Add code fix to remove unreachable code - #24028
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| const container = (isBlock(statement.parent) ? statement.parent : statement).parent; | ||
| switch (container.kind) { | ||
| case SyntaxKind.IfStatement: | ||
| return (container as IfStatement).elseStatement ? statement : container as IfStatement; |
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if the statement was not in a block, that will leave the the ifStatement syntactically incorrect.. e.g.
if (false) console.log();
else console.log();
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| case SyntaxKind.ForStatement: | ||
| return container as WhileStatement | ForStatement; | ||
| default: | ||
| return statement; |
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you want to return all statemetns from this one untill the end of the block, e.g.:
function f() {
return 0;
// both should be removed, error is only on the first.
var x = 0;
console.log(x);
}
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| break; | ||
| default: | ||
| if (isBlock(statement.parent)) { | ||
| split(sliceAfter(statement.parent.statements, statement), s => !isFunctionDeclaration(s), (start, end) => changes.deleteNodeRange(sourceFile, start, end)); |
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You probably also want to preserve type alias declarations, interfaces, const enums, type only namespaces, var statements, ...
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| // Don't remove statements that can validly be used before they appear. | ||
| return !isFunctionDeclaration(s) && !isPurelyTypeDeclaration(s) && | ||
| // `var x;` may declare a variable used above | ||
| !(isVariableStatement(s) && !(getCombinedNodeFlags(s) & (NodeFlags.Let | NodeFlags.Const)) && s.declarationList.declarations.some(d => !d.initializer)); |
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if it is a var statement it make sure it is not ambient.
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If it's ambient, it should not have an initializer so we won't remove it, right?
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declare let x; would be removed, right?
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Oh, right.
Actually, I can't think of a way a declare statement would be unreachable?
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Andrew Casey (amcasey)
left a comment
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A few questions.
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| newFileContent: | ||
| ` | ||
| // No good way to delete just the 'if' part | ||
| if (false) { } else b; |
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In a perfect world, the output would be b;?
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| case SyntaxKind.IfStatement: | ||
| if ((container as IfStatement).elseStatement) { | ||
| if (isBlock(statement.parent)) { | ||
| changes.deleteNodeRange(sourceFile, first(statement.parent.statements), last(statement.parent.statements)); |
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Don't we want to eliminate the whole else-clause?
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| } | ||
|
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| function shouldRemove(s: Statement): boolean { | ||
| // Don't remove statements that can validly be used before they appear. |
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I'm missing something - why would it be reported as unused if it's used above?
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| split(sliceAfter(statement.parent.statements, statement), shouldRemove, (start, end) => changes.deleteNodeRange(sourceFile, start, end)); | ||
| } | ||
| else { | ||
| changes.deleteNode(sourceFile, statement); |
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Will a switch case ever be reported as unused? Does that need special handling? What about a catch block?
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Mentioned in #24026