objDecl type-checks the declaration of obj in its respective (file) environment. For the meaning of def, see Checker.definedType, in typexpr.go.
(obj Object, def *Named)
| 55 | // objDecl type-checks the declaration of obj in its respective (file) environment. |
| 56 | // For the meaning of def, see Checker.definedType, in typexpr.go. |
| 57 | func (check *Checker) objDecl(obj Object, def *Named) { |
| 58 | if check.conf.Trace && obj.Type() == nil { |
| 59 | if check.indent == 0 { |
| 60 | fmt.Println() // empty line between top-level objects for readability |
| 61 | } |
| 62 | check.trace(obj.Pos(), "-- checking %s (%s, objPath = %s)", obj, obj.color(), pathString(check.objPath)) |
| 63 | check.indent++ |
| 64 | defer func() { |
| 65 | check.indent-- |
| 66 | check.trace(obj.Pos(), "=> %s (%s)", obj, obj.color()) |
| 67 | }() |
| 68 | } |
| 69 | |
| 70 | // Checking the declaration of obj means inferring its type |
| 71 | // (and possibly its value, for constants). |
| 72 | // An object's type (and thus the object) may be in one of |
| 73 | // three states which are expressed by colors: |
| 74 | // |
| 75 | // - an object whose type is not yet known is painted white (initial color) |
| 76 | // - an object whose type is in the process of being inferred is painted grey |
| 77 | // - an object whose type is fully inferred is painted black |
| 78 | // |
| 79 | // During type inference, an object's color changes from white to grey |
| 80 | // to black (pre-declared objects are painted black from the start). |
| 81 | // A black object (i.e., its type) can only depend on (refer to) other black |
| 82 | // ones. White and grey objects may depend on white and black objects. |
| 83 | // A dependency on a grey object indicates a cycle which may or may not be |
| 84 | // valid. |
| 85 | // |
| 86 | // When objects turn grey, they are pushed on the object path (a stack); |
| 87 | // they are popped again when they turn black. Thus, if a grey object (a |
| 88 | // cycle) is encountered, it is on the object path, and all the objects |
| 89 | // it depends on are the remaining objects on that path. Color encoding |
| 90 | // is such that the color value of a grey object indicates the index of |
| 91 | // that object in the object path. |
| 92 | |
| 93 | // During type-checking, white objects may be assigned a type without |
| 94 | // traversing through objDecl; e.g., when initializing constants and |
| 95 | // variables. Update the colors of those objects here (rather than |
| 96 | // everywhere where we set the type) to satisfy the color invariants. |
| 97 | if obj.color() == white && obj.Type() != nil { |
| 98 | obj.setColor(black) |
| 99 | return |
| 100 | } |
| 101 | |
| 102 | switch obj.color() { |
| 103 | case white: |
| 104 | assert(obj.Type() == nil) |
| 105 | // All color values other than white and black are considered grey. |
| 106 | // Because black and white are < grey, all values >= grey are grey. |
| 107 | // Use those values to encode the object's index into the object path. |
| 108 | obj.setColor(grey + color(check.push(obj))) |
| 109 | defer func() { |
| 110 | check.pop().setColor(black) |
| 111 | }() |
| 112 | |
| 113 | case black: |
| 114 | assert(obj.Type() != nil) |
no test coverage detected