Merge pull request #1857 from vegecode/boolean-switch

Switching on bools with duplicate and missing value detection: Issue …

Author: andrewrk

src/ir.cpp

@@ -19787,6 +19787,39 @@ static IrInstruction *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
                 return ira->codegen->invalid_instruction;
             }
         }
+    } else if (switch_type->id == ZigTypeIdBool) {
+        int seenTrue = 0;
+        int seenFalse = 0;
+        for (size_t range_i = 0; range_i < instruction->range_count; range_i += 1) {
+            IrInstructionCheckSwitchProngsRange *range = &instruction->ranges[range_i];
+
+            IrInstruction *value = range->start->child;
+
+            IrInstruction *casted_value = ir_implicit_cast(ira, value, switch_type);
+            if (type_is_invalid(casted_value->value.type))
+                return ira->codegen->invalid_instruction;
+
+            ConstExprValue *const_expr_val = ir_resolve_const(ira, casted_value, UndefBad);
+            if (!const_expr_val)
+                return ira->codegen->invalid_instruction;
+
+            assert(const_expr_val->type->id == ZigTypeIdBool);
+
+            if (const_expr_val->data.x_bool == true) {
+                seenTrue += 1;
+            } else {
+                seenFalse += 1;
+            }
+            
+            if ((seenTrue > 1) || (seenFalse > 1)) {
+                ir_add_error(ira, value, buf_sprintf("duplicate switch value"));
+                return ira->codegen->invalid_instruction;
+            }
+        }
+        if (((seenTrue < 1) || (seenFalse < 1)) && !instruction->have_else_prong) {
+            ir_add_error(ira, &instruction->base, buf_sprintf("switch must handle all possibilities"));
+            return ira->codegen->invalid_instruction;
+        }
     } else if (!instruction->have_else_prong) {
         ir_add_error(ira, &instruction->base,
             buf_sprintf("else prong required when switching on type '%s'", buf_ptr(&switch_type->name)));

test/cases/switch.zig

@@ -232,3 +232,40 @@ test "capture value of switch with all unreachable prongs" {
     };
     assert(x == 1);
 }
+
+test "switching on booleans" {
+    testSwitchOnBools();
+    comptime testSwitchOnBools();
+}
+
+fn testSwitchOnBools() void {
+    assert(testSwitchOnBoolsTrueAndFalse(true) == false);
+    assert(testSwitchOnBoolsTrueAndFalse(false) == true);
+
+    assert(testSwitchOnBoolsTrueWithElse(true) == false);
+    assert(testSwitchOnBoolsTrueWithElse(false) == true);
+
+    assert(testSwitchOnBoolsFalseWithElse(true) == false);
+    assert(testSwitchOnBoolsFalseWithElse(false) == true);
+}
+
+fn testSwitchOnBoolsTrueAndFalse(x: bool) bool {
+    return switch (x) {
+        true => false,
+        false => true,
+    };
+}
+
+fn testSwitchOnBoolsTrueWithElse(x: bool) bool {
+    return switch (x) {
+        true => false,
+        else => true,
+    };
+}
+
+fn testSwitchOnBoolsFalseWithElse(x: bool) bool {
+    return switch (x) {
+        false => true,
+        else => false,
+    };
+}

test/compile_errors.zig

@@ -1,6 +1,44 @@
 const tests = @import("tests.zig");
 
 pub fn addCases(cases: *tests.CompileErrorContext) void {
+    cases.add(
+        "duplicate boolean switch value",
+        \\comptime {
+        \\    const x = switch (true) {
+        \\        true => false,
+        \\        false => true,
+        \\        true => false,
+        \\    };
+        \\}
+        \\comptime {
+        \\    const x = switch (true) {
+        \\        false => true,
+        \\        true => false,
+        \\        false => true,
+        \\    };
+        \\}
+    ,
+        ".tmp_source.zig:5:9: error: duplicate switch value",
+        ".tmp_source.zig:12:9: error: duplicate switch value",
+    );
+
+    cases.add(
+        "missing boolean switch value",
+        \\comptime {
+        \\    const x = switch (true) {
+        \\        true => false,
+        \\    };
+        \\}
+        \\comptime {
+        \\    const x = switch (true) {
+        \\        false => true,
+        \\    };
+        \\}
+    ,
+        ".tmp_source.zig:2:15: error: switch must handle all possibilities",
+        ".tmp_source.zig:7:15: error: switch must handle all possibilities",
+    );
+
     cases.add(
         "reading past end of pointer casted array",
         \\comptime {