Merge pull request #5693 from antlilja/switch-unreachable-else

Add error message for unreachable else prong in switch

1 files changed, 24 insertions, 10 deletions

diff --git a/src/ir.cpp b/src/ir.cpp
index cf8558761f..4a86f57e3b 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -4299,14 +4299,14 @@ static IrInstGen *ir_build_err_to_int_gen(IrAnalyze *ira, Scope *scope, AstNode
 
 static IrInstSrc *ir_build_check_switch_prongs(IrBuilderSrc *irb, Scope *scope, AstNode *source_node,
         IrInstSrc *target_value, IrInstSrcCheckSwitchProngsRange *ranges, size_t range_count,
-        bool have_else_prong, bool have_underscore_prong)
+        AstNode* else_prong, bool have_underscore_prong)
 {
     IrInstSrcCheckSwitchProngs *instruction = ir_build_instruction<IrInstSrcCheckSwitchProngs>(
             irb, scope, source_node);
     instruction->target_value = target_value;
     instruction->ranges = ranges;
     instruction->range_count = range_count;
-    instruction->have_else_prong = have_else_prong;
+    instruction->else_prong = else_prong;
     instruction->have_underscore_prong = have_underscore_prong;
 
     ir_ref_instruction(target_value, irb->current_basic_block);
@@ -9346,7 +9346,7 @@ static IrInstSrc *ir_gen_switch_expr(IrBuilderSrc *irb, Scope *scope, AstNode *n
     }
 
     IrInstSrc *switch_prongs_void = ir_build_check_switch_prongs(irb, scope, node, target_value,
-            check_ranges.items, check_ranges.length, else_prong != nullptr, underscore_prong != nullptr);
+            check_ranges.items, check_ranges.length, else_prong, underscore_prong != nullptr);
 
     IrInstSrc *br_instruction;
     if (cases.length == 0) {
@@ -28827,7 +28827,7 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
                             buf_ptr(enum_field->name)));
                 }
             }
-        } else if (!instruction->have_else_prong) {
+        } else if (instruction->else_prong == nullptr) {
             if (switch_type->data.enumeration.non_exhaustive) {
                 ir_add_error(ira, &instruction->base.base,
                     buf_sprintf("switch on non-exhaustive enum must include `else` or `_` prong"));
@@ -28842,6 +28842,10 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
                             buf_ptr(enum_field->name)));
                 }
             }
+        } else if(!switch_type->data.enumeration.non_exhaustive && switch_type->data.enumeration.src_field_count == instruction->range_count) {
+            ir_add_error_node(ira, instruction->else_prong, 
+                buf_sprintf("unreachable else prong, all cases already handled"));
+            return ira->codegen->invalid_inst_gen;
         }
     } else if (switch_type->id == ZigTypeIdErrorSet) {
         if (!resolve_inferred_error_set(ira->codegen, switch_type, target_value->base.source_node)) {
@@ -28888,7 +28892,7 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
             }
             field_prev_uses[start_index] = start_value->base.source_node;
         }
-        if (!instruction->have_else_prong) {
+        if (instruction->else_prong == nullptr) {
             if (type_is_global_error_set(switch_type)) {
                 ir_add_error(ira, &instruction->base.base,
                     buf_sprintf("else prong required when switching on type 'anyerror'"));
@@ -28950,16 +28954,20 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
                 return ira->codegen->invalid_inst_gen;
             }
         }
-        if (!instruction->have_else_prong) {
+
             BigInt min_val;
             eval_min_max_value_int(ira->codegen, switch_type, &min_val, false);
             BigInt max_val;
             eval_min_max_value_int(ira->codegen, switch_type, &max_val, true);
-            if (!rangeset_spans(&rs, &min_val, &max_val)) {
+        bool handles_all_cases = rangeset_spans(&rs, &min_val, &max_val);
+        if (!handles_all_cases && instruction->else_prong == nullptr) {
                 ir_add_error(ira, &instruction->base.base, buf_sprintf("switch must handle all possibilities"));
                 return ira->codegen->invalid_inst_gen;
+        } else if(handles_all_cases && instruction->else_prong != nullptr) {
+            ir_add_error_node(ira, instruction->else_prong, 
+                buf_sprintf("unreachable else prong, all cases already handled"));
+            return ira->codegen->invalid_inst_gen;
             }
-        }
     } else if (switch_type->id == ZigTypeIdBool) {
         int seenTrue = 0;
         int seenFalse = 0;
@@ -28989,11 +28997,17 @@ static IrInstGen *ir_analyze_instruction_check_switch_prongs(IrAnalyze *ira,
                 return ira->codegen->invalid_inst_gen;
             }
         }
-        if (((seenTrue < 1) || (seenFalse < 1)) && !instruction->have_else_prong) {
+        if (((seenTrue < 1) || (seenFalse < 1)) && instruction->else_prong == nullptr) {
             ir_add_error(ira, &instruction->base.base, buf_sprintf("switch must handle all possibilities"));
             return ira->codegen->invalid_inst_gen;
         }
-    } else if (!instruction->have_else_prong) {
+
+        if(seenTrue == 1 && seenFalse == 1 && instruction->else_prong != nullptr) {
+            ir_add_error_node(ira, instruction->else_prong, 
+                buf_sprintf("unreachable else prong, all cases already handled"));
+            return ira->codegen->invalid_inst_gen;
+        }
+    } else if (instruction->else_prong == nullptr) {
         ir_add_error(ira, &instruction->base.base,
             buf_sprintf("else prong required when switching on type '%s'", buf_ptr(&switch_type->name)));
         return ira->codegen->invalid_inst_gen;