add float constraint type

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"