internal/core/adt: run evaluator tests in parallel

Now that a pesky data race spotted by these has been resolved
in the previous commit, we can safely run these in parallel.

On my laptop, `go test` drops from ~4.9s to ~1.8s,
and `go test -race` drops fro ~29s to ~12s.

CI should see a similar ~2.5x speed-up, given that it has 8 CPUs.
This is especially nice, as the slowest step is `go test -race ./...`,
and it spends most of its time in the adt package.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I105b20fa5bb54c9ce66db938f3288c9f766c6872
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1218152
Reviewed-by: Marcel van Lohuizen <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mvdan

internal/core/adt/eval_test.go

@@ -45,6 +45,7 @@ var (
 
 // TestEvalV2 tests the old implementation of the evaluator.
 func TestEvalV2(t *testing.T) {
+	t.Parallel()
 	test := cuetxtar.TxTarTest{
 		Root: "../../../cue/testdata",
 		Name: "eval",
@@ -59,12 +60,14 @@ func TestEvalV2(t *testing.T) {
 		test.ToDo = nil
 	}
 
-	test.Run(t, func(tc *cuetxtar.Test) {
-		runEvalTest(tc, internal.EvalV2, dbg, exp)
+	test.Run(t, func(t *cuetxtar.Test) {
+		t.Parallel()
+		runEvalTest(t, internal.EvalV2, dbg, exp)
 	})
 }
 
 func TestEvalV3(t *testing.T) {
+	t.Parallel()
 	adt.DebugDeps = true // check unmatched dependencies.
 
 	test := cuetxtar.TxTarTest{
@@ -82,14 +85,13 @@ func TestEvalV3(t *testing.T) {
 		test.ToDo = nil
 	}
 
-	var errorCount int
 	test.Run(t, func(t *cuetxtar.Test) {
-		errorCount += runEvalTest(t, internal.EvalV3, dbg, exp)
+		t.Parallel()
+		runEvalTest(t, internal.EvalV3, dbg, exp)
 	})
-	t.Logf("nodeErrors: %d", errorCount)
 }
 
-func runEvalTest(t *cuetxtar.Test, version internal.EvaluatorVersion, dbg cuedebug.Config, exp cueexperiment.Config) (errorCount int) {
+func runEvalTest(t *cuetxtar.Test, version internal.EvaluatorVersion, dbg cuedebug.Config, exp cueexperiment.Config) (errorCount int64) {
 	exp.KeepValidators = !t.HasTag("simplifyValidators")
 
 	a := t.Instance()