diff --git a/src/cmd/compile/internal/inline/inl.go b/src/cmd/compile/internal/inline/inl.go
index 143fbe9efe..aa194ebab2 100644
--- a/src/cmd/compile/internal/inline/inl.go
+++ b/src/cmd/compile/internal/inline/inl.go
@@ -346,6 +346,13 @@ func (v *hairyVisitor) doNode(n ir.Node) error {
 		v.budget -= v.extraCallCost
 
 	case ir.OPANIC:
+		n := n.(*ir.UnaryExpr)
+		if n.X.Op() == ir.OCONVIFACE && n.X.(*ir.ConvExpr).Implicit() {
+			// Hack to keep reflect.flag.mustBe inlinable for TestIntendedInlining.
+			// Before CL 284412, these conversions were introduced later in the
+			// compiler, so they didn't count against inlining budget.
+			v.budget++
+		}
 		v.budget -= inlineExtraPanicCost
 
 	case ir.ORECOVER:
diff --git a/src/cmd/compile/internal/typecheck/func.go b/src/cmd/compile/internal/typecheck/func.go
index c832d9700f..b576590d4d 100644
--- a/src/cmd/compile/internal/typecheck/func.go
+++ b/src/cmd/compile/internal/typecheck/func.go
@@ -896,7 +896,7 @@ func tcNew(n *ir.UnaryExpr) ir.Node {
 // tcPanic typechecks an OPANIC node.
 func tcPanic(n *ir.UnaryExpr) ir.Node {
 	n.X = Expr(n.X)
-	n.X = DefaultLit(n.X, types.Types[types.TINTER])
+	n.X = AssignConv(n.X, types.Types[types.TINTER], "argument to panic")
 	if n.X.Type() == nil {
 		n.SetType(nil)
 		return n
diff --git a/src/cmd/compile/internal/walk/order.go b/src/cmd/compile/internal/walk/order.go
index e1e9f168bb..fe0b6a0eff 100644
--- a/src/cmd/compile/internal/walk/order.go
+++ b/src/cmd/compile/internal/walk/order.go
@@ -768,14 +768,12 @@ func (o *orderState) stmt(n ir.Node) {
 		orderBlock(&n.Else, o.free)
 		o.out = append(o.out, n)
 
-	// Special: argument will be converted to interface using convT2E
-	// so make sure it is an addressable temporary.
 	case ir.OPANIC:
 		n := n.(*ir.UnaryExpr)
 		t := o.markTemp()
 		n.X = o.expr(n.X, nil)
-		if !n.X.Type().IsInterface() {
-			n.X = o.addrTemp(n.X)
+		if !n.X.Type().IsEmptyInterface() {
+			base.FatalfAt(n.Pos(), "bad argument to panic: %L", n.X)
 		}
 		o.out = append(o.out, n)
 		o.cleanTemp(t)
diff --git a/test/closure3.dir/main.go b/test/closure3.dir/main.go
index 5694673f1e..e8e1e99860 100644
--- a/test/closure3.dir/main.go
+++ b/test/closure3.dir/main.go
@@ -285,5 +285,5 @@ func main() {
 
 //go:noinline
 func ppanic(s string) { // ERROR "leaking param: s"
-	panic(s)
+	panic(s) // ERROR "s escapes to heap"
 }
diff --git a/test/escape2.go b/test/escape2.go
index 5c6eb559fa..b9b723d866 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1547,7 +1547,7 @@ func foo153(v interface{}) *int { // ERROR "v does not escape"
 	case int: // ERROR "moved to heap: x$"
 		return &x
 	}
-	panic(0)
+	panic(0) // ERROR "0 escapes to heap"
 }
 
 // issue 8185 - &result escaping into result
diff --git a/test/escape2n.go b/test/escape2n.go
index 46e58f8566..7c8208aa73 100644
--- a/test/escape2n.go
+++ b/test/escape2n.go
@@ -1547,7 +1547,7 @@ func foo153(v interface{}) *int { // ERROR "v does not escape"
 	case int: // ERROR "moved to heap: x$"
 		return &x
 	}
-	panic(0)
+	panic(0) // ERROR "0 escapes to heap"
 }
 
 // issue 8185 - &result escaping into result
diff --git a/test/escape4.go b/test/escape4.go
index a4a9c14a3e..4e50231bf9 100644
--- a/test/escape4.go
+++ b/test/escape4.go
@@ -35,14 +35,14 @@ func f1() {
 func f2() {} // ERROR "can inline f2"
 
