bug#23785: Emacs 25: "Undo" overdoes things.

[Alan Mackenzie <acm@muc.de>]

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Hello, Emacs.

Summary: `undo' is broken in Emacs 25.

In GNU Emacs 25.0.94.2 (x86_64-unknown-linux-gnu, GTK+ Version 3.18.7)
 of 2016-06-07 built on acm
Repository revision: 9d5ccebeba0506f7280662630f0ee85a52c8a327
Configured using:
 'configure --with-tiff=no --with-gif=no --with-gpm'

1. emacs -Q
2. C-x C-f decls-6.cc    ; file is attached.
3. Move point to BOL 17.
4. C-o, and insert the line "Type var = init;".  Call this line 16½.
5. M-x revert-buffer.
6. Move point to "[" on L16, and use C-M-k to delete "[3 * peq]".
7. C-_.  This restores "[3 * peq]" (correctly) but also reinserts line
   16½ (which is a bug).

[For reference, the pertinent part of the file looks like this.  In the
actual file "Type" is at column zero:

14.   Type var = init, x = Type();
15.   Type (*var) = init;
16.   Type var[3 * peq] = init;
16½.  Type var = init;         <======== inserted line.
17.   Type (var) = init;
18.   Type int = "int";               // int

].

-- 
Alan Mackenzie (Nuremberg, Germany).


[-- Attachment #2: decls-6.cc --]
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__INLINE__ FOO Type var, x;
__INLINE__ FOO Type *var;
__INLINE__ FOO Type var[3 * peq];

// This is an init paren that currently incorrectly causes the
// variable to be recognized as a function.
__INLINE__ FOO Type var (peq);

__INLINE__ FOO Type var = init, x = Type();
__INLINE__ FOO Type (*var) = init;
__INLINE__ FOO Type var[3 * peq] = init;
__INLINE__ FOO Type var int = "int"; // int

Type var = init, x = Type();
Type (*var) = init;
Type var[3 * peq] = init;
Type (var) = init;
Type int = "int";		// int

const Type var;
const Type (*var);
const Type var[3 * peq];
const Type (var);

Type (*foo) (Type *,
	     Type (*)[x],
	     Type (*var)[x],
	     // An incorrect one that gets "var" recorded as a type.
	     Type (var*)[x],
	     Type &);

Type2 var;
Type var;
Type (*var);			// Currently treated as function call.
Type (*var)[3];
Type var[3 * peq];
Type (var);			// Currently treated as function call.
Type (var)();
::Type var;

unsigned foo bar;
long long x;
long double y;
int x y;			// Invalid
int int y;			// Invalid

// This should be last to check a certain case.
#define low_assign_multiset_index(TO, NODE) do {			\
    struct svalue *_ms_index_to2_ = (TO);				\
  } while (0)