nullish coalescing operator ??

3 files changed, 34 insertions, 13 deletions

diff --git a/bootstrap/cgen.c b/bootstrap/cgen.c
index 665bdc5..15fab93 100644
--- a/bootstrap/cgen.c
+++ b/bootstrap/cgen.c
@@ -222,7 +222,7 @@ genexpr(struct expr *ex) {
       pri("(%e)%c", ex->unop.child, ex->unop.op);
       break;
    case Ebinop:
-      pri("(%e %c %e)", ex->binop.lhs, ex->binop.op, ex->binop.rhs);
+      pri("((%e) %c (%e))", ex->binop.lhs, ex->binop.op == '?\?' ? '?:' : ex->binop.op, ex->binop.rhs);
       break;
    case Econd:
       pri("((%e) ? (%e) : (%e))", ex->cond.test, ex->cond.t, ex->cond.f);
diff --git a/bootstrap/parse.c b/bootstrap/parse.c
index 08f83a8..2eda662 100644
--- a/bootstrap/parse.c
+++ b/bootstrap/parse.c
@@ -439,9 +439,13 @@ lex(struct parser *P) {
    switch ((c = chr(P))) {
    case '(': case ')': case '[': case ']':
    case '{': case '}': case ',':
-   case ';': case '?': case '~':
+   case ';': case '~':
       tok.t = c;
       return tok;
+   case '?':
+      if (chrmatch(P, '?')) tok.t = '\?\?';
+      else                  tok.t = '?';
+      return tok;
    case '.':
       if (chrmatch(P, '.')) {
          if (chr(P) != '.')
@@ -1720,20 +1724,33 @@ pexlog(struct parser *P) {
    if (P->used_targty) return ex;
    tok = lexpeek(P);
    tokt = tok.t;
-   if (tokt != TKkw_and && tokt != TKkw_or)
+   if (tokt != TKkw_and && tokt != TKkw_or && tokt != '?\?')
       return ex;
    
    while (lexmatch(P, &tok, tokt)) {
       struct expr rhs = pexcmp(P);
-      if (ex.ty->t != TYbool || rhs.ty->t != TYbool)
-         fatal(P, tok.span,
-               "invalid operands %t and %t to binary operator %k",
+      if (tokt == '?\?') {
+         const struct type *ty = typeof2(ex.ty, rhs.ty);
+         if (ex.ty->t != TYptr || rhs.ty->t != TYptr || !ty)
+            fatal(P, tok.span,
+                  "invalid operands %t and %t to binary operator %k",
                ex.ty, rhs.ty, tok.t);
-      ex = (struct expr) {
-         Ebinop, tok.span, ty_bool, .binop = {
-            tokt == TKkw_and ? 'and' : 'or', exprdup(ex), exprdup(rhs)
-         }
-      };
+         ex = (struct expr) {
+            Ebinop, tok.span, ty, .binop = {
+               '?\?', exprdup(ex), exprdup(rhs)
+            }
+         };
+      } else {
+         if (ex.ty->t != TYbool || rhs.ty->t != TYbool)
+            fatal(P, tok.span,
+                  "invalid operands %t and %t to binary operator %k",
+               ex.ty, rhs.ty, tok.t);
+         ex = (struct expr) {
+            Ebinop, tok.span, ty_bool, .binop = {
+               tokt == TKkw_and ? 'and' : 'or', exprdup(ex), exprdup(rhs)
+            }
+         };
+      }
 
    }
 
diff --git a/src/parse.cff b/src/parse.cff
index c331986..87ca850 100644
--- a/src/parse.cff
+++ b/src/parse.cff
@@ -414,9 +414,13 @@ fn lex(P *Parser) Tok {
    }
    switch c = chr(P) {
    case '(', ')', '[', ']', '{',
-        '}', ',', ';', '?', '~';
+        '}', ',', ';', '~';
       tok.t = c;
       return tok;
+   case '?';
+      if chrmatch(P, '?') { tok.t = '??'; }
+      else                { tok.t = '?'; }
+      return tok;
    case '.';
       if chrmatch(P, '.') {
          if chrmatch(P, '.') { tok.t = '...'; }
@@ -541,7 +545,7 @@ fn finddecl(P *Parser, name *const u8) *Decl {
       putprimtypes(primenv);
    }
    let p = envfind(primenv, name);
-   return p ? p : envfind(P.curenv, name);
+   return p ?? envfind(P.curenv, name);
 }
 
 fn putdecl(P *Parser, decl Decl) *Decl {