implement continue expression

closes #6

doc/langref.md

@@ -146,7 +146,7 @@ ArrayAccessExpression : token(LBracket) Expression token(RBracket)
 
 PrefixOp : token(Not) | token(Dash) | token(Tilde) | (token(Ampersand) option(token(Const)))
 
-PrimaryExpression : token(Number) | token(String) | KeywordLiteral | GroupedExpression | Goto | Break | BlockExpression | token(Symbol) | StructValueExpression
+PrimaryExpression : token(Number) | token(String) | KeywordLiteral | GroupedExpression | Goto | token(Break) | token(Continue) | BlockExpression | token(Symbol) | StructValueExpression
 
 StructValueExpression : token(Type) token(LBrace) list(StructValueExpressionField, token(Comma)) token(RBrace)
 
@@ -154,8 +154,6 @@ StructValueExpressionField : token(Dot) token(Symbol) token(Eq) Expression
 
 Goto: token(Goto) token(Symbol)
 
-Break: token(Break)
-
 GroupedExpression : token(LParen) Expression token(RParen)
 
 KeywordLiteral : token(Unreachable) | token(Void) | token(True) | token(False)

src/analyze.cpp

@@ -49,6 +49,7 @@ static AstNode *first_executing_node(AstNode *node) {
         case NodeTypeLabel:
         case NodeTypeGoto:
         case NodeTypeBreak:
+        case NodeTypeContinue:
         case NodeTypeAsmExpr:
         case NodeTypeFieldAccessExpr:
         case NodeTypeStructDecl:
@@ -532,6 +533,7 @@ static void preview_function_declarations(CodeGen *g, ImportTableEntry *import,
         case NodeTypeLabel:
         case NodeTypeGoto:
         case NodeTypeBreak:
+        case NodeTypeContinue:
         case NodeTypeAsmExpr:
         case NodeTypeFieldAccessExpr:
         case NodeTypeStructField:
@@ -601,6 +603,7 @@ static void preview_types(CodeGen *g, ImportTableEntry *import, AstNode *node) {
         case NodeTypeLabel:
         case NodeTypeGoto:
         case NodeTypeBreak:
+        case NodeTypeContinue:
         case NodeTypeAsmExpr:
         case NodeTypeFieldAccessExpr:
         case NodeTypeStructField:
@@ -1381,6 +1384,16 @@ static TypeTableEntry *analyze_break_expr(CodeGen *g, ImportTableEntry *import,
     return g->builtin_types.entry_unreachable;
 }
 
+static TypeTableEntry *analyze_continue_expr(CodeGen *g, ImportTableEntry *import, BlockContext *context,
+        TypeTableEntry *expected_type, AstNode *node)
+{
+    if (!context->break_allowed) {
+        add_node_error(g, node,
+                buf_sprintf("'continue' expression not in loop"));
+    }
+    return g->builtin_types.entry_unreachable;
+}
+
 static TypeTableEntry * analyze_expression(CodeGen *g, ImportTableEntry *import, BlockContext *context,
         TypeTableEntry *expected_type, AstNode *node)
 {
@@ -1463,6 +1476,9 @@ static TypeTableEntry * analyze_expression(CodeGen *g, ImportTableEntry *import,
         case NodeTypeBreak:
             return_type = analyze_break_expr(g, import, context, expected_type, node);
             break;
+        case NodeTypeContinue:
+            return_type = analyze_continue_expr(g, import, context, expected_type, node);
+            break;
         case NodeTypeAsmExpr:
             {
                 node->data.asm_expr.return_count = 0;
@@ -1817,6 +1833,7 @@ static void analyze_top_level_declaration(CodeGen *g, ImportTableEntry *import,
         case NodeTypeLabel:
         case NodeTypeGoto:
         case NodeTypeBreak:
+        case NodeTypeContinue:
         case NodeTypeAsmExpr:
         case NodeTypeFieldAccessExpr:
         case NodeTypeStructField:

src/analyze.hpp

@@ -197,6 +197,7 @@ struct CodeGen {
     LLVMBasicBlockRef cur_basic_block;
     BlockContext *cur_block_context;
     ZigList<LLVMBasicBlockRef> break_block_stack;
+    ZigList<LLVMBasicBlockRef> continue_block_stack;
     bool c_stdint_used;
     AstNode *root_export_decl;
     int version_major;

src/codegen.cpp

@@ -1025,8 +1025,10 @@ static LLVMValueRef gen_while_expr(CodeGen *g, AstNode *node) {
 
     LLVMPositionBuilderAtEnd(g->builder, body_block);
     g->break_block_stack.append(end_block);
+    g->continue_block_stack.append(cond_block);
     gen_expr(g, node->data.while_expr.body);
     g->break_block_stack.pop();
+    g->continue_block_stack.pop();
     if (get_expr_type(node->data.while_expr.body)->id != TypeTableEntryIdUnreachable) {
         LLVMBuildBr(g->builder, cond_block);
     }
@@ -1043,6 +1045,14 @@ static LLVMValueRef gen_break(CodeGen *g, AstNode *node) {
     return LLVMBuildBr(g->builder, dest_block);
 }
 
