add float constraint type

TODO.md

@@ -181,7 +181,29 @@
   - disallow: `b :: undefined` since assigning undefined to something that can't change defeats the purpose
   - disallow assigning `undefined` after declaration; use optionals and `none` for values that intentionally move back to an empty state
 
-13. broaden type inference from surrounding context
+13. introduce a `float` type constraint (similar to `int`) (implemented)
+  - resolves a local binding to any float scalar (`f32`/`f64`) via static analysis; widens
+    `f32` -> `f64` across assignments, mirroring how `int` picks the smallest fitting integer
+  - on a local declaration, integer literals satisfy `float` and default to `f64`
+    (`pi float = 3` is `3.0`); a runtime integer (`x float = some_i32`) stays a
+    `cannot implicitly convert` error
+  - a local initializer whose numeric family doesn't satisfy the constraint now errors for
+    both `int` and `float` instead of silently taking the initializer's natural type
+  - as with `int`, a constraint in a param/result position is a generic passthrough (it
+    forwards the inferred type unchanged, e.g. an identity `func(v int) int` over a range),
+    so the literal-as-float and family checks apply to local bindings, not passthroughs
+
+14. add slice-by-range
+  - allow the use of a range in slice expressions:
+    ```
+    excl_range range :: 0..10
+    some_arr[excl_range] # slice by named exclusive range
+  
+    incl_range range :: 0..=10
+    some_arr[incl_range] # slice by named inclusive range
+    ```
+
+15. broaden type inference from surrounding context
 
 ## A word on multi-unwrap
 

compiler/checker/checker.odin

@@ -1541,7 +1541,7 @@ merge_infer_local_type :: proc(
 		return false
 	}
 	if types.is_constraint(local.declared) {
-		if !types.is_concrete_integer(inferred) {
+		if !types.constraint_accepts(local.declared, inferred) {
 			return false
 		}
 		if !is_runtime_type(checker, local.type) {
@@ -1553,7 +1553,7 @@ merge_infer_local_type :: proc(
 			return false
 		}
 		merged := types.widest(local.type, inferred)
-		if types.is_concrete_integer(merged) {
+		if types.constraint_accepts(local.declared, merged) {
 			local.type = merged
 			record_infer_local_type(local^, local_types)
 			return true
@@ -1605,6 +1605,10 @@ infer_statements :: proc(
 			}
 			if is_runtime_type(checker, declared_local) {
 				value_type = declared_local
+			} else if types.is_constraint(declared_local) {
+				// Seed the binding in-family (INVALID on mismatch, which
+				// build_block reports). FLOAT defaults integers to f64.
+				value_type = types.constraint_target(declared_local, value_type)
 			}
 			local := Infer_Local{
 				name=statement.name,
@@ -1749,6 +1753,9 @@ infer_spec_locals_and_result :: proc(
 	result := types.INVALID
 	infer_statements(checker, function.body, &locals, local_types, function.pkg, function.file, demanded, &result, result_hint)
 	if types.is_constraint(declared) {
+		// Params/results use a constraint as a generic passthrough (e.g. an
+		// identity `func(v int) int` forwarding a range), so the result keeps
+		// the inferred type as-is rather than being narrowed to the family.
 		return local_types, result
 	}
 	return local_types, declared
@@ -2067,6 +2074,25 @@ build_constant_expr :: proc(
 	if types.is_concrete_integer(expected) {
 		recovery_type = expected
 	}
+	// An integer constant in a float context (e.g. `pi float = 3`) folds to a
+	// float literal, mirroring build_float_expr's bit packing.
+	if constant.kind == .Value && types.is_float(expected, checker.target) {
+		fval := f64(constant.value) // ponytail: silent precision loss past 2^53, like C int->double
+		bits := transmute(i64)fval
+		if types.bits(expected, checker.target) == 32 {
+			bits = i64(transmute(u32)f32(fval))
+		}
+		return add_hir_expr(checker, hir.Expr{
+			kind = .Float,
+			span = expr.span,
+			type = expected,
+			integer = bits,
+			target = hir.INVALID_REF,
+			left = hir.INVALID_EXPR,
+			right = hir.INVALID_EXPR,
+			diagnostic = source.INVALID_DIAGNOSTIC,
+		})
+	}
 	if constant.kind == .Div_By_Zero {
 		id := source.add(checker.diagnostics, expr.span, "division by zero in constant expression")
 		return invalid_hir_expr(checker, expr.span, id, recovery_type)
@@ -3427,6 +3453,24 @@ build_block :: proc(
 			   (types.is_constraint(declared) || is_undefined_expr(checker, statement.expr)) {
 				declared = ctx.local_types[statement_id]
 			}
+			// A still-unresolved constraint means the initializer's numeric
+			// family did not satisfy `int`/`float` (`undefined` reports its own).
+			if types.is_constraint(declared) && !is_undefined_expr(checker, statement.expr) {
+				id := source.addf(
+					checker.diagnostics,
+					statement.span,
+					"could not resolve the '%s' constraint for local '%s'",
+					types.name(declared),
+					symbol_text(checker, statement.name),
+				)
+				append(&body, hir.stmt_id(len(checker.module.statements)))
+				append(&checker.module.statements, hir.Stmt{
+					kind = .Trap, span = statement.span, expr = hir.INVALID_EXPR,
+					local = hir.INVALID_LOCAL, diagnostic = id,
+				})
+				ctx.problematic^ = true
+				continue
+			}
 			expected := types.INVALID
 			value := hir.INVALID_EXPR
 			value_type := types.INVALID