 // No inline for recover; panic now allowed to inline.
-func f3() { panic(1) } // ERROR "can inline f3"
+func f3() { panic(1) } // ERROR "can inline f3" "1 escapes to heap"
 func f4() { recover() }
 
 func f5() *byte {
 	type T struct {
 		x [1]byte
 	}
-	t := new(T)    // ERROR "new.T. escapes to heap"
+	t := new(T) // ERROR "new.T. escapes to heap"
 	return &t.x[0]
 }
 
@@ -52,6 +52,6 @@ func f6() *byte {
 			y byte
 		}
 	}
-	t := new(T)   // ERROR "new.T. escapes to heap"
+	t := new(T) // ERROR "new.T. escapes to heap"
 	return &t.x.y
 }
diff --git a/test/fixedbugs/issue13799.go b/test/fixedbugs/issue13799.go
index fbdd4c32bc..c8ecfc54e4 100644
--- a/test/fixedbugs/issue13799.go
+++ b/test/fixedbugs/issue13799.go
@@ -60,7 +60,7 @@ func test1(iter int) {
 	}
 
 	if len(m) != maxI {
-		panic(fmt.Sprintf("iter %d: maxI = %d, len(m) = %d", iter, maxI, len(m))) // ERROR "iter escapes to heap$" "len\(m\) escapes to heap$" "maxI escapes to heap$" "... argument does not escape$"
+		panic(fmt.Sprintf("iter %d: maxI = %d, len(m) = %d", iter, maxI, len(m))) // ERROR "iter escapes to heap$" "len\(m\) escapes to heap$" "maxI escapes to heap$" "... argument does not escape$" "fmt.Sprintf\(.*\) escapes to heap"
 	}
 }
 
@@ -84,7 +84,7 @@ func test2(iter int) {
 	}
 
 	if len(m) != maxI {
-		panic(fmt.Sprintf("iter %d: maxI = %d, len(m) = %d", iter, maxI, len(m))) // ERROR "iter escapes to heap$" "len\(m\) escapes to heap$" "maxI escapes to heap$" "... argument does not escape$"
+		panic(fmt.Sprintf("iter %d: maxI = %d, len(m) = %d", iter, maxI, len(m))) // ERROR "iter escapes to heap$" "len\(m\) escapes to heap$" "maxI escapes to heap$" "... argument does not escape$" "fmt.Sprintf\(.*\) escapes to heap"
 	}
 }
 
@@ -110,7 +110,7 @@ func test3(iter int) {
 	}
 
 	if *m != maxI {
-		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$"
+		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$" "fmt.Sprintf\(.*\) escapes to heap"
 	}
 }
 
@@ -136,7 +136,7 @@ func test4(iter int) {
 	}
 
 	if *m != maxI {
-		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$"
+		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$" "fmt.Sprintf\(.*\) escapes to heap"
 	}
 }
 
@@ -167,7 +167,7 @@ func test5(iter int) {
 	}
 
 	if *m != maxI {
-		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$"
+		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$" "fmt.Sprintf\(.*\) escapes to heap"
 	}
 }
 
@@ -185,6 +185,6 @@ func test6(iter int) {
 	}
 
 	if *m != maxI {
-		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$"
+		panic(fmt.Sprintf("iter %d: maxI = %d, *m = %d", iter, maxI, *m)) // ERROR "\*m escapes to heap$" "iter escapes to heap$" "maxI escapes to heap$" "... argument does not escape$" "fmt.Sprintf\(.*\) escapes to heap"
 	}
 }
diff --git a/test/fixedbugs/issue7921.go b/test/fixedbugs/issue7921.go
index a4e7b246d4..65be4b5bbe 100644
--- a/test/fixedbugs/issue7921.go
+++ b/test/fixedbugs/issue7921.go
@@ -41,7 +41,7 @@ func bufferNoEscape3(xs []string) string { // ERROR "xs does not escape$"
 
 func bufferNoEscape4() []byte {
 	var b bytes.Buffer
-	b.Grow(64) // ERROR "bufferNoEscape4 ignoring self-assignment in bytes.b.buf = bytes.b.buf\[:bytes.m\]$" "inlining call to bytes.\(\*Buffer\).Grow$"
+	b.Grow(64) // ERROR "bufferNoEscape4 ignoring self-assignment in bytes.b.buf = bytes.b.buf\[:bytes.m\]$" "inlining call to bytes.\(\*Buffer\).Grow$" "string\(.*\) escapes to heap"
 	useBuffer(&b)
 	return b.Bytes() // ERROR "inlining call to bytes.\(\*Buffer\).Bytes$"
 }