staticcheck: don't flag nil constants as useless assignments

Closes gh-733
dominikh · Jul 30, 2020 · 276c3dd · 276c3dd
1 parent 3c17a0d
commit 276c3dd
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Showing 2 changed files with 16 additions and 0 deletions.
diff --git a/staticcheck/lint.go b/staticcheck/lint.go
@@ -1721,6 +1721,10 @@ func CheckUnreadVariableValues(pass *analysis.Pass) (interface{}, error) {
 					continue
 				}
 
+				if _, ok := val.(*ir.Const); ok {
+					// a zero-valued constant, for example in 'foo := []string(nil)'
+					continue
+				}
 				if !hasUse(val, nil) {
 					report.Report(pass, assign, fmt.Sprintf("this value of %s is never used", lhs))
 				}

diff --git a/staticcheck/testdata/src/CheckUnreadVariableValues/CheckUnreadVariableValues.go b/staticcheck/testdata/src/CheckUnreadVariableValues/CheckUnreadVariableValues.go
@@ -1,5 +1,7 @@
 package pkg
 
+import "fmt"
+
 func fn1() {
 	var x int
 	x = gen() // want `this value of x is never used`
@@ -130,3 +132,13 @@ func resolveWeakTypes(types []int) {
 }
 
 func findRunLimit(int) int { return 0 }
+
+func fn10() {
+	slice := []string(nil)
+	if true {
+		slice = []string{"1", "2"}
+	} else {
+		slice = []string{"3", "4"}
+	}
+	fmt.Println(slice)
+}