cmd/compile: allow inlining of functions with switch statements

Allow inlining of functions with switch statements as long as they don't
contain a break or type switch.

Fixes #13071

Change-Id: I057be351ea4584def1a744ee87eafa5df47a7f6d
Reviewed-on: https://go-review.googlesource.com/20824Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/fmt.go

@@ -888,7 +888,7 @@ func stmtfmt(n *Node) string {
 			f += fmt.Sprintf(" %v;", n.Ninit.First())
 		}
 		if n.Left != nil {
-			f += Nconv(n.Left, 0)
+			f += fmt.Sprintf(" %s ", Nconv(n.Left, 0))
 		}
 
 		f += fmt.Sprintf(" { %v }", n.List)

src/cmd/compile/internal/gc/inl.go

@@ -214,10 +214,11 @@ func ishairy(n *Node, budget *int) bool {
 		ORANGE,
 		OFOR,
 		OSELECT,
-		OSWITCH,
+		OTYPESW,
 		OPROC,
 		ODEFER,
 		ODCLTYPE, // can't print yet
+		OBREAK,
 		ORETJMP:
 		return true
 	}

test/inline.go

@@ -36,3 +36,39 @@ func i(x int) int { // ERROR "can inline i"
 	const y = 2
 	return x + y
 }
+
+func j(x int) int { // ERROR "can inline j"
+	switch {
+	case x > 0:
+		return x + 2
+	default:
+		return x + 1
+	}
+}
+
+// can't currently inline functions with a break statement
+func switchBreak(x, y int) int {
+	var n int
+	switch x {
+	case 0:
+		n = 1
+	Done:
+		switch y {
+		case 0:
+			n += 10
+			break Done
+		}
+		n = 2
+	}
+	return n
+}
+
+// can't currently inline functions with a type switch
+func switchType(x interface{}) int { // ERROR "switchType x does not escape"
+	switch x.(type) {
+	case int:
+		return x.(int)
+	default:
+		return 0
+	}
+}