S1019: make(map[T]T) and make(map[T]T, 0) are not the same

Closes gh-1070

(cherry picked from commit db46980)

Author: dominikh

simple/doc.go

@@ -248,8 +248,7 @@ After:
 	"S1019": {
 		Title: "Simplify `make` call by omitting redundant arguments",
 		Text: `The \'make\' function has default values for the length and capacity
-arguments. For channels and maps, the length defaults to zero.
-Additionally, for slices the capacity defaults to the length.`,
+arguments. For channels, the length defaults to zero, and for slices, the capacity defaults to the length.`,
 		Since: "2017.1",
 	},
 

simple/lint.go

@@ -1174,7 +1174,8 @@ func CheckMakeLenCap(pass *analysis.Pass) (interface{}, error) {
 		if m, ok := code.Match(pass, checkMakeLenCapQ1, node); ok {
 			T := m.State["typ"].(ast.Expr)
 			size := m.State["size"].(ast.Node)
-			if _, ok := pass.TypesInfo.TypeOf(T).Underlying().(*types.Slice); ok {
+			switch pass.TypesInfo.TypeOf(T).Underlying().(type) {
+			case *types.Slice, *types.Map:
 				return
 			}
 			report.Report(pass, size, fmt.Sprintf("should use make(%s) instead", report.Render(pass, T)), report.FilterGenerated())

simple/testdata/src/CheckMakeLenCap/LintMakeLenCap.go

@@ -6,14 +6,14 @@ func fn() {
 	type s []int
 	type ch chan int
 	_ = make([]int, 1)
-	_ = make([]int, 0)       // length is mandatory for slices, don't suggest removal
-	_ = make(s, 0)           // length is mandatory for slices, don't suggest removal
-	_ = make(chan int, c)    // constant of 0 may be due to debugging, math or platform-specific code
-	_ = make(chan int, 0)    // want `should use make\(chan int\) instead`
-	_ = make(ch, 0)          // want `should use make\(ch\) instead`
-	_ = make(map[int]int, 0) // want `should use make\(map\[int\]int\) instead`
-	_ = make([]int, 1, 1)    // want `should use make\(\[\]int, 1\) instead`
-	_ = make([]int, x, x)    // want `should use make\(\[\]int, x\) instead`
+	_ = make([]int, 0)    // length is mandatory for slices, don't suggest removal
+	_ = make(s, 0)        // length is mandatory for slices, don't suggest removal
+	_ = make(chan int, c) // constant of 0 may be due to debugging, math or platform-specific code
+	_ = make(chan int, 0) // want `should use make\(chan int\) instead`
+	_ = make(ch, 0)       // want `should use make\(ch\) instead`
+	_ = make(map[int]int, 0)
+	_ = make([]int, 1, 1) // want `should use make\(\[\]int, 1\) instead`
+	_ = make([]int, x, x) // want `should use make\(\[\]int, x\) instead`
 	_ = make([]int, 1, 2)
 	_ = make([]int, x, y)
 }