Require body of else-less if expressions to be a value-less block

For consistency with other constructs that could not possibly return a
value (say, loops).

Author: marijnh

src/comp/middle/resolve.rs

@@ -677,7 +677,7 @@ fn lookup_in_scope(e: env, sc: scopes, sp: span, name: ident, ns: namespace)
             if ns == ns_value {
                 alt lookup_in_pat(name, a.pats[0]) {
                   some(did) { ret some(ast::def_binding(did)); }
-                  _ { ret none }
+                  _ { ret none; }
                 }
             }
           }

src/comp/middle/trans.rs

@@ -5130,7 +5130,7 @@ fn trans_closure(bcx_maybe: option::t<@block_ctxt>,
                 create_real_fn_pair(env.bcx, option::get(llfnty), llfndecl,
                                     env.ptr);
             if copying {
-                add_clean_temp(bcx, closure, node_id_type(cx.ccx, id))
+                add_clean_temp(bcx, closure, node_id_type(cx.ccx, id));
             }
             some({fn_pair: closure, bcx: env.bcx})
           }

src/comp/syntax/ext/simplext.rs

@@ -359,7 +359,7 @@ fn transcribe_expr(cx: ext_ctxt, b: bindings, idx_path: @mutable [uint],
           expr_path(p) {
             // Don't substitute into qualified names.
             if vec::len(p.node.types) > 0u || vec::len(p.node.idents) != 1u {
-                e
+                e;
             }
             alt follow_for_trans(cx, b.find(p.node.idents[0]), idx_path) {
               some(match_ident(id)) {

src/comp/syntax/parse/lexer.rs

@@ -194,7 +194,7 @@ fn scan_dec_digits_with_prefix(rdr: reader) -> str {
         rdr.bump();
     }
     let digits = scan_dec_digits(rdr);
-    if negative { str::unshift_char(digits, '-') }
+    if negative { str::unshift_char(digits, '-'); }
     ret digits;
 }
 

src/comp/syntax/parse/parser.rs

@@ -28,6 +28,7 @@ type parser =
         fn swap(token::token, uint, uint);
         fn look_ahead(uint) -> token::token;
         fn fatal(str) -> ! ;
+        fn span_fatal(span, str) -> ! ;
         fn warn(str);
         fn restrict(restriction);
         fn get_restriction() -> restriction;
@@ -99,7 +100,10 @@ fn new_parser(sess: parse_sess, cfg: ast::crate_cfg, rdr: lexer::reader,
             ret buffer[distance - 1u].tok;
         }
         fn fatal(m: str) -> ! {
-            codemap::emit_error(some(self.get_span()), m, sess.cm);
+            self.span_fatal(self.get_span(), m);
+        }
+        fn span_fatal(sp: span, m: str) -> ! {
+            codemap::emit_error(some(sp), m, sess.cm);
             fail;
         }
         fn warn(m: str) {
@@ -1270,6 +1274,9 @@ fn parse_if_expr_1(p: parser) ->
         let elexpr = parse_else_expr(p);
         els = some(elexpr);
         hi = elexpr.span.hi;
+    } else if !option::is_none(thn.node.expr) {
+        let sp = option::get(thn.node.expr).span;
+        p.span_fatal(sp, "if without else can not return a value");
     }
     ret {cond: cond, then: thn, els: els, lo: lo, hi: hi};
 }
@@ -1658,10 +1665,7 @@ fn parse_block_no_value(p: parser) -> ast::blk {
     let blk = parse_block(p);
     if !option::is_none(blk.node.expr) {
         let sp = option::get(blk.node.expr).span;
-        codemap::emit_error(some(sp),
-                            "this block must not return a value",
-                            p.get_sess().cm);
-        fail;
+        p.span_fatal(sp, "this block must not return a value");
     }
     ret blk;
 }

src/comp/syntax/print/pprust.rs

@@ -599,9 +599,9 @@ fn print_maybe_parens_discrim(s: ps, e: @ast::expr) {
       ast::expr_fail(none.) { true }
       _ { false }
     };
-    if disambig { popen(s) }
+    if disambig { popen(s); }
     print_expr(s, e);
-    if disambig { pclose(s) }
+    if disambig { pclose(s); }
 }
 
 fn print_if(s: ps, test: @ast::expr, blk: ast::blk,
@@ -1504,7 +1504,7 @@ fn print_comment(s: ps, cmnt: lexer::cmnt) {
               pp::STRING(s, _) { s == ";" }
               _ { false }
             };
-        if is_semi || is_begin(s) || is_end(s) { hardbreak(s.s) }
+        if is_semi || is_begin(s) || is_end(s) { hardbreak(s.s); }
         hardbreak(s.s);
       }
     }

src/test/compiletest/compiletest.rs

@@ -151,11 +151,11 @@ fn is_test(config: config, testfile: str) -> bool {
     let valid = false;
 
     for ext in valid_extensions {
-        if str::ends_with(name, ext) { valid = true }
+        if str::ends_with(name, ext) { valid = true; }
     }
 
     for pre in invalid_prefixes {
-        if str::starts_with(name, pre) { valid = false }
+        if str::starts_with(name, pre) { valid = false; }
     }
 
     ret valid;

src/test/run-pass/block-expr-precedence.rs

@@ -51,7 +51,7 @@ fn main() {
 
   assert if (true) { 12 } else { 12 } - num == 0;
   assert 12 - if (true) { 12 } else { 12 } == 0;
-  if (true) { 12 } {-num};
-  if (true) { 12 }; {-num};
-  if (true) { 12 };;; -num;
+  if (true) { 12; } {-num};
+  if (true) { 12; }; {-num};
+  if (true) { 12; };;; -num;
 }