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Allow implicit bounds on slices.

--- a/parse/gram.y

+++ b/parse/gram.y

@@ -133,7 +133,7 @@

 %type <node> bandexpr cmpexpr unionexpr addexpr mulexpr shiftexpr prefixexpr postfixexpr

 %type <node> funclit seqlit name block stmt label use

 %type <node> decl declbody declcore structelt seqelt tuphead

-%type <node> ifstmt forstmt whilestmt matchstmt elifs optexprln

+%type <node> ifstmt forstmt whilestmt matchstmt elifs optexprln optexpr

 %type <node> pat unionpat match

 %type <node> castexpr

 %type <ucon> unionelt

@@ -381,6 +381,14 @@

             {$$ = mkexpr($1->line, Oret, NULL);}

         ;

+optexpr : expr {$$ = $1;}

+        | /* empty */ {$$ = NULL;}

+        ;

+

+optexprln: exprln {$$ = $1;}

+         | Tendln {$$ = NULL;}

+         ;

+

 exprln  : expr Tendln

         ;

@@ -494,8 +502,8 @@

             {$$ = mkexpr($1->line, Opostdec, $1, NULL);}

         | postfixexpr Tosqbrac expr Tcsqbrac

             {$$ = mkexpr($1->line, Oidx, $1, $3, NULL);}

-        | postfixexpr Tosqbrac expr Tcomma expr Tcsqbrac

-            {$$ = mkexpr($1->line, Oslice, $1, $3, $5, NULL);}

+        | postfixexpr Tosqbrac optexpr Tcomma optexpr Tcsqbrac

+            {$$ = mksliceexpr($1->line, $1, $3, $5);}

         | postfixexpr Toparen arglist Tcparen

             {$$ = mkcall($1->line, $1, $3.nl, $3.nn);}

         | atomicexpr

@@ -601,10 +609,6 @@

         | Tfor decl Tendln optexprln optexprln block

             {$$ = mkloopstmt($1->line, $2, $4, $5, $6);}

         ;

-

-optexprln: exprln {$$ = $1;}

-         | Tendln {$$ = NULL;}

-         ;

 whilestmt

         : Twhile exprln block

--- a/parse/node.c

+++ b/parse/node.c

@@ -46,6 +46,15 @@

     return n;

 }

+Node *mksliceexpr(int line, Node *sl, Node *base, Node *off)

+{

+    if (!base)

+        base = mkintlit(line, 0);

+    if (!off)

+        off = mkexpr(line, Omemb, sl, mkname(line, "len"), NULL);

+    return mkexpr(line, Oslice, sl, base, off, NULL);

+}

+

 Node *mkexprl(int line, Op op, Node **args, size_t nargs)

 {

     Node *n;

@@ -359,4 +368,3 @@

 {

     return did(a) == did(b);

 }

-

--- a/parse/parse.h

+++ b/parse/parse.h

@@ -363,6 +363,7 @@

 Node *mknode(int line, Ntype nt);

 Node *mkfile(char *name);

 Node *mkuse(int line, char *use, int islocal);

+Node *mksliceexpr(int line, Node *sl, Node *base, Node *off);

 Node *mkexprl(int line, Op op, Node **args, size_t nargs);

 Node *mkexpr(int line, Op op, ...); /* NULL terminated */

 Node *mkcall(int line, Node *fn, Node **args, size_t nargs);

--- a/test/slice.myr

+++ b/test/slice.myr

@@ -2,9 +2,9 @@

 	var a : int[3]

 	var s

-	s = a[0,3]

+	s = a[,]

 	s[0] = 3

 	s[1] = 4

-	s[2] = s[0] + s[1]

+	s[2] = s[0] + s[1] + s.len

 	-> s[2]

 }

--- a/test/tests

+++ b/test/tests

@@ -36,7 +36,7 @@

 B arrayaddr	E	42

 B global-arrayvar	E	7

 B arraylen	E	12

-B slice		E	7

+B slice		E	10

 B slicelen	E	5

 B call		E	42

 B voidcall	E	12