From Jason Turner

[basic.scope.block]

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  ### Block scope <a id="basic.scope.block">[[basic.scope.block]]</a>
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- A name declared in a block [[stmt.block]] is local to that block; it has
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- *block scope*. Its potential scope begins at its point of declaration
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- [[basic.scope.pdecl]] and ends at the end of its block. A variable
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- declared at block scope is a *local variable*.
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-
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- The name declared in an *exception-declaration* is local to the
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- *handler* and shall not be redeclared in the outermost block of the
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- *handler*.
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-
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- Names declared in the *init-statement*, the *for-range-declaration*, and
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- in the *condition* of `if`, `while`, `for`, and `switch` statements are
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- local to the `if`, `while`, `for`, or `switch` statement (including the
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- controlled statement), and shall not be redeclared in a subsequent
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- condition of that statement nor in the outermost block (or, for the `if`
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- statement, any of the outermost blocks) of the controlled statement.
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  [*Example 1*:
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  ``` cpp
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  if (int x = f()) {
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  int x; // error: redeclaration of x
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  }
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  else {
 
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  ### Block scope <a id="basic.scope.block">[[basic.scope.block]]</a>
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+ Each
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+
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+ - selection or iteration statement [[stmt.select]], [[stmt.iter]],
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+ - substatement of such a statement,
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+ - *handler* [[except.pre]], or
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+ - compound statement [[stmt.block]] that is not the *compound-statement*
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+ of a *handler*
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+
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+ introduces a *block scope* that includes that statement or *handler*.
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+
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+ [*Note 1*: A substatement that is also a block has only one
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+ scope. — *end note*]
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+
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+ A variable that belongs to a block scope is a *block variable*.
 
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  [*Example 1*:
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+ ``` cpp
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+ int i = 42;
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+ int a[10];
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+
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+ for (int i = 0; i < 10; i++)
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+ a[i] = i;
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+
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+ int j = i; // j = 42
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+ ```
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+
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+ — *end example*]
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+
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+ If a declaration whose target scope is the block scope S of a
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+
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+ - *compound-statement* of a *lambda-expression*, *function-body*, or
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+ *function-try-block*,
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+ - substatement of a selection or iteration statement that is not itself
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+ a selection or iteration statement, or
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+ - *handler* of a *function-try-block*
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+
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+ potentially conflicts with a declaration whose target scope is the
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+ parent scope of S, the program is ill-formed.
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+
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+ [*Example 2*:
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+
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  ``` cpp
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  if (int x = f()) {
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  int x; // error: redeclaration of x
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  }
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  else {