compiler/lexer/lexer.odin

@@ -38,6 +38,7 @@ keyword_kind :: proc(text: string) -> token.Kind {
 	case "void":          return .Keyword_Void
 	case "bool":          return .Keyword_Bool
 	case "int":           return .Keyword_Int
+	case "float":         return .Keyword_Float
 	case "i8":            return .Keyword_I8
 	case "i16":           return .Keyword_I16
 	case "i32":           return .Keyword_I32

compiler/parser/parser.odin

@@ -89,7 +89,7 @@ invalid_expr :: proc(parser: ^Parser, span: source.Span, message: string) -> ast
 
 is_type_token :: proc(kind: token.Kind) -> bool {
 	#partial switch kind {
-	case .Keyword_Int, .Keyword_I8, .Keyword_I16, .Keyword_I32, .Keyword_I64,
+	case .Keyword_Int, .Keyword_Float, .Keyword_I8, .Keyword_I16, .Keyword_I32, .Keyword_I64,
 	     .Keyword_U8, .Keyword_U16, .Keyword_U32, .Keyword_U64,
 	     .Keyword_Isize, .Keyword_Usize, .Keyword_F32, .Keyword_F64,
 	     .Keyword_C_Char, .Keyword_C_Schar, .Keyword_C_Uchar,
@@ -216,6 +216,9 @@ parse_type :: proc(parser: ^Parser) -> ast.Type_Syntax {
 	case .Keyword_Int:
 		advance(parser)
 		return types.INT
+	case .Keyword_Float:
+		advance(parser)
+		return types.FLOAT
 	case .Keyword_I8:
 		advance(parser)
 		return types.I8

compiler/token/token.odin

@@ -72,6 +72,7 @@ Kind :: enum u8 {
 	Keyword_Void,
 	Keyword_Bool,
 	Keyword_Int,
+	Keyword_Float,
 	Keyword_I8,
 	Keyword_I16,
 	Keyword_I32,

compiler/types/types.odin

@@ -41,6 +41,7 @@ C_DOUBLE :: Type(27)
 C_LONGDOUBLE :: Type(28)
 
 BOOL :: Type(29)
+FLOAT :: Type(30)
 
 DYNAMIC_START :: Type(64)
 
@@ -55,6 +56,7 @@ Kind :: enum u8 {
 	Invalid,
 	Void,
 	Int_Constraint,
+	Float_Constraint,
 	Scalar,
 	Array,
 	Pointer,
@@ -295,6 +297,8 @@ kind :: proc(value: Type, store: ^Store = nil) -> Kind {
 		return .Void
 	case INT:
 		return .Int_Constraint
+	case FLOAT:
+		return .Float_Constraint
 	case BOOL:
 		return .Scalar
 	}
@@ -334,7 +338,37 @@ is_bool :: proc(value: Type) -> bool {
 }
 
 is_constraint :: proc(value: Type) -> bool {
-	return value == INT
+	return value == INT || value == FLOAT
+}
+
+// constraint_target reports the concrete type a constraint binding takes for an
+// inferred value, or INVALID if the value's numeric family is incompatible.
+// FLOAT accepts integers by defaulting them to f64: a constant integer becomes a
+// float literal in build_constant_expr, while a runtime integer then fails the
+// cross-family f64 coercion in coerce_expr (the intended mismatch error).
+constraint_target :: proc(constraint, inferred: Type) -> Type {
+	switch constraint {
+	case INT:
+		return inferred if is_concrete_integer(inferred) else INVALID
+	case FLOAT:
+		if is_float(inferred) {
+			return inferred
+		}
+		return F64 if is_concrete_integer(inferred) else INVALID
+	}
+	return INVALID
+}
+
+// constraint_accepts reports strict numeric-family membership, used when widening
+// a constraint binding across assignments (no integer-to-float defaulting here).
+constraint_accepts :: proc(constraint, concrete: Type) -> bool {
+	switch constraint {
+	case INT:
+		return is_concrete_integer(concrete)
+	case FLOAT:
+		return is_float(concrete)
+	}
+	return false
 }
 
 is_c :: proc(value: Type) -> bool {
@@ -1140,6 +1174,7 @@ name :: proc(value: Type) -> string {
 	case VOID:          return "void"
 	case BOOL:          return "bool"
 	case INT:           return "int"
+	case FLOAT:         return "float"
 	case I8:            return "i8"
 	case I16:           return "i16"
 	case I32:           return "i32"

compiler_tests.odin

@@ -5136,6 +5136,209 @@ main :: func() void {
 	testing.expect(t, found_value_i16)
 }
 
