compiler: allow slicing arrays of a named type

compiler/compiler.go

@@ -2334,7 +2334,7 @@ func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
 		switch typ := expr.X.Type().Underlying().(type) {
 		case *types.Pointer: // pointer to array
 			// slice an array
-			length := typ.Elem().(*types.Array).Len()
+			length := typ.Elem().Underlying().(*types.Array).Len()
 			llvmLen := llvm.ConstInt(c.uintptrType, uint64(length), false)
 			if high.IsNil() {
 				high = llvmLen

testdata/slice.go

@@ -1,5 +1,7 @@
 package main
 
+type MySlice [32]byte
+
 func main() {
 	l := 5
 	foo := []int{1, 2, 4, 5}
@@ -89,6 +91,12 @@ func main() {
 		print(" ", n)
 	}
 	println()
+
+	// Verify the fix in https://github.com/aykevl/tinygo/pull/119
+	var unnamed [32]byte
+	var named MySlice
+	assert(len(unnamed[:]) == 32)
+	assert(len(named[:]) == 32)
 }
 
 func printslice(name string, s []int) {