(`""`, re"cannot use")
+}