+float_local_type :: proc(hir_module: ^hir.Module, symbols: ^symbol.Table, function_name, local_name: string) -> (types.Type, bool) {
+	fn_symbol := symbol.intern(symbols, function_name)
+	loc_symbol := symbol.intern(symbols, local_name)
+	for function in hir_module.functions {
+		if function.name != fn_symbol {
+			continue
+		}
+		for local in function.locals {
+			if local.name == loc_symbol {
+				return local.type, true
+			}
+		}
+	}
+	return types.INVALID, false
+}
+
+float_result_type :: proc(hir_module: ^hir.Module, symbols: ^symbol.Table, function_name: string) -> (types.Type, bool) {
+	fn_symbol := symbol.intern(symbols, function_name)
+	for function in hir_module.functions {
+		if function.name == fn_symbol {
+			return function.result, true
+		}
+	}
+	return types.INVALID, false
+}
+
+@(test)
+float_constraint_resolves_to_f64 :: proc(t: ^testing.T) {
+	text := `make :: func() float {
+	pi float = 3.14
+	return pi
+}
+main :: func() void {
+	_ = make()
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	pi_type, found := float_local_type(&hir_module, &symbols, "make", "pi")
+	result_type, _ := float_result_type(&hir_module, &symbols, "make")
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect(t, found)
+	testing.expect_value(t, pi_type, types.F64)
+	testing.expect_value(t, result_type, types.F64)
+}
+
+@(test)
+float_constraint_accepts_integer_literal :: proc(t: ^testing.T) {
+	text := `make :: func() float {
+	pi float = 3
+	return pi
+}
+main :: func() void {
+	_ = make()
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	pi_type, found := float_local_type(&hir_module, &symbols, "make", "pi")
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect(t, found)
+	testing.expect_value(t, pi_type, types.F64)
+}
+
+@(test)
+float_constraint_result_resolves_to_f64 :: proc(t: ^testing.T) {
+	text := `make :: func() float {
+	return 3.0
+}
+main :: func() void {
+	_ = make()
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	result_type, found := float_result_type(&hir_module, &symbols, "make")
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect(t, found)
+	testing.expect_value(t, result_type, types.F64)
+}
+
+@(test)
+float_constraint_widens_f32_to_f64 :: proc(t: ^testing.T) {
+	text := `wide :: func(a f32, b f64) float {
+	x float = a
+	x = b
+	return x
+}
+main :: func() void {
+	_ = wide(1.0, 2.0)
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	x_type, found := float_local_type(&hir_module, &symbols, "wide", "x")
+	result_type, _ := float_result_type(&hir_module, &symbols, "wide")
+
+	testing.expect_value(t, len(diagnostics.items), 0)
+	testing.expect(t, found)
+	testing.expect_value(t, x_type, types.F64)
+	testing.expect_value(t, result_type, types.F64)
+}
+
+@(test)
+int_constraint_rejects_float_initializer :: proc(t: ^testing.T) {
+	text := `main :: func() void {
+	x int = 1.0
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	found_constraint_error := false
+	for diagnostic in diagnostics.items {
+		found_constraint_error = found_constraint_error ||
+			strings.contains(diagnostic.message, "could not resolve the 'int' constraint for local 'x'")
+	}
+
+	testing.expect(t, found_constraint_error)
+}
+
+@(test)
+float_constraint_rejects_runtime_integer :: proc(t: ^testing.T) {
+	text := `take :: func(n i32) void {
+	x float = n
+}
+main :: func() void {
+	take(7)
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	found_convert_error := false
+	for diagnostic in diagnostics.items {
+		found_convert_error = found_convert_error ||
+			strings.contains(diagnostic.message, "cannot implicitly convert i32 to f64")
+	}
+
+	testing.expect(t, found_convert_error)
+}
+
 @(test)
 undefined_accepts_concrete_runtime_annotations :: proc(t: ^testing.T) {
 	text := `Point :: struct {
@@ -5423,11 +5626,11 @@ compound_assignment_preserves_checked_numeric_operations :: proc(t: ^testing.T)
 	unsigned -= 2
 	unsigned *= 3
 	unsigned /= 4
-	float f64 = 24.0
+	real f64 = 24.0
-	float += 6.0
+	real += 6.0
-	float -= 2.0
+	real -= 2.0
-	float *= 3.0
+	real *= 3.0
-	float /= 4.0
+	real /= 4.0
 	return signed
 }
 `