JS: don't merge let/const declarations with for/while, fixes #325

Author: tdewolff

js/js_test.go

@@ -551,8 +551,10 @@ func TestJS(t *testing.T) {
 		{`a in 5;for(;b;)c()`, `for((a in 5);b;)c()`}, // is longer
 		{`a in 5;for(b=4;b;)c()`, `a in 5;for(b=4;b;)c()`},
 		{`var a=5;for(;b;)c()`, `for(var a=5;b;)c()`},
+		{`let a=5;for(;b;)c()`, `let a=5;for(;b;)c()`},
 		{`var a=b in c;for(;b;)c()`, `for(var a=(b in c);b;)c()`},
 		{`var a=5;while(b)c()`, `for(var a=5;b;)c()`},
+		{`let a=5;while(b)c()`, `let a=5;while(b)c()`},
 		{`a=5;for(var b=4;b;)c()`, `a=5;for(var b=4;b;)c()`},
 		{`a=5;switch(b=4){}`, `switch(a=5,b=4){}`},
 		{`a=5;with(b=4){}`, `with(a=5,b=4);`},

js/stmtlist.go

@@ -150,11 +150,11 @@ func (m *jsMinifier) optimizeStmtList(list []js.IStmt, blockType blockType) []js
 					// merge const, let declarations
 					right.List = append(left.List, right.List...)
 					j--
-				} else if forStmt, ok := list[i].(*js.ForStmt); ok && forStmt.Init == nil {
+				} else if forStmt, ok := list[i].(*js.ForStmt); ok && left.TokenType == js.VarToken && forStmt.Init == nil {
 					// TODO: only merge statements that don't have 'in' or 'of' keywords (slow to check?)
 					forStmt.Init = left
 					j--
-				} else if whileStmt, ok := list[i].(*js.WhileStmt); ok {
+				} else if whileStmt, ok := list[i].(*js.WhileStmt); ok && left.TokenType == js.VarToken {
 					// TODO: only merge statements that don't have 'in' or 'of' keywords (slow to check?)
 					var body js.BlockStmt
 					if blockStmt, ok := whileStmt.Body.(*js.BlockStmt); ok {