Add type hints to mk2rbc

Type hints have the format #RBC# type_hint MY_VAR list
and must be specified at the top of the Makefile. Setting
one will cause that variable to have that type for the
remainder of the Makefile. This can be used where mk2rbc's
type inference detects the wrong type and it must be
manually changed.

Bug: 224601891
Test: go test
Change-Id: I6db2c50056d0298227e1d2801a522adf8bbd1df8

1 files changed, 10 insertions, 4 deletions

diff --git a/mk2rbc/variable.go b/mk2rbc/variable.go
index 6805744a7..69297b94d 100644
--- a/mk2rbc/variable.go
+++ b/mk2rbc/variable.go
@@ -291,6 +291,12 @@ var presetVariables = map[string]bool{
 // addVariable returns a variable with a given name. A variable is
 // added if it does not exist yet.
 func (ctx *parseContext) addVariable(name string) variable {
+	// Get the hintType before potentially changing the variable name
+	var hintType starlarkType
+	var ok bool
+	if hintType, ok = ctx.typeHints[name]; !ok {
+		hintType = starlarkTypeUnknown
+	}
 	// Heuristics: if variable's name is all lowercase, consider it local
 	// string variable.
 	isLocalVariable := name == strings.ToLower(name)
@@ -301,8 +307,8 @@ func (ctx *parseContext) addVariable(name string) variable {
 	}
 	v, found := ctx.variables[name]
 	if !found {
-		_, preset := presetVariables[name]
 		if vi, found := KnownVariables[name]; found {
+			_, preset := presetVariables[name]
 			switch vi.class {
 			case VarClassConfig:
 				v = &productConfigVariable{baseVariable{nam: name, typ: vi.valueType, preset: preset}}
@@ -310,10 +316,10 @@ func (ctx *parseContext) addVariable(name string) variable {
 				v = &otherGlobalVariable{baseVariable{nam: name, typ: vi.valueType, preset: preset}}
 			}
 		} else if isLocalVariable {
-			v = &localVariable{baseVariable{nam: name, typ: starlarkTypeUnknown}}
+			v = &localVariable{baseVariable{nam: name, typ: hintType}}
 		} else {
-			vt := starlarkTypeUnknown
-			if strings.HasPrefix(name, "LOCAL_") {
+			vt := hintType
+			if strings.HasPrefix(name, "LOCAL_") && vt == starlarkTypeUnknown {
 				// Heuristics: local variables that contribute to corresponding config variables
 				if cfgVarName, found := localProductConfigVariables[name]; found {
 					vi, found2 := KnownVariables[cfgVarName]