Exhaustive switch on enums. This addresses #838

lib/std/core/allocators/arena_allocator.c3

@@ -79,7 +79,6 @@ fn void*! arena_allocator_function(Allocator* data, usz size, usz alignment, usz
 			arena.used = size;
 			return null;
 	}
-	unreachable();
 }
 
 /**

lib/std/core/allocators/dynamic_arena.c3

@@ -237,5 +237,4 @@ fn void*! dynamic_arena_allocator_function(Allocator* data, usz size, usz alignm
 			allocator.reset();
 			return null;
 	}
-	unreachable();
 }

lib/std/core/allocators/on_stack_allocator.c3

@@ -97,7 +97,6 @@ fn void*! on_stack_allocator_function(Allocator* data, usz size, usz alignment,
 		case RESET:
 			unreachable("Reset unsupported");
 	}
-	unreachable();
 }
 
 fn bool allocation_in_stack_mem(OnStackAllocator* a, void* ptr) @local

lib/std/core/allocators/temp_allocator.c3

@@ -83,7 +83,6 @@ fn void*! temp_allocator_function(Allocator* data, usz size, usz alignment, usz
 			arena._reset(size)!;
 			return null;
 	}
-	unreachable();
 }
 
 fn void! TempAllocator._free(&self, void* old_pointer) @local

lib/std/core/allocators/tracking_allocator.c3

@@ -104,5 +104,4 @@ fn void*! tracking_allocator_fn(Allocator* data, usz size, usz alignment, usz of
 			this.map.clear();
 			return null;
 	}
-	unreachable();
 }

lib/std/encoding/json.c3

@@ -69,7 +69,6 @@ fn Object*! JsonParser.parse_from_token(&self, JsonTokenType token)
 		case NULL: return object::new_null();
 		case EOF: return JsonParsingError.EOF?;
 	}
-	unreachable();
 }
 fn Object*! JsonParser.parse_any(&self)
 {

releasenotes.md

@@ -3,6 +3,7 @@
 ## 0.5.0 Change List
 
 ### Changes / improvements
+- Exhaustive switches with enums has better analysis.
 - Globals may now be initialized with optional values.
 - New generic syntax.
 - Added `$embed` to embed binary data.

src/compiler/sema_stmts.c

@@ -2110,8 +2110,10 @@ static bool sema_analyse_switch_body(SemaContext *context, Ast *statement, Sourc
 		return false;
 	}
 	// We need an if-chain if this isn't an enum/integer type.
-	TypeKind flat_switch_type_kind = type_flatten(switch_type)->type_kind;
-	bool if_chain = flat_switch_type_kind != TYPE_ENUM && !type_kind_is_any_integer(flat_switch_type_kind);
+	Type *flat = type_flatten(switch_type);
+	TypeKind flat_switch_type_kind = flat->type_kind;
+	bool is_enum_switch = flat_switch_type_kind == TYPE_ENUM;
+	bool if_chain = !is_enum_switch && !type_kind_is_any_integer(flat_switch_type_kind);
 
 	Ast *default_case = NULL;
 	assert(context->active_scope.defer_start == context->active_scope.defer_last);
@@ -2163,6 +2165,7 @@ static bool sema_analyse_switch_body(SemaContext *context, Ast *statement, Sourc
 		POP_NEXT();
 	}
 
+	if (!exhaustive && is_enum_switch && case_count == vec_size(flat->decl->enums.values)) exhaustive = true;
 	bool all_jump_end = exhaustive;
 	for (unsigned i = 0; i < case_count; i++)
 	{

test/test_suite/statements/exhaustive_switch.c3t

@@ -0,0 +1,39 @@
+// #target: macos-x64
+module test;
+import std::io;
+
+enum Foo
+{
+	ABC,
+	DEF
+}
+
+fn int hello(Foo a)
+{
+	switch (a)
+	{
+		case ABC: return 1;
+		case DEF: return 0;
+	}
+}
+
+/* #expect: test.ll
+
+define i32 @test.hello(i32 %0) #0 {
+entry:
+  %switch = alloca i32, align 4
+  store i32 %0, ptr %switch, align 4
+  br label %switch.entry
+switch.entry:                                     ; preds = %entry
+  %1 = load i32, ptr %switch, align 4
+  switch i32 %1, label %switch.exit [
+    i32 0, label %switch.case
+    i32 1, label %switch.case1
+  ]
+switch.case:                                      ; preds = %switch.entry
+  ret i32 1
+switch.case1:                                     ; preds = %switch.entry
+  ret i32 0
+switch.exit:                                      ; preds = %switch.entry
+  unreachable
+}