+static LLVMValueRef gen_continue(CodeGen *g, AstNode *node) {
+    assert(node->type == NodeTypeContinue);
+    LLVMBasicBlockRef dest_block = g->continue_block_stack.last();
+
+    add_debug_source_node(g, node);
+    return LLVMBuildBr(g->builder, dest_block);
+}
+
 static LLVMValueRef gen_expr_no_cast(CodeGen *g, AstNode *node) {
     switch (node->type) {
         case NodeTypeBinOpExpr:
@@ -1174,6 +1184,8 @@ static LLVMValueRef gen_expr_no_cast(CodeGen *g, AstNode *node) {
             return LLVMBuildBr(g->builder, node->codegen_node->data.label_entry->basic_block);
         case NodeTypeBreak:
             return gen_break(g, node);
+        case NodeTypeContinue:
+            return gen_continue(g, node);
         case NodeTypeLabel:
             {
                 LabelTableEntry *label_entry = node->codegen_node->data.label_entry;

src/parser.cpp

@@ -124,6 +124,8 @@ const char *node_type_str(NodeType node_type) {
             return "Goto";
         case NodeTypeBreak:
             return "Break";
+        case NodeTypeContinue:
+            return "Continue";
         case NodeTypeAsmExpr:
             return "AsmExpr";
         case NodeTypeFieldAccessExpr:
@@ -341,6 +343,9 @@ void ast_print(AstNode *node, int indent) {
         case NodeTypeBreak:
             fprintf(stderr, "%s\n", node_type_str(node->type));
             break;
+        case NodeTypeContinue:
+            fprintf(stderr, "%s\n", node_type_str(node->type));
+            break;
         case NodeTypeAsmExpr:
             fprintf(stderr, "%s\n", node_type_str(node->type));
             break;
@@ -1107,7 +1112,7 @@ static AstNode *ast_parse_struct_val_expr(ParseContext *pc, int *token_index) {
 }
 
 /*
-PrimaryExpression : token(Number) | token(String) | KeywordLiteral | GroupedExpression | Goto | Break | BlockExpression | token(Symbol) | StructValueExpression
+PrimaryExpression : token(Number) | token(String) | KeywordLiteral | GroupedExpression | Goto | token(Break) | token(Continue) | BlockExpression | token(Symbol) | StructValueExpression
 */
 static AstNode *ast_parse_primary_expr(ParseContext *pc, int *token_index, bool mandatory) {
     Token *token = &pc->tokens->at(*token_index);
@@ -1165,6 +1170,10 @@ static AstNode *ast_parse_primary_expr(ParseContext *pc, int *token_index, bool
         AstNode *node = ast_create_node(pc, NodeTypeBreak, token);
         *token_index += 1;
         return node;
+    } else if (token->id == TokenIdKeywordContinue) {
+        AstNode *node = ast_create_node(pc, NodeTypeContinue, token);
+        *token_index += 1;
+        return node;
     }
 
     AstNode *grouped_expr_node = ast_parse_grouped_expr(pc, token_index, false);

src/parser.hpp

@@ -49,6 +49,7 @@ enum NodeType {
     NodeTypeLabel,
     NodeTypeGoto,
     NodeTypeBreak,
+    NodeTypeContinue,
     NodeTypeAsmExpr,
     NodeTypeStructDecl,
     NodeTypeStructField,

test/run_tests.cpp

@@ -659,17 +659,15 @@ export fn main(argc : isize, argv : &&u8, env : &&u8) -> i32 {
 }
     )SOURCE", "loop\nloop\nloop\nloop\n");
 
-    add_simple_case("break out of while loop", R"SOURCE(
+    add_simple_case("continue and break", R"SOURCE(
 use "std.zig";
 export fn main(argc : isize, argv : &&u8, env : &&u8) -> i32 {
     var i : i32 = 0;
     while true {
-        while true {
-            if i >= 4 {
-                break;
-            }
-            print_str("loop\n");
-            i += 1;
+        print_str("loop\n");
+        i += 1;
+        if i < 4 {
+            continue;
         }
         break;
     }
@@ -678,6 +676,8 @@ export fn main(argc : isize, argv : &&u8, env : &&u8) -> i32 {
     )SOURCE", "loop\nloop\nloop\nloop\n");
 }
 
+////////////////////////////////////////////////////////////////////////////////////
+
 static void add_compile_failure_test_cases(void) {
     add_compile_fail_case("multiple function definitions", R"SOURCE(
 fn a() {}
@@ -958,6 +958,12 @@ fn f() {
     break;
 }
     )SOURCE", 1, ".tmp_source.zig:3:5: error: 'break' expression not in loop");
+
+    add_compile_fail_case("invalid continue expression", R"SOURCE(
+fn f() {
+    continue;
+}
+    )SOURCE", 1, ".tmp_source.zig:3:5: error: 'continue' expression not in loop");
 }
 
 static void print_compiler_invocation(TestCase *test_case) {