--- /dev/null
+// errorcheck
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+import "unsafe"
+
+const C = 1
+
+var x1, x int
+var b bool
+var s string
+var c chan int
+var cp complex128
+var slice []int
+var array [2]int
+var bytes []byte
+var runes []rune
+var r rune
+
+func f0() {}
+func f1() int { return 1 }
+func f2() (int, int) { return 1, 1 }
+
+type T struct{ X int }
+
+func (T) M1() int { return 1 }
+func (T) M0() {}
+func (T) M() {}
+
+var t T
+var tp *T
+
+type I interface{ M() }
+
+var i I
+
+var m map[int]int
+
+func _() {
+ // Note: if the next line changes to x, the error silences the x+x etc below!
+ x1 // ERROR "x1 evaluated but not used"
+
+ nil // ERROR "nil evaluated but not used"
+ C // ERROR "C evaluated but not used"
+ 1 // ERROR "1 evaluated but not used"
+ x + x // ERROR "x \+ x evaluated but not used"
+ x - x // ERROR "x - x evaluated but not used"
+ x | x // ERROR "x \| x evaluated but not used"
+ "a" + s // ERROR ".a. \+ s evaluated but not used"
+ &x // ERROR "&x evaluated but not used"
+ b && b // ERROR "b && b evaluated but not used"
+ append(slice, 1) // ERROR "append\(slice, 1\) evaluated but not used"
+ string(bytes) // ERROR "string\(bytes\) evaluated but not used"
+ string(runes) // ERROR "string\(runes\) evaluated but not used"
+ f0() // ok
+ f1() // ok
+ f2() // ok
+ _ = f0() // ERROR "f0\(\) used as value"
+ _ = f1() // ok
+ _, _ = f2() // ok
+ _ = f2() // ERROR "assignment mismatch: 1 variable but f2 returns 2 values"
+ T.M0 // ERROR "T.M0 evaluated but not used"
+ t.M0 // ERROR "t.M0 evaluated but not used"
+ cap // ERROR "use of builtin cap not in function call"
+ cap(slice) // ERROR "cap\(slice\) evaluated but not used"
+ close(c) // ok
+ _ = close(c) // ERROR "close\(c\) used as value"
+ func() {} // ERROR "func literal evaluated but not used"
+ X{} // ERROR "undefined: X"
+ map[string]int{} // ERROR "map\[string\]int{} evaluated but not used"
+ struct{}{} // ERROR "struct ?{}{} evaluated but not used"
+ [1]int{} // ERROR "\[1\]int{} evaluated but not used"
+ []int{} // ERROR "\[\]int{} evaluated but not used"
+ &struct{}{} // ERROR "&struct ?{}{} evaluated but not used"
+ float32(x) // ERROR "float32\(x\) evaluated but not used"
+ I(t) // ERROR "I\(t\) evaluated but not used"
+ int(x) // ERROR "int\(x\) evaluated but not used"
+ copy(slice, slice) // ok
+ _ = copy(slice, slice) // ok
+ delete(m, 1) // ok
+ _ = delete(m, 1) // ERROR "delete\(m, 1\) used as value"
+ t.X // ERROR "t.X evaluated but not used"
+ tp.X // ERROR "tp.X evaluated but not used"
+ t.M // ERROR "t.M evaluated but not used"
+ I.M // ERROR "I.M evaluated but not used"
+ i.(T) // ERROR "i.\(T\) evaluated but not used"
+ x == x // ERROR "x == x evaluated but not used"
+ x != x // ERROR "x != x evaluated but not used"
+ x != x // ERROR "x != x evaluated but not used"
+ x < x // ERROR "x < x evaluated but not used"
+ x >= x // ERROR "x >= x evaluated but not used"
+ x > x // ERROR "x > x evaluated but not used"
+ *tp // ERROR "\*tp evaluated but not used"
+ slice[0] // ERROR "slice\[0\] evaluated but not used"
+ m[1] // ERROR "m\[1\] evaluated but not used"
+ len(slice) // ERROR "len\(slice\) evaluated but not used"
+ make(chan int) // ERROR "make\(chan int\) evaluated but not used"
+ make(map[int]int) // ERROR "make\(map\[int\]int\) evaluated but not used"
+ make([]int, 1) // ERROR "make\(\[\]int, 1\) evaluated but not used"
+ x * x // ERROR "x \* x evaluated but not used"
+ x / x // ERROR "x / x evaluated but not used"
+ x % x // ERROR "x % x evaluated but not used"
+ x << x // ERROR "x << x evaluated but not used"
+ x >> x // ERROR "x >> x evaluated but not used"
+ x & x // ERROR "x & x evaluated but not used"
+ x &^ x // ERROR "x &\^ x evaluated but not used"
+ new(int) // ERROR "new\(int\) evaluated but not used"
+ !b // ERROR "!b evaluated but not used"
+ ^x // ERROR "\^x evaluated but not used"
+ +x // ERROR "\+x evaluated but not used"
+ -x // ERROR "-x evaluated but not used"
+ b || b // ERROR "b \|\| b evaluated but not used"
+ panic(1) // ok
+ _ = panic(1) // ERROR "panic\(1\) used as value"
+ print(1) // ok
+ _ = print(1) // ERROR "print\(1\) used as value"
+ println(1) // ok
+ _ = println(1) // ERROR "println\(1\) used as value"
+ (x) // ERROR "x evaluated but not used"
+ c <- 1 // ok
+ slice[1:1] // ERROR "slice\[1:1\] evaluated but not used"
+ array[1:1] // ERROR "array\[1:1\] evaluated but not used"
+ s[1:1] // ERROR "s\[1:1\] evaluated but not used"
+ slice[1:1:1] // ERROR "slice\[1:1:1\] evaluated but not used"
+ array[1:1:1] // ERROR "array\[1:1:1\] evaluated but not used"
+ recover() // ok
+ <-c // ok
+ string(r) // ERROR "string\(r\) evaluated but not used"
+ iota // ERROR "undefined: iota"
+ real(cp) // ERROR "real\(cp\) evaluated but not used"
+ imag(cp) // ERROR "imag\(cp\) evaluated but not used"
+ complex(1, 2) // ERROR "complex\(1, 2\) evaluated but not used"
+ unsafe.Alignof(t.X) // ERROR "unsafe.Alignof\(t.X\) evaluated but not used"
+ unsafe.Offsetof(t.X) // ERROR "unsafe.Offsetof\(t.X\) evaluated but not used"
+ unsafe.Sizeof(t) // ERROR "unsafe.Sizeof\(t\) evaluated but not used"
+ _ = new(x) // ERROR "x is not a type"
+ _ = int // ERROR "type int is not an expression"
+}