gopls/internal/analysis/gofix: allow literal array lengths

An array type can be inlined if its length is a literal integer.

For golang/go#32816.

Change-Id: I80c7f18721c813a0ea7039411ddf8a804b5bf0b5
Reviewed-on: https://go-review.googlesource.com/c/tools/+/651655
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: jba

gopls/internal/analysis/gofix/gofix.go

@@ -148,9 +148,12 @@ func (a *analyzer) findAlias(spec *ast.TypeSpec, declInline bool) {
 	//    type A = [N]int
 	//
 	// would result in [5]int, breaking the connection with N.
-	// TODO(jba): accept type expressions where the array size is a literal integer
 	for n := range ast.Preorder(spec.Type) {
 		if ar, ok := n.(*ast.ArrayType); ok && ar.Len != nil {
+			// Make an exception when the array length is a literal int.
+			if lit, ok := ast.Unparen(ar.Len).(*ast.BasicLit); ok && lit.Kind == token.INT {
+				continue
+			}
 			a.pass.Reportf(spec.Pos(), "invalid //go:fix inline directive: array types not supported")
 			return
 		}

gopls/internal/analysis/gofix/testdata/src/a/a.go

@@ -129,6 +129,13 @@ type E = map[[Uno]string][]*T // want `invalid //go:fix inline directive: array
 
 var _ E // nothing should happen here
 
+// literal array lengths are OK
+//
+//go:fix inline
+type EL = map[[2]string][]*T // want EL: `goFixInline alias`
+
+var _ EL // want `Type alias EL should be inlined`
+
 //go:fix inline
 type F = map[internal.T]T // want F: `goFixInline alias`
 

gopls/internal/analysis/gofix/testdata/src/a/a.go.golden

@@ -129,6 +129,13 @@ type E = map[[Uno]string][]*T // want `invalid //go:fix inline directive: array
 
 var _ E // nothing should happen here
 
+// literal array lengths are OK
+//
+//go:fix inline
+type EL = map[[2]string][]*T // want EL: `goFixInline alias`
+
+var _ map[[2]string][]*T // want `Type alias EL should be inlined`
+
 //go:fix inline
 type F = map[internal.T]T // want F: `goFixInline alias`